Monomorphic processing of TopN queries with 1 and 2 aggregators (key part of #3798) (#3889)

* Monomorphic processing: add HotLoopCallee, CalledFromHotLoop, RuntimeShapeInspector, SpecializationService. Specialize topN queries with 1 or 2 aggregators. Add Cursor.advanceUninterruptibly() and isDoneOrInterrupted() for exception-free query processing.

* Use Execs.singleThreaded()

* RuntimeShapeInspector to support nullable fields

* Make CalledFromHotLoop annotation Inherited

* Remove unnecessary conversion of array of ColumnSelectorPluses to list and back to array in CardinalityAggregatorFactory

* Close InputStream in SpecializationService

* Formatting

* Test specialized PooledTopNScanners

* Set flags in PooledTopNAlgorithm directly

* Fix tests, dependent on CountAggragatorFactory toString() form

* Fix

* Revert CountAggregatorFactory changes

* Implement inspectRuntimeShape() for LongWrappingDimensionSelector and FloatWrappingDimensionSelector

* Remove duplicate RoaringBitmap dependency in the extendedset pom.xml

* Fix

* Treat ByteBuffers specially in StringRuntimeShape

* Doc fix

* Annotate BufferAggregator.init() with CalledFromHotLoop

* Make triggerSpecializationIterationsThreshold an int

* Remove SpecializationService.PerPrototypeClassState.of()

* Add comments

* Limit the amount of specializations that SpecializationService could make

* Add default implementation for BufferAggregator.inspectRuntimeShape(), for compatibility with extensions

* Use more efficient ConcurrentMap's idioms in SpecializationService

extensions-contrib/distinctcount/src/main/java/io/druid/query/aggregation/distinctcount/DistinctCountAggregatorFactory.java

@@ -83,7 +83,7 @@ public class DistinctCountAggregatorFactory extends AggregatorFactory
   {
     DimensionSelector selector = makeDimensionSelector(columnFactory);
     if (selector == null) {
-      return new EmptyDistinctCountBufferAggregator();
+      return EmptyDistinctCountBufferAggregator.instance();
     } else {
       return new DistinctCountBufferAggregator(makeDimensionSelector(columnFactory));
     }

extensions-contrib/distinctcount/src/main/java/io/druid/query/aggregation/distinctcount/DistinctCountBufferAggregator.java

@@ -22,16 +22,17 @@ package io.druid.query.aggregation.distinctcount;
 import io.druid.collections.bitmap.MutableBitmap;
 import io.druid.collections.bitmap.WrappedRoaringBitmap;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.DimensionSelector;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
 
 import java.nio.ByteBuffer;
-import java.util.HashMap;
-import java.util.Map;
 
 public class DistinctCountBufferAggregator implements BufferAggregator
 {
   private final DimensionSelector selector;
-  private final Map<Integer, MutableBitmap> mutableBitmapCollection = new HashMap<>();
+  private final Int2ObjectMap<MutableBitmap> mutableBitmapCollection = new Int2ObjectOpenHashMap<>();
 
   public DistinctCountBufferAggregator(
       DimensionSelector selector
@@ -89,4 +90,10 @@ public class DistinctCountBufferAggregator implements BufferAggregator
   {
     mutableBitmapCollection.clear();
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+  }
 }

extensions-contrib/distinctcount/src/main/java/io/druid/query/aggregation/distinctcount/EmptyDistinctCountBufferAggregator.java

@@ -20,13 +20,24 @@
 package io.druid.query.aggregation.distinctcount;
 
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 
 import java.nio.ByteBuffer;
 
-public class EmptyDistinctCountBufferAggregator implements BufferAggregator
+/**
+ * The difference from {@link io.druid.query.aggregation.NoopBufferAggregator} is that
+ * EmptyDistinctCountBufferAggregator returns 0 instead of null from {@link #get(ByteBuffer, int)}.
+ */
+public final class EmptyDistinctCountBufferAggregator implements BufferAggregator
 {
+  private static final EmptyDistinctCountBufferAggregator INSTANCE = new EmptyDistinctCountBufferAggregator();
 
-  public EmptyDistinctCountBufferAggregator()
+  static EmptyDistinctCountBufferAggregator instance()
+  {
+    return INSTANCE;
+  }
+
+  private EmptyDistinctCountBufferAggregator()
   {
   }
 
@@ -62,4 +73,9 @@ public class EmptyDistinctCountBufferAggregator implements BufferAggregator
   public void close()
   {
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+  }
 }

extensions-contrib/time-min-max/src/main/java/io/druid/query/aggregation/TimestampBufferAggregator.java

@@ -20,6 +20,7 @@
 package io.druid.query.aggregation;
 
 import io.druid.data.input.impl.TimestampSpec;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ObjectColumnSelector;
 
 import java.nio.ByteBuffer;
@@ -79,7 +80,14 @@ public class TimestampBufferAggregator implements BufferAggregator
   }
 
   @Override
-  public void close() {
+  public void close()
+  {
+  }
 
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+    inspector.visit("comparator", comparator);
   }
 }

extensions-core/datasketches/src/main/java/io/druid/query/aggregation/datasketches/theta/EmptySketchBufferAggregator.java

@@ -20,12 +20,20 @@
 package io.druid.query.aggregation.datasketches.theta;
 
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 
 import java.nio.ByteBuffer;
 
-public class EmptySketchBufferAggregator implements BufferAggregator
+public final class EmptySketchBufferAggregator implements BufferAggregator
 {
-  public EmptySketchBufferAggregator()
+  private static final EmptySketchBufferAggregator INSTANCE = new EmptySketchBufferAggregator();
+
+  public static EmptySketchBufferAggregator instance()
+  {
+    return INSTANCE;
+  }
+
+  private EmptySketchBufferAggregator()
   {
   }
 
@@ -61,4 +69,9 @@ public class EmptySketchBufferAggregator implements BufferAggregator
   public void close()
   {
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+  }
 }

extensions-core/datasketches/src/main/java/io/druid/query/aggregation/datasketches/theta/SketchAggregatorFactory.java

@@ -73,7 +73,7 @@ public abstract class SketchAggregatorFactory extends AggregatorFactory
   {
     ObjectColumnSelector selector = metricFactory.makeObjectColumnSelector(fieldName);
     if (selector == null) {
-      return new EmptySketchBufferAggregator();
+      return EmptySketchBufferAggregator.instance();
     } else {
       return new SketchBufferAggregator(selector, size, getMaxIntermediateSize());
     }

extensions-core/datasketches/src/main/java/io/druid/query/aggregation/datasketches/theta/SketchBufferAggregator.java

@@ -26,6 +26,7 @@ import com.yahoo.sketches.Family;
 import com.yahoo.sketches.theta.SetOperation;
 import com.yahoo.sketches.theta.Union;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ObjectColumnSelector;
 
 import java.nio.ByteBuffer;
@@ -113,4 +114,9 @@ public class SketchBufferAggregator implements BufferAggregator
     unions.clear();
   }
 
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+  }
 }

extensions-core/histogram/src/main/java/io/druid/query/aggregation/histogram/ApproximateHistogramBufferAggregator.java

@@ -20,6 +20,7 @@
 package io.druid.query.aggregation.histogram;
 
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.FloatColumnSelector;
 
 import java.nio.ByteBuffer;
@@ -99,4 +100,10 @@ public class ApproximateHistogramBufferAggregator implements BufferAggregator
   {
     // no resources to cleanup
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+  }
 }

extensions-core/histogram/src/main/java/io/druid/query/aggregation/histogram/ApproximateHistogramFoldingBufferAggregator.java

@@ -20,6 +20,7 @@
 package io.druid.query.aggregation.histogram;
 
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ObjectColumnSelector;
 
 import java.nio.ByteBuffer;
@@ -102,4 +103,10 @@ public class ApproximateHistogramFoldingBufferAggregator implements BufferAggreg
   {
     // no resources to cleanup
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+  }
 }

extensions-core/stats/src/main/java/io/druid/query/aggregation/variance/VarianceAggregatorFactory.java

@@ -23,14 +23,14 @@ import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import com.google.common.base.Preconditions;
-
 import io.druid.java.util.common.IAE;
 import io.druid.java.util.common.StringUtils;
 import io.druid.query.aggregation.Aggregator;
 import io.druid.query.aggregation.AggregatorFactory;
 import io.druid.query.aggregation.AggregatorFactoryNotMergeableException;
-import io.druid.query.aggregation.Aggregators;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.aggregation.NoopAggregator;
+import io.druid.query.aggregation.NoopBufferAggregator;
 import io.druid.segment.ColumnSelectorFactory;
 import io.druid.segment.ObjectColumnSelector;
 import org.apache.commons.codec.binary.Base64;
@@ -95,7 +95,7 @@ public class VarianceAggregatorFactory extends AggregatorFactory
   {
     ObjectColumnSelector selector = metricFactory.makeObjectColumnSelector(fieldName);
     if (selector == null) {
-      return Aggregators.noopAggregator();
+      return NoopAggregator.instance();
     }
 
     if ("float".equalsIgnoreCase(inputType)) {
@@ -115,7 +115,7 @@ public class VarianceAggregatorFactory extends AggregatorFactory
   {
     ObjectColumnSelector selector = metricFactory.makeObjectColumnSelector(fieldName);
     if (selector == null) {
-      return Aggregators.noopBufferAggregator();
+      return NoopBufferAggregator.instance();
     }
     if ("float".equalsIgnoreCase(inputType)) {
       return new VarianceBufferAggregator.FloatVarianceAggregator(

extensions-core/stats/src/main/java/io/druid/query/aggregation/variance/VarianceBufferAggregator.java

@@ -22,6 +22,7 @@ package io.druid.query.aggregation.variance;
 import com.google.common.primitives.Doubles;
 import com.google.common.primitives.Longs;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.FloatColumnSelector;
 import io.druid.segment.LongColumnSelector;
 import io.druid.segment.ObjectColumnSelector;
@@ -102,6 +103,12 @@ public abstract class VarianceBufferAggregator implements BufferAggregator
         buf.putDouble(position + NVARIANCE_OFFSET, variance);
       }
     }
+
+    @Override
+    public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+    {
+      inspector.visit("selector", selector);
+    }
   }
 
   public static final class LongVarianceAggregator extends VarianceBufferAggregator
@@ -128,6 +135,12 @@ public abstract class VarianceBufferAggregator implements BufferAggregator
         buf.putDouble(position + NVARIANCE_OFFSET, variance);
       }
     }
+
+    @Override
+    public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+    {
+      inspector.visit("selector", selector);
+    }
   }
 
   public static final class ObjectVarianceAggregator extends VarianceBufferAggregator
@@ -167,5 +180,11 @@ public abstract class VarianceBufferAggregator implements BufferAggregator
       buf.putDouble(position + SUM_OFFSET, sum);
       buf.putDouble(position + NVARIANCE_OFFSET, nvariance);
     }
+
+    @Override
+    public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+    {
+      inspector.visit("selector", selector);
+    }
   }
 }

extensions-core/stats/src/test/java/io/druid/query/aggregation/variance/VarianceAggregatorCollectorTest.java

@@ -20,10 +20,9 @@
 package io.druid.query.aggregation.variance;
 
 import com.google.common.collect.Lists;
-
 import io.druid.java.util.common.Pair;
-import io.druid.segment.FloatColumnSelector;
 import io.druid.segment.ObjectColumnSelector;
+import io.druid.segment.TestFloatColumnSelector;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -142,7 +141,7 @@ public class VarianceAggregatorCollectorTest
     }
   }
 
-  private static class FloatHandOver implements FloatColumnSelector
+  private static class FloatHandOver extends TestFloatColumnSelector
   {
     float v;
 

extensions-core/stats/src/test/java/io/druid/query/aggregation/variance/VarianceTopNQueryTest.java

@@ -54,7 +54,7 @@ public class VarianceTopNQueryTest
   @Parameterized.Parameters(name="{0}")
   public static Iterable<Object[]> constructorFeeder() throws IOException
   {
-    return TopNQueryRunnerTest.constructorFeeder();
+    return QueryRunnerTestHelper.transformToConstructionFeeder(TopNQueryRunnerTest.queryRunners());
   }
 
   private final QueryRunner runner;

pom.xml

@@ -638,6 +638,16 @@
                 <artifactId>RoaringBitmap</artifactId>
                 <version>0.5.18</version>
             </dependency>
+            <dependency>
+                <groupId>org.ow2.asm</groupId>
+                <artifactId>asm</artifactId>
+                <version>5.2</version>
+            </dependency>
+            <dependency>
+                <groupId>org.ow2.asm</groupId>
+                <artifactId>asm-commons</artifactId>
+                <version>5.2</version>
+            </dependency>
             <dependency>
                 <groupId>org.apache.calcite</groupId>
                 <artifactId>calcite-core</artifactId>
@@ -815,10 +825,11 @@
                                 <version>1.0</version>
                             </signature>
                             <ignores>
-                                <!-- Some of our code uses DirectBuffer & Cleaner directly, which are not part of
+                                <!-- Some of our code uses sun.* classes directly, which are not part of
                                      the JDK signature (although they are there anyway). -->
                                 <ignore>sun.nio.ch.DirectBuffer</ignore>
                                 <ignore>sun.misc.Cleaner</ignore>
+                                <ignore>sun.misc.Unsafe</ignore>
                             </ignores>
                         </configuration>
                     </execution>

processing/pom.xml

@@ -93,6 +93,14 @@
             <groupId>commons-lang</groupId>
             <artifactId>commons-lang</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm-commons</artifactId>
+        </dependency>
 
         <!-- Tests -->
         <dependency>

processing/src/main/java/io/druid/query/BaseQuery.java

@@ -97,6 +97,13 @@ public abstract class BaseQuery<T extends Comparable<T>> implements Query<T>
     }
   }
 
+  public static void checkInterrupted()
+  {
+    if (Thread.interrupted()) {
+      throw new QueryInterruptedException(new InterruptedException());
+    }
+  }
+
   public static final String QUERYID = "queryId";
   private final DataSource dataSource;
   private final boolean descending;

processing/src/main/java/io/druid/query/aggregation/Aggregators.java

@@ -1,112 +0,0 @@
-/*
- * Licensed to Metamarkets Group Inc. (Metamarkets) under one
- * or more contributor license agreements. See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership. Metamarkets licenses this file
- * to you under the Apache License, Version 2.0 (the
- * "License"); you may not use this file except in compliance
- * with the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing,
- * software distributed under the License is distributed on an
- * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
- * KIND, either express or implied. See the License for the
- * specific language governing permissions and limitations
- * under the License.
- */
-
-package io.druid.query.aggregation;
-
-import java.nio.ByteBuffer;
-
-/**
- */
-public class Aggregators
-{
-  public static Aggregator noopAggregator()
-  {
-    return new Aggregator()
-    {
-      @Override
-      public void aggregate()
-      {
-
-      }
-
-      @Override
-      public void reset()
-      {
-
-      }
-
-      @Override
-      public Object get()
-      {
-        return null;
-      }
-
-      @Override
-      public float getFloat()
-      {
-        return 0;
-      }
-
-      @Override
-      public void close()
-      {
-
-      }
-
-      @Override
-      public long getLong()
-      {
-        return 0;
-      }
-    };
-  }
-
-  public static BufferAggregator noopBufferAggregator()
-  {
-    return new BufferAggregator()
-    {
-      @Override
-      public void init(ByteBuffer buf, int position)
-      {
-
-      }
-
-      @Override
-      public void aggregate(ByteBuffer buf, int position)
-      {
-
-      }
-
-      @Override
-      public Object get(ByteBuffer buf, int position)
-      {
-        return null;
-      }
-
-      @Override
-      public float getFloat(ByteBuffer buf, int position)
-      {
-        return 0;
-      }
-
-
-      @Override
-      public long getLong(ByteBuffer buf, int position)
-      {
-        return 0L;
-      }
-
-      @Override
-      public void close()
-      {
-
-      }
-    };
-  }
-}

processing/src/main/java/io/druid/query/aggregation/BufferAggregator.java

@@ -19,6 +19,10 @@
 
 package io.druid.query.aggregation;
 
+import io.druid.query.monomorphicprocessing.CalledFromHotLoop;
+import io.druid.query.monomorphicprocessing.HotLoopCallee;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+
 import java.nio.ByteBuffer;
 
 /**
@@ -29,7 +33,7 @@ import java.nio.ByteBuffer;
  * Thus, an Aggregator can be thought of as a closure over some other thing that is stateful and changes between calls
  * to aggregate(...).
  */
-public interface BufferAggregator
+public interface BufferAggregator extends HotLoopCallee
 {
   /**
    * Initializes the buffer location
@@ -44,6 +48,7 @@ public interface BufferAggregator
    * @param buf byte buffer to initialize
    * @param position offset within the byte buffer for initialization
    */
+  @CalledFromHotLoop
   void init(ByteBuffer buf, int position);
 
   /**
@@ -57,6 +62,7 @@ public interface BufferAggregator
    * @param buf byte buffer storing the byte array representation of the aggregate
    * @param position offset within the byte buffer at which the current aggregate value is stored
    */
+  @CalledFromHotLoop
   void aggregate(ByteBuffer buf, int position);
 
   /**
@@ -110,4 +116,14 @@ public interface BufferAggregator
    * Release any resources used by the aggregator
    */
   void close();
+
+  /**
+   * {@inheritDoc}
+   *
+   * <p>The default implementation inspects nothing. Classes that implement {@code BufferAggregator} are encouraged to
+   * override this method, following the specification of {@link HotLoopCallee#inspectRuntimeShape}.
+   */
+  default void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+  }
 }

processing/src/main/java/io/druid/query/aggregation/CountBufferAggregator.java

@@ -19,6 +19,8 @@
 
 package io.druid.query.aggregation;
 
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+
 import java.nio.ByteBuffer;
 
 /**
@@ -62,4 +64,9 @@ public class CountBufferAggregator implements BufferAggregator
   {
     // no resources to cleanup
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+  }
 }

processing/src/main/java/io/druid/query/aggregation/DoubleBufferAggregator.java

@@ -0,0 +1,65 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.aggregation;
+
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+import io.druid.segment.FloatColumnSelector;
+
+import java.nio.ByteBuffer;
+
+public abstract class DoubleBufferAggregator implements BufferAggregator
+{
+  protected final FloatColumnSelector selector;
+
+  DoubleBufferAggregator(FloatColumnSelector selector)
+  {
+    this.selector = selector;
+  }
+
+  @Override
+  public Object get(ByteBuffer buf, int position)
+  {
+    return buf.getDouble(position);
+  }
+
+  @Override
+  public float getFloat(ByteBuffer buf, int position)
+  {
+    return (float) buf.getDouble(position);
+  }
+
+  @Override
+  public long getLong(ByteBuffer buf, int position)
+  {
+    return (long) buf.getDouble(position);
+  }
+
+  @Override
+  public void close()
+  {
+    // no resources to cleanup
+  }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+  }
+}

processing/src/main/java/io/druid/query/aggregation/DoubleMaxBufferAggregator.java

@@ -25,13 +25,12 @@ import java.nio.ByteBuffer;
 
 /**
  */
-public class DoubleMaxBufferAggregator implements BufferAggregator
+public class DoubleMaxBufferAggregator extends DoubleBufferAggregator
 {
-  private final FloatColumnSelector selector;
 
-  public DoubleMaxBufferAggregator(FloatColumnSelector selector)
+  DoubleMaxBufferAggregator(FloatColumnSelector selector)
   {
-    this.selector = selector;
+    super(selector);
   }
 
   @Override
@@ -45,28 +44,4 @@ public class DoubleMaxBufferAggregator implements BufferAggregator
   {
     buf.putDouble(position, Math.max(buf.getDouble(position), (double) selector.get()));
   }
-
-  @Override
-  public Object get(ByteBuffer buf, int position)
-  {
-    return buf.getDouble(position);
-  }
-
-  @Override
-  public float getFloat(ByteBuffer buf, int position)
-  {
-    return (float) buf.getDouble(position);
-  }
-
-  @Override
-  public long getLong(ByteBuffer buf, int position)
-  {
-    return (long) buf.getDouble(position);
-  }
-
-  @Override
-  public void close()
-  {
-    // no resources to cleanup
-  }
 }

processing/src/main/java/io/druid/query/aggregation/DoubleMinBufferAggregator.java

@@ -25,13 +25,12 @@ import java.nio.ByteBuffer;
 
 /**
  */
-public class DoubleMinBufferAggregator implements BufferAggregator
+public class DoubleMinBufferAggregator extends DoubleBufferAggregator
 {
-  private final FloatColumnSelector selector;
 
-  public DoubleMinBufferAggregator(FloatColumnSelector selector)
+  DoubleMinBufferAggregator(FloatColumnSelector selector)
   {
-    this.selector = selector;
+    super(selector);
   }
 
   @Override
@@ -45,29 +44,4 @@ public class DoubleMinBufferAggregator implements BufferAggregator
   {
     buf.putDouble(position, Math.min(buf.getDouble(position), (double) selector.get()));
   }
-
-  @Override
-  public Object get(ByteBuffer buf, int position)
-  {
-    return buf.getDouble(position);
-  }
-
-  @Override
-  public float getFloat(ByteBuffer buf, int position)
-  {
-    return (float) buf.getDouble(position);
-  }
-
-
-  @Override
-  public long getLong(ByteBuffer buf, int position)
-  {
-    return  (long) buf.getDouble(position);
-  }
-
-  @Override
-  public void close()
-  {
-    // no resources to cleanup
-  }
 }

processing/src/main/java/io/druid/query/aggregation/DoubleSumBufferAggregator.java

@@ -25,15 +25,12 @@ import java.nio.ByteBuffer;
 
 /**
  */
-public class DoubleSumBufferAggregator implements BufferAggregator
+public class DoubleSumBufferAggregator extends DoubleBufferAggregator
 {
-  private final FloatColumnSelector selector;
 
-  public DoubleSumBufferAggregator(
-      FloatColumnSelector selector
-  )
+  DoubleSumBufferAggregator(FloatColumnSelector selector)
   {
-    this.selector = selector;
+    super(selector);
   }
 
   @Override
@@ -47,29 +44,4 @@ public class DoubleSumBufferAggregator implements BufferAggregator
   {
     buf.putDouble(position, buf.getDouble(position) + (double) selector.get());
   }
-
-  @Override
-  public Object get(ByteBuffer buf, int position)
-  {
-    return buf.getDouble(position);
-  }
-
-  @Override
-  public float getFloat(ByteBuffer buf, int position)
-  {
-    return (float) buf.getDouble(position);
-  }
-
-
-  @Override
-  public long getLong(ByteBuffer buf, int position)
-  {
-    return (long) buf.getDouble(position);
-  }
-
-  @Override
-  public void close()
-  {
-    // no resources to cleanup
-  }
 }

processing/src/main/java/io/druid/query/aggregation/FilteredBufferAggregator.java

@@ -20,6 +20,7 @@
 package io.druid.query.aggregation;
 
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 
 import java.nio.ByteBuffer;
 
@@ -71,4 +72,11 @@ public class FilteredBufferAggregator implements BufferAggregator
   {
     delegate.close();
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("matcher", matcher);
+    inspector.visit("delegate", delegate);
+  }
 }

processing/src/main/java/io/druid/query/aggregation/HistogramBufferAggregator.java

@@ -21,6 +21,7 @@ package io.druid.query.aggregation;
 
 import com.google.common.primitives.Floats;
 import com.google.common.primitives.Longs;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.FloatColumnSelector;
 
 import java.nio.ByteBuffer;
@@ -105,4 +106,10 @@ public class HistogramBufferAggregator implements BufferAggregator
   {
     // no resources to cleanup
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+  }
 }

processing/src/main/java/io/druid/query/aggregation/JavaScriptBufferAggregator.java

@@ -20,6 +20,7 @@
 package io.druid.query.aggregation;
 
 import com.google.common.collect.Lists;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ObjectColumnSelector;
 
 import java.nio.ByteBuffer;
@@ -74,4 +75,11 @@ public class JavaScriptBufferAggregator implements BufferAggregator
   public void close() {
     script.close();
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selectorList", selectorList);
+    inspector.visit("script", script);
+  }
 }

processing/src/main/java/io/druid/query/aggregation/LongBufferAggregator.java

@@ -0,0 +1,65 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.aggregation;
+
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+import io.druid.segment.LongColumnSelector;
+
+import java.nio.ByteBuffer;
+
+public abstract class LongBufferAggregator implements BufferAggregator
+{
+  protected final LongColumnSelector selector;
+
+  LongBufferAggregator(LongColumnSelector selector)
+  {
+    this.selector = selector;
+  }
+
+  @Override
+  public Object get(ByteBuffer buf, int position)
+  {
+    return buf.getLong(position);
+  }
+
+  @Override
+  public float getFloat(ByteBuffer buf, int position)
+  {
+    return (float) buf.getLong(position);
+  }
+
+  @Override
+  public long getLong(ByteBuffer buf, int position)
+  {
+    return buf.getLong(position);
+  }
+
+  @Override
+  public void close()
+  {
+    // no resources to cleanup
+  }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+  }
+}

processing/src/main/java/io/druid/query/aggregation/LongMaxBufferAggregator.java

@@ -25,13 +25,12 @@ import java.nio.ByteBuffer;
 
 /**
  */
-public class LongMaxBufferAggregator implements BufferAggregator
+public class LongMaxBufferAggregator extends LongBufferAggregator
 {
-  private final LongColumnSelector selector;
 
-  public LongMaxBufferAggregator(LongColumnSelector selector)
+  LongMaxBufferAggregator(LongColumnSelector selector)
   {
-    this.selector = selector;
+    super(selector);
   }
 
   @Override
@@ -45,28 +44,4 @@ public class LongMaxBufferAggregator implements BufferAggregator
   {
     buf.putLong(position, Math.max(buf.getLong(position), selector.get()));
   }
-
-  @Override
-  public Object get(ByteBuffer buf, int position)
-  {
-    return buf.getLong(position);
-  }
-
-  @Override
-  public float getFloat(ByteBuffer buf, int position)
-  {
-    return (float) buf.getLong(position);
-  }
-
-  @Override
-  public long getLong(ByteBuffer buf, int position)
-  {
-    return buf.getLong(position);
-  }
-
-  @Override
-  public void close()
-  {
-    // no resources to cleanup
-  }
 }

processing/src/main/java/io/druid/query/aggregation/LongMinBufferAggregator.java

@@ -25,13 +25,12 @@ import java.nio.ByteBuffer;
 
 /**
  */
-public class LongMinBufferAggregator implements BufferAggregator
+public class LongMinBufferAggregator extends LongBufferAggregator
 {
-  private final LongColumnSelector selector;
 
-  public LongMinBufferAggregator(LongColumnSelector selector)
+  LongMinBufferAggregator(LongColumnSelector selector)
   {
-    this.selector = selector;
+    super(selector);
   }
 
   @Override
@@ -45,29 +44,4 @@ public class LongMinBufferAggregator implements BufferAggregator
   {
     buf.putLong(position, Math.min(buf.getLong(position), selector.get()));
   }
-
-  @Override
-  public Object get(ByteBuffer buf, int position)
-  {
-    return buf.getLong(position);
-  }
-
-  @Override
-  public float getFloat(ByteBuffer buf, int position)
-  {
-    return (float) buf.getLong(position);
-  }
-
-
-  @Override
-  public long getLong(ByteBuffer buf, int position)
-  {
-    return buf.getLong(position);
-  }
-
-  @Override
-  public void close()
-  {
-    // no resources to cleanup
-  }
 }

processing/src/main/java/io/druid/query/aggregation/LongSumBufferAggregator.java

@@ -25,15 +25,12 @@ import java.nio.ByteBuffer;
 
 /**
  */
-public class LongSumBufferAggregator implements BufferAggregator
+public class LongSumBufferAggregator extends LongBufferAggregator
 {
-  private final LongColumnSelector selector;
 
-  public LongSumBufferAggregator(
-      LongColumnSelector selector
-  )
+  LongSumBufferAggregator(LongColumnSelector selector)
   {
-    this.selector = selector;
+    super(selector);
   }
 
   @Override
@@ -47,29 +44,4 @@ public class LongSumBufferAggregator implements BufferAggregator
   {
     buf.putLong(position, buf.getLong(position) + selector.get());
   }
-
-  @Override
-  public Object get(ByteBuffer buf, int position)
-  {
-    return buf.getLong(position);
-  }
-
-  @Override
-  public float getFloat(ByteBuffer buf, int position)
-  {
-    return (float) buf.getLong(position);
-  }
-
-
-  @Override
-  public long getLong(ByteBuffer buf, int position)
-  {
-    return buf.getLong(position);
-  }
-
-  @Override
-  public void close()
-  {
-    // no resources to cleanup
-  }
 }

processing/src/main/java/io/druid/query/aggregation/NoopAggregator.java

@@ -17,47 +17,51 @@
  * under the License.
  */
 
-package io.druid.segment;
+package io.druid.query.aggregation;
 
-import io.druid.segment.data.IndexedInts;
-import io.druid.segment.data.Offset;
-
-/**
-*/
-class IndexedIntsOffset implements Offset
+public final class NoopAggregator implements Aggregator
 {
-  int currRow;
-  private final IndexedInts invertedIndex;
+  private static final NoopAggregator INSTANCE = new NoopAggregator();
 
-  public IndexedIntsOffset(IndexedInts invertedIndex)
+  public static NoopAggregator instance()
+  {
+    return INSTANCE;
+  }
+
+  private NoopAggregator()
   {
-    this.invertedIndex = invertedIndex;
-    currRow = 0;
   }
 
   @Override
-  public void increment()
+  public void aggregate()
   {
-    ++currRow;
   }
 
   @Override
-  public boolean withinBounds()
+  public void reset()
   {
-    return currRow < invertedIndex.size();
   }
 
   @Override
-  public Offset clone()
+  public Object get()
   {
-    final IndexedIntsOffset retVal = new IndexedIntsOffset(invertedIndex);
-    retVal.currRow = currRow;
-    return retVal;
+    return null;
   }
 
   @Override
-  public int getOffset()
+  public float getFloat()
   {
-    return invertedIndex.get(currRow);
+    return 0;
+  }
+
+  @Override
+  public void close()
+  {
+  }
+
+  @Override
+  public long getLong()
+  {
+    return 0;
   }
 }

processing/src/main/java/io/druid/query/aggregation/NoopBufferAggregator.java

@@ -0,0 +1,77 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.aggregation;
+
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+
+import java.nio.ByteBuffer;
+
+public final class NoopBufferAggregator implements BufferAggregator
+{
+  private static final NoopBufferAggregator INSTANCE = new NoopBufferAggregator();
+
+  public static NoopBufferAggregator instance()
+  {
+    return INSTANCE;
+  }
+
+  private NoopBufferAggregator()
+  {
+  }
+
+  @Override
+  public void init(ByteBuffer buf, int position)
+  {
+  }
+
+  @Override
+  public void aggregate(ByteBuffer buf, int position)
+  {
+  }
+
+  @Override
+  public Object get(ByteBuffer buf, int position)
+  {
+    return null;
+  }
+
+  @Override
+  public float getFloat(ByteBuffer buf, int position)
+  {
+    return 0;
+  }
+
+
+  @Override
+  public long getLong(ByteBuffer buf, int position)
+  {
+    return 0L;
+  }
+
+  @Override
+  public void close()
+  {
+  }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+  }
+}

processing/src/main/java/io/druid/query/aggregation/cardinality/CardinalityAggregator.java

@@ -19,12 +19,13 @@
 
 package io.druid.query.aggregation.cardinality;
 
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.hash.HashFunction;
 import com.google.common.hash.Hasher;
 import com.google.common.hash.Hashing;
 import io.druid.hll.HyperLogLogCollector;
-import io.druid.query.aggregation.Aggregator;
 import io.druid.query.ColumnSelectorPlus;
+import io.druid.query.aggregation.Aggregator;
 import io.druid.query.aggregation.cardinality.types.CardinalityAggregatorColumnSelectorStrategy;
 
 import java.util.List;
@@ -32,48 +33,59 @@ import java.util.List;
 public class CardinalityAggregator implements Aggregator
 {
   private final String name;
-  private final List<ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>> selectorPlusList;
+  private final ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>[] selectorPluses;
   private final boolean byRow;
 
   public static final HashFunction hashFn = Hashing.murmur3_128();
 
-  protected static void hashRow(
-      List<ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>> selectorPlusList,
+  static void hashRow(
+      ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>[] selectorPluses,
       HyperLogLogCollector collector
   )
   {
     final Hasher hasher = hashFn.newHasher();
-    for (int k = 0; k < selectorPlusList.size(); ++k) {
+    for (int k = 0; k < selectorPluses.length; ++k) {
       if (k != 0) {
         hasher.putByte((byte) 0);
       }
 
-      ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy> selectorPlus = selectorPlusList.get(k);
+      ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy> selectorPlus = selectorPluses[k];
       selectorPlus.getColumnSelectorStrategy().hashRow(selectorPlus.getSelector(), hasher);
     }
     collector.add(hasher.hash().asBytes());
   }
 
-  protected static void hashValues(
-      List<ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>> selectorPlusList,
+  static void hashValues(
+      ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>[] selectorPluses,
       HyperLogLogCollector collector
   )
   {
-    for (final ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy> selectorPlus : selectorPlusList) {
+    for (final ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy> selectorPlus : selectorPluses) {
       selectorPlus.getColumnSelectorStrategy().hashValues(selectorPlus.getSelector(), collector);
     }
   }
 
   private HyperLogLogCollector collector;
 
-  public CardinalityAggregator(
+  @VisibleForTesting
+  @SuppressWarnings("unchecked")
+  CardinalityAggregator(
       String name,
       List<ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>> selectorPlusList,
       boolean byRow
   )
+  {
+    this(name, selectorPlusList.toArray(new ColumnSelectorPlus[] {}), byRow);
+  }
+
+  CardinalityAggregator(
+      String name,
+      ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>[] selectorPluses,
+      boolean byRow
+  )
   {
     this.name = name;
-    this.selectorPlusList = selectorPlusList;
+    this.selectorPluses = selectorPluses;
     this.collector = HyperLogLogCollector.makeLatestCollector();
     this.byRow = byRow;
   }
@@ -82,9 +94,9 @@ public class CardinalityAggregator implements Aggregator
   public void aggregate()
   {
     if (byRow) {
-      hashRow(selectorPlusList, collector);
+      hashRow(selectorPluses, collector);
     } else {
-      hashValues(selectorPlusList, collector);
+      hashValues(selectorPluses, collector);
     }
   }
 
@@ -115,7 +127,7 @@ public class CardinalityAggregator implements Aggregator
   @Override
   public Aggregator clone()
   {
-    return new CardinalityAggregator(name, selectorPlusList, byRow);
+    return new CardinalityAggregator(name, selectorPluses, byRow);
   }
 
   @Override

processing/src/main/java/io/druid/query/aggregation/cardinality/CardinalityAggregatorFactory.java

@@ -31,8 +31,9 @@ import io.druid.query.ColumnSelectorPlus;
 import io.druid.query.aggregation.Aggregator;
 import io.druid.query.aggregation.AggregatorFactory;
 import io.druid.query.aggregation.AggregatorFactoryNotMergeableException;
-import io.druid.query.aggregation.Aggregators;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.aggregation.NoopAggregator;
+import io.druid.query.aggregation.NoopBufferAggregator;
 import io.druid.query.aggregation.cardinality.types.CardinalityAggregatorColumnSelectorStrategy;
 import io.druid.query.aggregation.cardinality.types.CardinalityAggregatorColumnSelectorStrategyFactory;
 import io.druid.query.aggregation.hyperloglog.HyperUniquesAggregatorFactory;
@@ -44,7 +45,6 @@ import org.apache.commons.codec.binary.Base64;
 
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
@@ -137,36 +137,34 @@ public class CardinalityAggregatorFactory extends AggregatorFactory
   @Override
   public Aggregator factorize(final ColumnSelectorFactory columnFactory)
   {
-    List<ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>> selectorPlusList =
-        Arrays.asList(DimensionHandlerUtils.createColumnSelectorPluses(
+    ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>[] selectorPluses =
+        DimensionHandlerUtils.createColumnSelectorPluses(
             STRATEGY_FACTORY,
             fields,
             columnFactory
-        ));
+        );
 
-    if (selectorPlusList.isEmpty()) {
-      return Aggregators.noopAggregator();
+    if (selectorPluses.length == 0) {
+      return NoopAggregator.instance();
     }
-
-    return new CardinalityAggregator(name, selectorPlusList, byRow);
+    return new CardinalityAggregator(name, selectorPluses, byRow);
   }
 
 
   @Override
   public BufferAggregator factorizeBuffered(ColumnSelectorFactory columnFactory)
   {
-    List<ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>> selectorPlusList =
-        Arrays.asList(DimensionHandlerUtils.createColumnSelectorPluses(
+    ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>[] selectorPluses =
+        DimensionHandlerUtils.createColumnSelectorPluses(
             STRATEGY_FACTORY,
             fields,
             columnFactory
-        ));
+        );
 
-    if (selectorPlusList.isEmpty()) {
-      return Aggregators.noopBufferAggregator();
+    if (selectorPluses.length == 0) {
+      return NoopBufferAggregator.instance();
     }
-
-    return new CardinalityBufferAggregator(selectorPlusList, byRow);
+    return new CardinalityBufferAggregator(selectorPluses, byRow);
   }
 
   @Override

processing/src/main/java/io/druid/query/aggregation/cardinality/CardinalityBufferAggregator.java

@@ -20,26 +20,26 @@
 package io.druid.query.aggregation.cardinality;
 
 import io.druid.hll.HyperLogLogCollector;
-import io.druid.query.aggregation.BufferAggregator;
 import io.druid.query.ColumnSelectorPlus;
+import io.druid.query.aggregation.BufferAggregator;
 import io.druid.query.aggregation.cardinality.types.CardinalityAggregatorColumnSelectorStrategy;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 
 import java.nio.ByteBuffer;
-import java.util.List;
 
 public class CardinalityBufferAggregator implements BufferAggregator
 {
-  private final List<ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>> selectorPlusList;
+  private final ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>[] selectorPluses;
   private final boolean byRow;
 
   private static final byte[] EMPTY_BYTES = HyperLogLogCollector.makeEmptyVersionedByteArray();
 
-  public CardinalityBufferAggregator(
-      List<ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>> selectorPlusList,
+  CardinalityBufferAggregator(
+      ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>[] selectorPluses,
       boolean byRow
   )
   {
-    this.selectorPlusList = selectorPlusList;
+    this.selectorPluses = selectorPluses;
     this.byRow = byRow;
   }
 
@@ -63,9 +63,9 @@ public class CardinalityBufferAggregator implements BufferAggregator
     try {
       final HyperLogLogCollector collector = HyperLogLogCollector.makeCollector(buf);
       if (byRow) {
-        CardinalityAggregator.hashRow(selectorPlusList, collector);
+        CardinalityAggregator.hashRow(selectorPluses, collector);
       } else {
-        CardinalityAggregator.hashValues(selectorPlusList, collector);
+        CardinalityAggregator.hashValues(selectorPluses, collector);
       }
     }
     finally {
@@ -102,4 +102,10 @@ public class CardinalityBufferAggregator implements BufferAggregator
   {
     // no resources to cleanup
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selectorPluses", selectorPluses);
+  }
 }

processing/src/main/java/io/druid/query/aggregation/first/DoubleFirstAggregatorFactory.java

@@ -30,6 +30,7 @@ import io.druid.query.aggregation.Aggregator;
 import io.druid.query.aggregation.AggregatorFactory;
 import io.druid.query.aggregation.AggregatorFactoryNotMergeableException;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ColumnSelectorFactory;
 import io.druid.segment.ObjectColumnSelector;
 import io.druid.segment.column.Column;
@@ -148,6 +149,12 @@ public class DoubleFirstAggregatorFactory extends AggregatorFactory
               buf.putDouble(position + Longs.BYTES, pair.rhs);
             }
           }
+
+          @Override
+          public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+          {
+            inspector.visit("selector", selector);
+          }
         };
       }
     };

processing/src/main/java/io/druid/query/aggregation/first/DoubleFirstBufferAggregator.java

@@ -22,6 +22,7 @@ package io.druid.query.aggregation.first;
 import com.google.common.primitives.Longs;
 import io.druid.collections.SerializablePair;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.FloatColumnSelector;
 import io.druid.segment.LongColumnSelector;
 
@@ -79,4 +80,11 @@ public class DoubleFirstBufferAggregator implements BufferAggregator
   {
     // no resources to cleanup
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("timeSelector", timeSelector);
+    inspector.visit("valueSelector", valueSelector);
+  }
 }

processing/src/main/java/io/druid/query/aggregation/first/LongFirstAggregatorFactory.java

@@ -29,6 +29,7 @@ import io.druid.query.aggregation.Aggregator;
 import io.druid.query.aggregation.AggregatorFactory;
 import io.druid.query.aggregation.AggregatorFactoryNotMergeableException;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ColumnSelectorFactory;
 import io.druid.segment.ObjectColumnSelector;
 import io.druid.segment.column.Column;
@@ -138,6 +139,12 @@ public class LongFirstAggregatorFactory extends AggregatorFactory
               buf.putLong(position + Longs.BYTES, pair.rhs);
             }
           }
+
+          @Override
+          public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+          {
+            inspector.visit("selector", selector);
+          }
         };
       }
     };

processing/src/main/java/io/druid/query/aggregation/first/LongFirstBufferAggregator.java

@@ -22,6 +22,7 @@ package io.druid.query.aggregation.first;
 import com.google.common.primitives.Longs;
 import io.druid.collections.SerializablePair;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.LongColumnSelector;
 
 import java.nio.ByteBuffer;
@@ -78,4 +79,11 @@ public class LongFirstBufferAggregator implements BufferAggregator
   {
     // no resources to cleanup
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("timeSelector", timeSelector);
+    inspector.visit("valueSelector", valueSelector);
+  }
 }

processing/src/main/java/io/druid/query/aggregation/hyperloglog/HyperUniquesAggregatorFactory.java

@@ -28,8 +28,9 @@ import io.druid.java.util.common.StringUtils;
 import io.druid.query.aggregation.Aggregator;
 import io.druid.query.aggregation.AggregatorFactory;
 import io.druid.query.aggregation.AggregatorFactoryNotMergeableException;
-import io.druid.query.aggregation.Aggregators;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.aggregation.NoopAggregator;
+import io.druid.query.aggregation.NoopBufferAggregator;
 import io.druid.segment.ColumnSelectorFactory;
 import io.druid.segment.ObjectColumnSelector;
 import org.apache.commons.codec.binary.Base64;
@@ -85,7 +86,7 @@ public class HyperUniquesAggregatorFactory extends AggregatorFactory
     ObjectColumnSelector selector = metricFactory.makeObjectColumnSelector(fieldName);
 
     if (selector == null) {
-      return Aggregators.noopAggregator();
+      return NoopAggregator.instance();
     }
 
     final Class classOfObject = selector.classOfObject();
@@ -104,7 +105,7 @@ public class HyperUniquesAggregatorFactory extends AggregatorFactory
     ObjectColumnSelector selector = metricFactory.makeObjectColumnSelector(fieldName);
 
     if (selector == null) {
-      return Aggregators.noopBufferAggregator();
+      return NoopBufferAggregator.instance();
     }
 
     final Class classOfObject = selector.classOfObject();

processing/src/main/java/io/druid/query/aggregation/hyperloglog/HyperUniquesBufferAggregator.java

@@ -21,6 +21,7 @@ package io.druid.query.aggregation.hyperloglog;
 
 import io.druid.hll.HyperLogLogCollector;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ObjectColumnSelector;
 
 import java.nio.ByteBuffer;
@@ -102,4 +103,10 @@ public class HyperUniquesBufferAggregator implements BufferAggregator
   {
     // no resources to cleanup
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+  }
 }

processing/src/main/java/io/druid/query/aggregation/last/DoubleLastAggregatorFactory.java

@@ -32,6 +32,7 @@ import io.druid.query.aggregation.AggregatorFactoryNotMergeableException;
 import io.druid.query.aggregation.BufferAggregator;
 import io.druid.query.aggregation.first.DoubleFirstAggregatorFactory;
 import io.druid.query.aggregation.first.LongFirstAggregatorFactory;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ColumnSelectorFactory;
 import io.druid.segment.ObjectColumnSelector;
 import io.druid.segment.column.Column;
@@ -131,6 +132,12 @@ public class DoubleLastAggregatorFactory extends AggregatorFactory
               buf.putDouble(position + Longs.BYTES, pair.rhs);
             }
           }
+
+          @Override
+          public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+          {
+            inspector.visit("selector", selector);
+          }
         };
       }
     };

processing/src/main/java/io/druid/query/aggregation/last/DoubleLastBufferAggregator.java

@@ -22,6 +22,7 @@ package io.druid.query.aggregation.last;
 import com.google.common.primitives.Longs;
 import io.druid.collections.SerializablePair;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.FloatColumnSelector;
 import io.druid.segment.LongColumnSelector;
 
@@ -79,4 +80,11 @@ public class DoubleLastBufferAggregator implements BufferAggregator
   {
     // no resources to cleanup
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("timeSelector", timeSelector);
+    inspector.visit("valueSelector", valueSelector);
+  }
 }

processing/src/main/java/io/druid/query/aggregation/last/LongLastAggregatorFactory.java

@@ -31,6 +31,7 @@ import io.druid.query.aggregation.AggregatorFactoryNotMergeableException;
 import io.druid.query.aggregation.BufferAggregator;
 import io.druid.query.aggregation.first.DoubleFirstAggregatorFactory;
 import io.druid.query.aggregation.first.LongFirstAggregatorFactory;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ColumnSelectorFactory;
 import io.druid.segment.ObjectColumnSelector;
 import io.druid.segment.column.Column;
@@ -131,6 +132,12 @@ public class LongLastAggregatorFactory extends AggregatorFactory
               buf.putLong(position + Longs.BYTES, pair.rhs);
             }
           }
+
+          @Override
+          public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+          {
+            inspector.visit("selector", selector);
+          }
         };
       }
     };

processing/src/main/java/io/druid/query/aggregation/last/LongLastBufferAggregator.java

@@ -22,6 +22,7 @@ package io.druid.query.aggregation.last;
 import com.google.common.primitives.Longs;
 import io.druid.collections.SerializablePair;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.LongColumnSelector;
 
 import java.nio.ByteBuffer;
@@ -78,4 +79,11 @@ public class LongLastBufferAggregator implements BufferAggregator
   {
     // no resources to cleanup
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("timeSelector", timeSelector);
+    inspector.visit("valueSelector", valueSelector);
+  }
 }

processing/src/main/java/io/druid/query/dimension/ForwardingFilteredDimensionSelector.java

@@ -24,6 +24,7 @@ import com.google.common.base.Predicate;
 import com.google.common.base.Predicates;
 import io.druid.java.util.common.IAE;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.DimensionSelector;
 import io.druid.segment.DimensionSelectorUtils;
 import io.druid.segment.IdLookup;
@@ -173,4 +174,11 @@ final class ForwardingFilteredDimensionSelector implements DimensionSelector, Id
   {
     return forwardMapping.get(baseIdLookup.lookupId(name));
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+    inspector.visit("forwardMapping", forwardMapping);
+  }
 }

processing/src/main/java/io/druid/query/dimension/PredicateFilteredDimensionSelector.java

@@ -21,6 +21,7 @@ package io.druid.query.dimension;
 
 import com.google.common.base.Predicate;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.DimensionSelector;
 import io.druid.segment.IdLookup;
 import io.druid.segment.data.ArrayBasedIndexedInts;
@@ -132,4 +133,11 @@ final class PredicateFilteredDimensionSelector implements DimensionSelector
   {
     return selector.idLookup();
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+    inspector.visit("predicate", predicate);
+  }
 }

processing/src/main/java/io/druid/query/groupby/RowBasedColumnSelectorFactory.java

@@ -27,6 +27,7 @@ import io.druid.data.input.Row;
 import io.druid.query.dimension.DimensionSpec;
 import io.druid.query.extraction.ExtractionFn;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ColumnSelectorFactory;
 import io.druid.segment.DimensionSelector;
 import io.druid.segment.FloatColumnSelector;
@@ -164,6 +165,13 @@ public class RowBasedColumnSelectorFactory implements ColumnSelectorFactory
         {
           return null;
         }
+
+        @Override
+        public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+        {
+          inspector.visit("row", row);
+          inspector.visit("extractionFn", extractionFn);
+        }
       };
     } else {
       return new DimensionSelector()
@@ -289,6 +297,13 @@ public class RowBasedColumnSelectorFactory implements ColumnSelectorFactory
         {
           return null;
         }
+
+        @Override
+        public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+        {
+          inspector.visit("row", row);
+          inspector.visit("extractionFn", extractionFn);
+        }
       };
     }
   }
@@ -296,17 +311,26 @@ public class RowBasedColumnSelectorFactory implements ColumnSelectorFactory
   @Override
   public FloatColumnSelector makeFloatColumnSelector(final String columnName)
   {
+    abstract class RowBasedFloatColumnSelector implements FloatColumnSelector
+    {
+      @Override
+      public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+      {
+        inspector.visit("row", row);
+      }
+    }
     if (columnName.equals(Column.TIME_COLUMN_NAME)) {
-      return new FloatColumnSelector()
+      class TimeFloatColumnSelector extends RowBasedFloatColumnSelector
       {
         @Override
         public float get()
         {
           return (float) row.get().getTimestampFromEpoch();
         }
-      };
+      }
+      return new TimeFloatColumnSelector();
     } else {
-      return new FloatColumnSelector()
+      return new RowBasedFloatColumnSelector()
       {
         @Override
         public float get()
@@ -320,17 +344,26 @@ public class RowBasedColumnSelectorFactory implements ColumnSelectorFactory
   @Override
   public LongColumnSelector makeLongColumnSelector(final String columnName)
   {
+    abstract class RowBasedLongColumnSelector implements LongColumnSelector
+    {
+      @Override
+      public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+      {
+        inspector.visit("row", row);
+      }
+    }
     if (columnName.equals(Column.TIME_COLUMN_NAME)) {
-      return new LongColumnSelector()
+      class TimeLongColumnSelector extends RowBasedLongColumnSelector
       {
         @Override
         public long get()
         {
           return row.get().getTimestampFromEpoch();
         }
-      };
+      }
+      return new TimeLongColumnSelector();
     } else {
-      return new LongColumnSelector()
+      return new RowBasedLongColumnSelector()
       {
         @Override
         public long get()

processing/src/main/java/io/druid/query/groupby/epinephelinae/RowBasedGrouperHelper.java

@@ -38,7 +38,7 @@ import io.druid.java.util.common.IAE;
 import io.druid.java.util.common.Pair;
 import io.druid.java.util.common.granularity.AllGranularity;
 import io.druid.java.util.common.guava.Accumulator;
-import io.druid.query.QueryInterruptedException;
+import io.druid.query.BaseQuery;
 import io.druid.query.aggregation.AggregatorFactory;
 import io.druid.query.dimension.DimensionSpec;
 import io.druid.query.groupby.GroupByQuery;
@@ -152,9 +152,7 @@ public class RowBasedGrouperHelper
           final Row row
       )
       {
-        if (Thread.interrupted()) {
-          throw new QueryInterruptedException(new InterruptedException());
-        }
+        BaseQuery.checkInterrupted();
 
         if (theGrouper == null) {
           // Pass-through null returns without doing more work.

processing/src/main/java/io/druid/query/groupby/epinephelinae/SpillingGrouper.java

@@ -28,7 +28,7 @@ import com.google.common.base.Throwables;
 import com.google.common.collect.Iterators;
 import com.google.common.collect.Lists;
 import io.druid.java.util.common.guava.CloseQuietly;
-import io.druid.query.QueryInterruptedException;
+import io.druid.query.BaseQuery;
 import io.druid.query.aggregation.AggregatorFactory;
 import io.druid.segment.ColumnSelectorFactory;
 import net.jpountz.lz4.LZ4BlockInputStream;
@@ -200,9 +200,7 @@ public class SpillingGrouper<KeyType> implements Grouper<KeyType>
       outFile = out.getFile();
       final Iterator<Entry<KeyType>> it = grouper.iterator(true);
       while (it.hasNext()) {
-        if (Thread.interrupted()) {
-          throw new QueryInterruptedException(new InterruptedException());
-        }
+        BaseQuery.checkInterrupted();
 
         jsonGenerator.writeObject(it.next());
       }

processing/src/main/java/io/druid/query/monomorphicprocessing/CalledFromHotLoop.java

@@ -0,0 +1,43 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.monomorphicprocessing;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation for methods, which are called from hot loops during query processing. Those methods and their downstream
+ * callees should be optimized as much as possible.
+ *
+ * <p>Currently CalledFromHotLoop is a source-level annotation, used only for documentation.
+ *
+ * @see HotLoopCallee
+ */
+@Documented
+@Inherited
+@Retention(RetentionPolicy.SOURCE)
+@Target(ElementType.METHOD)
+public @interface CalledFromHotLoop
+{
+}

processing/src/main/java/io/druid/query/monomorphicprocessing/HotLoopCallee.java

@@ -0,0 +1,43 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.monomorphicprocessing;
+
+/**
+ * Marker interface for abstractions, which are called from hot loops during query processing. Some of the methods of
+ * interfaces extending HotLoopCallee should be annotated with {@link CalledFromHotLoop}.
+ */
+public interface HotLoopCallee
+{
+  /**
+   * Implementations of this method should call {@code inspector.visit()} with all fields of this class, which meet two
+   * conditions:
+   *  1. They are used in methods of this class, annotated with {@link CalledFromHotLoop}
+   *  2. They are either:
+   *     a. Nullable objects
+   *     b. Instances of HotLoopCallee
+   *     c. Objects, which don't always have a specific class in runtime. For example, a field of type {@link
+   *        java.util.Set} could be {@link java.util.HashSet} or {@link java.util.TreeSet} in runtime, depending on how
+   *        this instance (the instance on which inspectRuntimeShape() is called) is configured.
+   *     d. ByteBuffer or similar objects, where byte order matters
+   *     e. boolean flags, affecting branch taking
+   *     f. Arrays of objects, meeting conditions any of conditions a-e.
+   */
+  void inspectRuntimeShape(RuntimeShapeInspector inspector);
+}

processing/src/main/java/io/druid/query/monomorphicprocessing/RuntimeShapeInspector.java

@@ -0,0 +1,44 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.monomorphicprocessing;
+
+import javax.annotation.Nullable;
+
+/**
+ * @see HotLoopCallee#inspectRuntimeShape(RuntimeShapeInspector)
+ */
+public interface RuntimeShapeInspector
+{
+  void visit(String fieldName, @Nullable HotLoopCallee value);
+
+  void visit(String fieldName, @Nullable Object value);
+
+  <T> void visit(String fieldName, T[] values);
+
+  void visit(String flagName, boolean flagValue);
+
+  /**
+   * To be called from {@link HotLoopCallee#inspectRuntimeShape(RuntimeShapeInspector)} with something, that is
+   * important to ensure monomorphism and predictable branch taking in hot loops, but doesn't apply to other visit()
+   * methods in RuntimeShapeInspector. For example, {@link io.druid.segment.BitmapOffset#inspectRuntimeShape} reports
+   * bitmap population via this method, to ensure predictable branch taking inside Bitmap's iterators.
+   */
+  void visit(String key, String runtimeShape);
+}

processing/src/main/java/io/druid/query/monomorphicprocessing/SpecializationService.java

@@ -0,0 +1,401 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.monomorphicprocessing;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.io.ByteStreams;
+import io.druid.concurrent.Execs;
+import io.druid.java.util.common.logger.Logger;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.commons.ClassRemapper;
+import org.objectweb.asm.commons.SimpleRemapper;
+import sun.misc.Unsafe;
+
+import javax.annotation.Nullable;
+import java.io.IOException;
+import java.io.InputStream;
+import java.lang.reflect.Field;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * Manages class specialization during query processing.
+ * Usage:
+ *
+ * String runtimeShape = stringRuntimeShape.of(bufferAggregator);
+ * SpecializationState<ProcessingAlgorithm> specializationState = SpecializationService.getSpecializationState(
+ *   ProcessingAlgorithmImpl.class,
+ *   runtimeShape
+ * );
+ * ProcessingAlgorithm algorithm = specializationState.getSpecializedOrDefault(new ProcessingAlgorithmImpl());
+ * long loopIterations = new ProcessingAlgorithmImpl().run(bufferAggregator, ...);
+ * specializationState.accountLoopIterations(loopIterations);
+ *
+ * ProcessingAlgorithmImpl.class, passed as prototypeClass to {@link #getSpecializationState} methods must have public
+ * no-arg constructor and must be stateless (no fields).
+ *
+ * @see SpecializationState
+ */
+public final class SpecializationService
+{
+  private static final Logger LOG = new Logger(SpecializationService.class);
+
+  private static final Unsafe UNSAFE;
+  static {
+    try {
+      Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
+      theUnsafe.setAccessible(true);
+      UNSAFE = (Unsafe) theUnsafe.get(null);
+    }
+    catch (Exception e) {
+      throw new RuntimeException("Cannot access Unsafe methods", e);
+    }
+  }
+
+  /**
+   * If true, specialization is not actually done, an instance of prototypeClass is used as a "specialized" instance.
+   * Useful for analysis of generated assembly with JITWatch (https://github.com/AdoptOpenJDK/jitwatch), because
+   * JITWatch shows only classes present in the loaded JAR (prototypeClass should be), not classes generated during
+   * runtime.
+   */
+  private static final boolean fakeSpecialize = Boolean.getBoolean("fakeSpecialize");
+
+  /**
+   * Number of loop iterations, accounted via {@link SpecializationState#accountLoopIterations(long)} in
+   * {@link WindowedLoopIterationCounter} during the last hour window, after which WindowedLoopIterationCounter decides
+   * to specialize class for the specific runtimeShape. The default value is chosen to be so that the specialized
+   * class will likely be compiled with C2 HotSpot compiler with the default values of *BackEdgeThreshold options.
+   */
+  private static final int triggerSpecializationIterationsThreshold =
+      Integer.getInteger("triggerSpecializationIterationsThreshold", 10_000);
+
+  /**
+   * The maximum number of specializations, that this service is allowed to make. It's not unlimited because each
+   * specialization takes some JVM memory (machine code cache, byte code, etc.)
+   */
+  private static final int maxSpecializations = Integer.getInteger("maxSpecializations", 1000);
+
+  private static final ExecutorService classSpecializationExecutor = Execs.singleThreaded("class-specialization-%d");
+
+  private static final AtomicLong specializedClassCounter = new AtomicLong();
+
+  private static final ClassValue<PerPrototypeClassState> perPrototypeClassState =
+      new ClassValue<PerPrototypeClassState>()
+      {
+        @Override
+        protected PerPrototypeClassState computeValue(Class<?> type)
+        {
+          return new PerPrototypeClassState<>(type);
+        }
+      };
+
+  /**
+   * @param <T> type of query processing algorithm
+   * @see SpecializationService class-level javadoc for details
+   */
+  public static <T> SpecializationState<T> getSpecializationState(
+      Class<? extends T> prototypeClass,
+      String runtimeShape
+  )
+  {
+    return getSpecializationState(prototypeClass, runtimeShape, ImmutableMap.<Class<?>, Class<?>>of());
+  }
+
+  /**
+   * @param classRemapping classes, that should be replaced in the bytecode of the given prototypeClass when specialized
+   * @see #getSpecializationState(Class, String)
+   */
+  @SuppressWarnings("unchecked")
+  public static <T> SpecializationState<T> getSpecializationState(
+      Class<? extends T> prototypeClass,
+      String runtimeShape,
+      ImmutableMap<Class<?>, Class<?>> classRemapping
+  )
+  {
+    return perPrototypeClassState.get(prototypeClass).getSpecializationState(runtimeShape, classRemapping);
+  }
+
+  static class PerPrototypeClassState<T>
+  {
+    private final Class<T> prototypeClass;
+    private final ConcurrentMap<SpecializationId, SpecializationState<T>> specializationStates =
+        new ConcurrentHashMap<>();
+    private final String prototypeClassBytecodeName;
+    private final String specializedClassNamePrefix;
+
+    private byte[] prototypeClassBytecode;
+
+    PerPrototypeClassState(Class<T> prototypeClass)
+    {
+      this.prototypeClass = prototypeClass;
+      String prototypeClassName = prototypeClass.getName();
+      prototypeClassBytecodeName = classBytecodeName(prototypeClassName);
+      specializedClassNamePrefix = prototypeClassName + "$Copy";
+    }
+
+    SpecializationState<T> getSpecializationState(String runtimeShape, ImmutableMap<Class<?>, Class<?>> classRemapping)
+    {
+      SpecializationId specializationId = new SpecializationId(runtimeShape, classRemapping);
+      SpecializationState<T> alreadyExistingState = specializationStates.get(specializationId);
+      if (alreadyExistingState != null) {
+        return alreadyExistingState;
+      }
+      return specializationStates.computeIfAbsent(specializationId, id -> new WindowedLoopIterationCounter<>(this, id));
+    }
+
+    T specialize(ImmutableMap<Class<?>, Class<?>> classRemapping)
+    {
+      String specializedClassName = specializedClassNamePrefix + specializedClassCounter.get();
+      ClassWriter specializedClassWriter = new ClassWriter(0);
+      SimpleRemapper remapper = new SimpleRemapper(createRemapping(classRemapping, specializedClassName));
+      ClassVisitor classTransformer = new ClassRemapper(specializedClassWriter, remapper);
+      try {
+        ClassReader prototypeClassReader = new ClassReader(getPrototypeClassBytecode());
+        prototypeClassReader.accept(classTransformer, 0);
+        byte[] specializedClassBytecode = specializedClassWriter.toByteArray();
+        Class<T> specializedClass = defineClass(specializedClassName, specializedClassBytecode);
+        specializedClassCounter.incrementAndGet();
+        return specializedClass.newInstance();
+      }
+      catch (InstantiationException | IllegalAccessException | IOException e) {
+        throw new RuntimeException(e);
+      }
+    }
+
+    private HashMap<String, String> createRemapping(
+        ImmutableMap<Class<?>, Class<?>> classRemapping,
+        String specializedClassName
+    )
+    {
+      HashMap<String, String> remapping = new HashMap<>();
+      remapping.put(prototypeClassBytecodeName, classBytecodeName(specializedClassName));
+      for (Map.Entry<Class<?>, Class<?>> classRemappingEntry : classRemapping.entrySet()) {
+        Class<?> sourceClass = classRemappingEntry.getKey();
+        Class<?> remappingClass = classRemappingEntry.getValue();
+        remapping.put(classBytecodeName(sourceClass.getName()), classBytecodeName(remappingClass.getName()));
+      }
+      return remapping;
+    }
+
+    @SuppressWarnings("unchecked")
+    private Class<T> defineClass(String specializedClassName, byte[] specializedClassBytecode)
+    {
+      return (Class<T>) UNSAFE.defineClass(
+          specializedClassName,
+          specializedClassBytecode,
+          0,
+          specializedClassBytecode.length,
+          prototypeClass.getClassLoader(),
+          prototypeClass.getProtectionDomain()
+      );
+    }
+
+    /**
+     * No synchronization, because {@link #specialize} is called only from {@link #classSpecializationExecutor}, i. e.
+     * from a single thread.
+     */
+    byte[] getPrototypeClassBytecode() throws IOException
+    {
+      if (prototypeClassBytecode == null) {
+        ClassLoader cl = prototypeClass.getClassLoader();
+        try (InputStream prototypeClassBytecodeStream =
+                 cl.getResourceAsStream(prototypeClassBytecodeName + ".class")) {
+          prototypeClassBytecode = ByteStreams.toByteArray(prototypeClassBytecodeStream);
+        }
+      }
+      return prototypeClassBytecode;
+    }
+
+    private static String classBytecodeName(String className)
+    {
+      return className.replace('.', '/');
+    }
+  }
+
+  private static class SpecializationId
+  {
+    private final String runtimeShape;
+    private final ImmutableMap<Class<?>, Class<?>> classRemapping;
+    private final int hashCode;
+
+    private SpecializationId(String runtimeShape, ImmutableMap<Class<?>, Class<?>> classRemapping)
+    {
+      this.runtimeShape = runtimeShape;
+      this.classRemapping = classRemapping;
+      this.hashCode = runtimeShape.hashCode() * 1000003 + classRemapping.hashCode();
+    }
+
+    @Override
+    public boolean equals(Object obj)
+    {
+      if (!(obj instanceof SpecializationId)) {
+        return false;
+      }
+      SpecializationId other = (SpecializationId) obj;
+      return runtimeShape.equals(other.runtimeShape) && classRemapping.equals(other.classRemapping);
+    }
+
+    @Override
+    public int hashCode()
+    {
+      return hashCode;
+    }
+  }
+
+  /**
+   * Accumulates the number of iterations during the last hour. (Window size = 1 hour)
+   */
+  static class WindowedLoopIterationCounter<T> extends SpecializationState<T> implements Runnable
+  {
+    private final PerPrototypeClassState<T> perPrototypeClassState;
+    private final SpecializationId specializationId;
+    /** A map with the number of iterations per each minute during the last hour */
+    private final ConcurrentMap<Long, AtomicLong> perMinuteIterations = new ConcurrentHashMap<>();
+    private final AtomicBoolean specializationScheduled = new AtomicBoolean(false);
+
+    WindowedLoopIterationCounter(
+        PerPrototypeClassState<T> perPrototypeClassState,
+        SpecializationId specializationId
+    )
+    {
+      this.perPrototypeClassState = perPrototypeClassState;
+      this.specializationId = specializationId;
+    }
+
+    @Nullable
+    @Override
+    public T getSpecialized()
+    {
+      return null;
+    }
+
+    @Override
+    public void accountLoopIterations(long loopIterations)
+    {
+      if (specializationScheduled.get()) {
+        return;
+      }
+      if (loopIterations > triggerSpecializationIterationsThreshold ||
+          addAndGetTotalIterationsOverTheLastHour(loopIterations) > triggerSpecializationIterationsThreshold) {
+        if (specializationScheduled.compareAndSet(false, true)) {
+          classSpecializationExecutor.submit(this);
+        }
+      }
+    }
+
+    private long addAndGetTotalIterationsOverTheLastHour(long newIterations)
+    {
+      long currentMillis = System.currentTimeMillis();
+      long currentMinute = TimeUnit.MILLISECONDS.toMinutes(currentMillis);
+      long minuteOneHourAgo = currentMinute - TimeUnit.HOURS.toMinutes(1);
+      long totalIterations = 0;
+      boolean currentMinutePresent = false;
+      for (Iterator<Map.Entry<Long, AtomicLong>> it = perMinuteIterations.entrySet().iterator(); it.hasNext(); ) {
+        Map.Entry<Long, AtomicLong> minuteStats = it.next();
+        long minute = minuteStats.getKey();
+        if (minute < minuteOneHourAgo) {
+          it.remove();
+        } else if (minute == currentMinute) {
+          totalIterations += minuteStats.getValue().addAndGet(newIterations);
+          currentMinutePresent = true;
+        } else {
+          totalIterations += minuteStats.getValue().get();
+        }
+      }
+      if (!currentMinutePresent) {
+        perMinuteIterations.computeIfAbsent(currentMinute, AtomicLong::new).addAndGet(newIterations);
+        totalIterations += newIterations;
+      }
+      return totalIterations;
+    }
+
+    @Override
+    public void run()
+    {
+      try {
+        T specialized;
+        if (specializedClassCounter.get() > maxSpecializations) {
+          // Don't specialize, just instantiate the prototype class and emit a warning.
+          // The "better" approach is probably to implement some kind of cache eviction from
+          // PerPrototypeClassState.specializationStates. But it might be that nobody ever hits even the current
+          // maxSpecializations limit, so implementing cache eviction is an unnecessary complexity.
+          specialized = perPrototypeClassState.prototypeClass.newInstance();
+          LOG.warn(
+              "SpecializationService couldn't make more than [%d] specializations. "
+              + "Not doing specialization for runtime shape[%s] and class remapping[%s], using the prototype class[%s]",
+              maxSpecializations,
+              specializationId.runtimeShape,
+              specializationId.classRemapping,
+              perPrototypeClassState.prototypeClass
+          );
+        } else if (fakeSpecialize) {
+          specialized = perPrototypeClassState.prototypeClass.newInstance();
+        } else {
+          specialized = perPrototypeClassState.specialize(specializationId.classRemapping);
+        }
+        perPrototypeClassState.specializationStates.put(specializationId, new Specialized<>(specialized));
+      }
+      catch (Exception e) {
+        LOG.error(
+            e,
+            "Error specializing prototype class[%s] for runtime shape[%s] and class remapping[%s]",
+            perPrototypeClassState.prototypeClass,
+            specializationId.runtimeShape,
+            specializationId.classRemapping
+        );
+      }
+    }
+  }
+
+  static class Specialized<T> extends SpecializationState<T>
+  {
+    private final T specialized;
+
+    Specialized(T specialized)
+    {
+      this.specialized = specialized;
+    }
+
+    @Override
+    public T getSpecialized()
+    {
+      return specialized;
+    }
+
+    @Override
+    public void accountLoopIterations(long loopIterations)
+    {
+      // do nothing
+    }
+  }
+
+  private SpecializationService()
+  {
+  }
+}

processing/src/main/java/io/druid/query/monomorphicprocessing/SpecializationState.java

@@ -0,0 +1,52 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.monomorphicprocessing;
+
+import javax.annotation.Nullable;
+
+/**
+ * @param <T> type of query processing algorithm
+ * @see SpecializationService
+ */
+public abstract class SpecializationState<T>
+{
+  /**
+   * Returns an instance of specialized version of query processing algorithm, if available, null otherwise.
+   */
+  @Nullable
+  public abstract T getSpecialized();
+
+  /**
+   * Returns an instance of specialized version of query processing algorithm, if available, defaultInstance otherwise.
+   */
+  public final T getSpecializedOrDefault(T defaultInstance)
+  {
+    T specialized = getSpecialized();
+    return specialized != null ? specialized : defaultInstance;
+  }
+
+  /**
+   * Accounts the number of loop iterations, made when processing queries without specialized algorithm, i. e. after
+   * {@link #getSpecialized()} returned null. If sufficiently many loop iterations were made, {@link
+   * SpecializationService} decides that the algorithm is worth to be specialized, and {@link #getSpecialized()} will
+   * return non-null during later queries.
+   */
+  public abstract void accountLoopIterations(long loopIterations);
+}

processing/src/main/java/io/druid/query/monomorphicprocessing/StringRuntimeShape.java

@@ -0,0 +1,193 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.monomorphicprocessing;
+
+import javax.annotation.Nullable;
+import java.nio.ByteBuffer;
+
+/**
+ * Class to be used to obtain String representation of runtime shape of one or several {@link HotLoopCallee}s.
+ * Example:
+ *
+ * String offsetShape = StringRuntimeShape.of(offset);
+ * String dimensionSelectorShape = StringRuntimeShape.of(dimensionSelector);
+ */
+public final class StringRuntimeShape
+{
+
+  public static String of(HotLoopCallee hotLoopCallee)
+  {
+    return new Inspector().runtimeShapeOf(hotLoopCallee);
+  }
+
+  public static String of(HotLoopCallee... hotLoopCallees)
+  {
+    return new Inspector().runtimeShapeOf(hotLoopCallees);
+  }
+
+  private StringRuntimeShape()
+  {
+  }
+
+  private static class Inspector implements RuntimeShapeInspector
+  {
+    private final StringBuilder sb = new StringBuilder();
+    private int indent = 0;
+
+    String runtimeShapeOf(HotLoopCallee hotLoopCallee)
+    {
+      visit(hotLoopCallee);
+      return sb.toString();
+    }
+
+    String runtimeShapeOf(HotLoopCallee[] hotLoopCallees)
+    {
+      for (HotLoopCallee hotLoopCallee : hotLoopCallees) {
+        visit(hotLoopCallee);
+        sb.append(",\n");
+      }
+      sb.setLength(sb.length() - 2);
+      return sb.toString();
+    }
+
+    private void indent()
+    {
+      for (int i = 0; i < indent; i++) {
+        sb.append(' ');
+      }
+    }
+
+    private void incrementIndent()
+    {
+      indent += 2;
+    }
+
+    private void decrementIndent()
+    {
+      indent -= 2;
+    }
+
+    private void visit(@Nullable Object value)
+    {
+      if (value == null) {
+        sb.append("null");
+        return;
+      }
+      sb.append(value.getClass().getName());
+      if (value instanceof HotLoopCallee) {
+        appendHotLoopCalleeShape((HotLoopCallee) value);
+      } else if (value instanceof ByteBuffer) {
+        // ByteBuffers are treated specially because the byte order is an important part of the runtime shape.
+        appendByteBufferShape((ByteBuffer) value);
+      }
+    }
+
+    private void appendHotLoopCalleeShape(HotLoopCallee value)
+    {
+      sb.append(" {\n");
+      int lengthBeforeInspection = sb.length();
+      incrementIndent();
+      value.inspectRuntimeShape(this);
+      decrementIndent();
+      if (sb.length() == lengthBeforeInspection) {
+        // remove " {\n"
+        sb.setLength(lengthBeforeInspection - 3);
+      } else {
+        removeLastComma();
+        indent();
+        sb.append('}');
+      }
+    }
+
+    private void appendByteBufferShape(ByteBuffer byteBuffer)
+    {
+      sb.append(" {order: ");
+      sb.append(byteBuffer.order().toString());
+      sb.append('}');
+    }
+
+    private void removeLastComma()
+    {
+      assert sb.charAt(sb.length() - 2) == ',' && sb.charAt(sb.length() - 1) == '\n';
+      sb.setCharAt(sb.length() - 2, '\n');
+      sb.setLength(sb.length() - 1);
+    }
+
+    @Override
+    public void visit(String fieldName, @Nullable HotLoopCallee value)
+    {
+      visit(fieldName, (Object) value);
+    }
+
+    @Override
+    public void visit(String fieldName, @Nullable Object value)
+    {
+      indent();
+      sb.append(fieldName);
+      sb.append(": ");
+      visit(value);
+      sb.append(",\n");
+    }
+
+    @Override
+    public <T> void visit(String fieldName, T[] values)
+    {
+      indent();
+      sb.append(fieldName);
+      sb.append(": [\n");
+      int lengthBeforeInspection = sb.length();
+      incrementIndent();
+      for (T value : values) {
+        indent();
+        visit(value);
+        sb.append(",\n");
+      }
+      decrementIndent();
+      if (sb.length() == lengthBeforeInspection) {
+        sb.setCharAt(lengthBeforeInspection - 1, ']');
+      } else {
+        removeLastComma();
+        indent();
+        sb.append(']');
+      }
+      sb.append(",\n");
+    }
+
+    @Override
+    public void visit(String flagName, boolean flagValue)
+    {
+      indent();
+      sb.append(flagName);
+      sb.append(": ");
+      sb.append(flagValue);
+      sb.append(",\n");
+    }
+
+    @Override
+    public void visit(String key, String runtimeShape)
+    {
+      indent();
+      sb.append(key);
+      sb.append(": ");
+      sb.append(runtimeShape);
+      sb.append(",\n");
+    }
+  }
+}

processing/src/main/java/io/druid/query/topn/Generic1AggPooledTopNScanner.java

@@ -0,0 +1,43 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.topn;
+
+import io.druid.query.aggregation.BufferAggregator;
+import io.druid.segment.Cursor;
+import io.druid.segment.DimensionSelector;
+
+import java.nio.ByteBuffer;
+
+public interface Generic1AggPooledTopNScanner
+{
+  /**
+   * @param aggregatorSize number of bytes required by aggregator for a single aggregation
+   * @param positions a cache for positions in resultsBuffer, where specific (indexed) dimension values are aggregated
+   * @return number of scanned rows, i. e. number of steps made with the given cursor
+   */
+  long scanAndAggregate(
+      DimensionSelector dimensionSelector,
+      BufferAggregator aggregator,
+      int aggregatorSize,
+      Cursor cursor,
+      int[] positions,
+      ByteBuffer resultsBuffer
+  );
+}

processing/src/main/java/io/druid/query/topn/Generic1AggPooledTopNScannerPrototype.java

@@ -0,0 +1,64 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.topn;
+
+import io.druid.query.aggregation.BufferAggregator;
+import io.druid.segment.Cursor;
+import io.druid.segment.DimensionSelector;
+import io.druid.segment.data.IndexedInts;
+
+import java.nio.ByteBuffer;
+
+public final class Generic1AggPooledTopNScannerPrototype implements Generic1AggPooledTopNScanner
+{
+  @Override
+  public long scanAndAggregate(
+      DimensionSelector dimensionSelector,
+      BufferAggregator aggregator,
+      int aggregatorSize,
+      Cursor cursor,
+      int[] positions,
+      ByteBuffer resultsBuffer
+  )
+  {
+    long scannedRows = 0;
+    int positionToAllocate = 0;
+    while (!cursor.isDoneOrInterrupted()) {
+      final IndexedInts dimValues = dimensionSelector.getRow();
+      final int dimSize = dimValues.size();
+      for (int i = 0; i < dimSize; i++) {
+        int dimIndex = dimValues.get(i);
+        int position = positions[dimIndex];
+        if (position >= 0) {
+          aggregator.aggregate(resultsBuffer, position);
+        } else if (position == TopNAlgorithm.INIT_POSITION_VALUE) {
+          positions[dimIndex] = positionToAllocate;
+          position = positionToAllocate;
+          aggregator.init(resultsBuffer, position);
+          aggregator.aggregate(resultsBuffer, position);
+          positionToAllocate += aggregatorSize;
+        }
+      }
+      scannedRows++;
+      cursor.advanceUninterruptibly();
+    }
+    return scannedRows;
+  }
+}

processing/src/main/java/io/druid/query/topn/Generic2AggPooledTopNScanner.java

@@ -0,0 +1,46 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.topn;
+
+import io.druid.query.aggregation.BufferAggregator;
+import io.druid.segment.Cursor;
+import io.druid.segment.DimensionSelector;
+
+import java.nio.ByteBuffer;
+
+public interface Generic2AggPooledTopNScanner
+{
+  /**
+   * @param aggregator1Size number of bytes required by aggregator1 for a single aggregation
+   * @param aggregator2Size number of bytes required by aggregator2 for a single aggregation
+   * @param positions a cache for positions in resultsBuffer, where specific (indexed) dimension values are aggregated
+   * @return number of scanned rows, i. e. number of steps made with the given cursor
+   */
+  long scanAndAggregate(
+      DimensionSelector dimensionSelector,
+      BufferAggregator aggregator1,
+      int aggregator1Size,
+      BufferAggregator aggregator2,
+      int aggregator2Size,
+      Cursor cursor,
+      int[] positions,
+      ByteBuffer resultsBuffer
+  );
+}

processing/src/main/java/io/druid/query/topn/Generic2AggPooledTopNScannerPrototype.java

@@ -0,0 +1,71 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.topn;
+
+import io.druid.query.aggregation.BufferAggregator;
+import io.druid.segment.Cursor;
+import io.druid.segment.DimensionSelector;
+import io.druid.segment.data.IndexedInts;
+
+import java.nio.ByteBuffer;
+
+public final class Generic2AggPooledTopNScannerPrototype implements Generic2AggPooledTopNScanner
+{
+  @Override
+  public long scanAndAggregate(
+      DimensionSelector dimensionSelector,
+      BufferAggregator aggregator1,
+      int aggregator1Size,
+      BufferAggregator aggregator2,
+      int aggregator2Size,
+      Cursor cursor,
+      int[] positions,
+      ByteBuffer resultsBuffer
+  )
+  {
+    int totalAggregatorsSize = aggregator1Size + aggregator2Size;
+    long scannedRows = 0;
+    int positionToAllocate = 0;
+    while (!cursor.isDoneOrInterrupted()) {
+      final IndexedInts dimValues = dimensionSelector.getRow();
+      final int dimSize = dimValues.size();
+      for (int i = 0; i < dimSize; i++) {
+        int dimIndex = dimValues.get(i);
+        int position = positions[dimIndex];
+        if (position >= 0) {
+          aggregator1.aggregate(resultsBuffer, position);
+          aggregator2.aggregate(resultsBuffer, position + aggregator1Size);
+        } else if (position == TopNAlgorithm.INIT_POSITION_VALUE) {
+          positions[dimIndex] = positionToAllocate;
+          position = positionToAllocate;
+          aggregator1.init(resultsBuffer, position);
+          aggregator1.aggregate(resultsBuffer, position);
+          position += aggregator1Size;
+          aggregator2.init(resultsBuffer, position);
+          aggregator2.aggregate(resultsBuffer, position);
+          positionToAllocate += totalAggregatorsSize;
+        }
+      }
+      scannedRows++;
+      cursor.advanceUninterruptibly();
+    }
+    return scannedRows;
+  }
+}

processing/src/main/java/io/druid/query/topn/PooledTopNAlgorithm.java

@@ -19,13 +19,18 @@
 
 package io.druid.query.topn;
 
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Function;
 import io.druid.collections.ResourceHolder;
 import io.druid.collections.StupidPool;
 import io.druid.java.util.common.Pair;
 import io.druid.java.util.common.guava.CloseQuietly;
-import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.BaseQuery;
 import io.druid.query.ColumnSelectorPlus;
+import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.monomorphicprocessing.SpecializationService;
+import io.druid.query.monomorphicprocessing.SpecializationState;
+import io.druid.query.monomorphicprocessing.StringRuntimeShape;
 import io.druid.segment.Capabilities;
 import io.druid.segment.Cursor;
 import io.druid.segment.DimensionSelector;
@@ -40,6 +45,19 @@ import java.util.Arrays;
 public class PooledTopNAlgorithm
     extends BaseTopNAlgorithm<int[], BufferAggregator[], PooledTopNAlgorithm.PooledTopNParams>
 {
+  /** Non-final fields for testing, see TopNQueryRunnerTest */
+  @VisibleForTesting
+  static boolean specializeGeneric1AggPooledTopN =
+      !Boolean.getBoolean("dontSpecializeGeneric1AggPooledTopN");
+  @VisibleForTesting
+  static boolean specializeGeneric2AggPooledTopN =
+      !Boolean.getBoolean("dontSpecializeGeneric2AggPooledTopN");
+
+  private static final Generic1AggPooledTopNScanner defaultGeneric1AggScanner =
+      new Generic1AggPooledTopNScannerPrototype();
+  private static final Generic2AggPooledTopNScanner defaultGeneric2AggScanner =
+      new Generic2AggPooledTopNScannerPrototype();
+
   private final Capabilities capabilities;
   private final TopNQuery query;
   private final StupidPool<ByteBuffer> bufferPool;
@@ -166,6 +184,75 @@ public class PooledTopNAlgorithm
   {
     return makeBufferAggregators(params.getCursor(), query.getAggregatorSpecs());
   }
+
+  @Override
+  protected void scanAndAggregate(
+      final PooledTopNParams params,
+      final int[] positions,
+      final BufferAggregator[] theAggregators,
+      final int numProcessed
+  )
+  {
+    final Cursor cursor = params.getCursor();
+    if (specializeGeneric1AggPooledTopN && theAggregators.length == 1) {
+      scanAndAggregateGeneric1Agg(params, positions, theAggregators[0], cursor);
+    } else if (specializeGeneric2AggPooledTopN && theAggregators.length == 2) {
+      scanAndAggregateGeneric2Agg(params, positions, theAggregators, cursor);
+    } else {
+      scanAndAggregateDefault(params, positions, theAggregators);
+    }
+    BaseQuery.checkInterrupted();
+  }
+
+  private static void scanAndAggregateGeneric1Agg(
+      PooledTopNParams params,
+      int[] positions,
+      BufferAggregator aggregator,
+      Cursor cursor
+  )
+  {
+    String runtimeShape = StringRuntimeShape.of(aggregator);
+    Class<? extends Generic1AggPooledTopNScanner> prototypeClass = Generic1AggPooledTopNScannerPrototype.class;
+    SpecializationState<Generic1AggPooledTopNScanner> specializationState = SpecializationService
+        .getSpecializationState(prototypeClass, runtimeShape);
+    Generic1AggPooledTopNScanner scanner = specializationState.getSpecializedOrDefault(defaultGeneric1AggScanner);
+    long scannedRows = scanner.scanAndAggregate(
+        params.getDimSelector(),
+        aggregator,
+        params.getAggregatorSizes()[0],
+        cursor,
+        positions,
+        params.getResultsBuf()
+    );
+    specializationState.accountLoopIterations(scannedRows);
+  }
+
+  private static void scanAndAggregateGeneric2Agg(
+      PooledTopNParams params,
+      int[] positions,
+      BufferAggregator[] theAggregators,
+      Cursor cursor
+  )
+  {
+    String runtimeShape = StringRuntimeShape.of(theAggregators);
+    Class<? extends Generic2AggPooledTopNScanner> prototypeClass = Generic2AggPooledTopNScannerPrototype.class;
+    SpecializationState<Generic2AggPooledTopNScanner> specializationState = SpecializationService
+        .getSpecializationState(prototypeClass, runtimeShape);
+    Generic2AggPooledTopNScanner scanner = specializationState.getSpecializedOrDefault(defaultGeneric2AggScanner);
+    int[] aggregatorSizes = params.getAggregatorSizes();
+    long scannedRows = scanner.scanAndAggregate(
+        params.getDimSelector(),
+        theAggregators[0],
+        aggregatorSizes[0],
+        theAggregators[1],
+        aggregatorSizes[1],
+        cursor,
+        positions,
+        params.getResultsBuf()
+    );
+    specializationState.accountLoopIterations(scannedRows);
+  }
+
   /**
    * Use aggressive loop unrolling to aggregate the data
    *
@@ -184,12 +271,10 @@ public class PooledTopNAlgorithm
    * still optimizes the high quantity of aggregate queries which benefit greatly from any speed improvements
    * (they simply take longer to start with).
    */
-  @Override
-  protected void scanAndAggregate(
+  private static void scanAndAggregateDefault(
       final PooledTopNParams params,
       final int[] positions,
-      final BufferAggregator[] theAggregators,
-      final int numProcessed
+      final BufferAggregator[] theAggregators
   )
   {
     if (params.getCardinality() < 0) {
@@ -211,8 +296,7 @@ public class PooledTopNAlgorithm
     final int aggSize = theAggregators.length;
     final int aggExtra = aggSize % AGG_UNROLL_COUNT;
     int currentPosition = 0;
-
-    while (!cursor.isDone()) {
+    while (!cursor.isDoneOrInterrupted()) {
       final IndexedInts dimValues = dimSelector.getRow();
 
       final int dimSize = dimValues.size();
@@ -393,7 +477,7 @@ public class PooledTopNAlgorithm
             currentPosition
         );
       }
-      cursor.advance();
+      cursor.advanceUninterruptibly();
     }
   }
 

processing/src/main/java/io/druid/query/topn/TopNQueryBuilder.java

@@ -310,9 +310,10 @@ public class TopNQueryBuilder
     return this;
   }
 
-  public TopNQueryBuilder aggregators(List<AggregatorFactory> a)
+  @SuppressWarnings("unchecked")
+  public TopNQueryBuilder aggregators(List<? extends AggregatorFactory> a)
   {
-    aggregatorSpecs = a;
+    aggregatorSpecs = (List<AggregatorFactory>) a;
     return this;
   }
 

processing/src/main/java/io/druid/segment/BitmapOffset.java

@@ -23,10 +23,17 @@ import io.druid.collections.bitmap.BitmapFactory;
 import io.druid.collections.bitmap.ImmutableBitmap;
 import io.druid.collections.bitmap.MutableBitmap;
 import io.druid.collections.bitmap.WrappedImmutableRoaringBitmap;
+import io.druid.collections.bitmap.WrappedRoaringBitmap;
+import io.druid.extendedset.intset.EmptyIntIterator;
+import io.druid.java.util.common.RE;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.data.Offset;
 import io.druid.segment.data.RoaringBitmapSerdeFactory;
 import org.roaringbitmap.IntIterator;
 
+import java.util.Arrays;
+import java.util.HashSet;
+
 /**
  */
 public class BitmapOffset implements Offset
@@ -34,12 +41,93 @@ public class BitmapOffset implements Offset
   private static final int INVALID_VALUE = -1;
   private static final BitmapFactory ROARING_BITMAP_FACTORY = new RoaringBitmapSerdeFactory(false).getBitmapFactory();
 
-  private final IntIterator itr;
-  private final BitmapFactory bitmapFactory;
-  private final ImmutableBitmap bitmapIndex;
-  private final boolean descending;
+  /**
+   * Currently the default stops are not consciously optimized for the goals described in {@link #factorizeFullness}.
+   * They are chosen intuitively. There was no experimentation with different bitmapFullnessFactorizationStops.
+   * Experimentation and performance feedback with a different set of stops is welcome.
+   */
+  private static final String DEFAULT_FULLNESS_FACTORIZATION_STOPS = "0.01,0.1,0.3,0.5,0.7,0.9,0.99";
+  private static final double[] BITMAP_FULLNESS_FACTORIZATION_STOPS;
+  private static final String[] FACTORIZED_FULLNESS;
+  static
+  {
+    String stopString = System.getProperty("bitmapFullnessFactorizationStops", DEFAULT_FULLNESS_FACTORIZATION_STOPS);
+    String[] stopsArray = stopString.split(",");
+    if (stopsArray.length == 0) {
+      throw new RE("Empty bitmapFullnessFactorizationStops: " + stopString);
+    }
+    if (new HashSet<>(Arrays.asList(stopsArray)).size() != stopsArray.length) {
+      throw new RE("Non unique bitmapFullnessFactorizationStops: " + stopString);
+    }
 
-  private volatile int val;
+    BITMAP_FULLNESS_FACTORIZATION_STOPS = new double[stopsArray.length];
+    for (int i = 0; i < stopsArray.length; i++) {
+      String stop = stopsArray[i];
+      BITMAP_FULLNESS_FACTORIZATION_STOPS[i] = Double.parseDouble(stop);
+
+    }
+    Arrays.sort(BITMAP_FULLNESS_FACTORIZATION_STOPS);
+
+
+    double firstStop = BITMAP_FULLNESS_FACTORIZATION_STOPS[0];
+    if (Double.isNaN(firstStop) || firstStop <= 0.0) {
+      throw new RE("First bitmapFullnessFactorizationStop[%d] should be > 0", firstStop);
+    }
+    double lastStop = BITMAP_FULLNESS_FACTORIZATION_STOPS[stopsArray.length - 1];
+    if (Double.isNaN(lastStop) || lastStop >= 1) {
+      throw new RE("Last bitmapFullnessFactorizationStop[%d] should be < 1", lastStop);
+    }
+
+    String prevStop = "0";
+    FACTORIZED_FULLNESS = new String[stopsArray.length + 1];
+    for (int i = 0; i < stopsArray.length; i++) {
+      String stop = String.valueOf(BITMAP_FULLNESS_FACTORIZATION_STOPS[i]);
+      FACTORIZED_FULLNESS[i] = "(" + prevStop + ", " + stop + "]";
+      prevStop = stop;
+    }
+    FACTORIZED_FULLNESS[stopsArray.length] = "(" + prevStop + ", 1)";
+  }
+
+  /**
+   * Processing of queries with BitmapOffsets, whose Bitmaps has different factorized fullness (bucket), reported from
+   * this method, uses different copies of the same code, so JIT compiler analyzes and compiles the code for different
+   * factorized fullness separately. The goal is to capture frequency of abstraction usage in compressed bitmap
+   * algorithms, i. e.
+   *    - "Zero sequence" vs. "Literal" vs. "One sequence" in {@link io.druid.extendedset.intset.ImmutableConciseSet}
+   *    - {@link org.roaringbitmap.ArrayContainer} vs {@link org.roaringbitmap.BitmapContainer} in Roaring
+   * and then https://shipilev.net/blog/2015/black-magic-method-dispatch/ comes into play. The secondary goal is to
+   * capture HotSpot's thresholds, which it uses to compile conditional blocks differently inside bitmap impls. See
+   * https://bugs.openjdk.java.net/browse/JDK-6743900. The default BlockLayoutMinDiamondPercentage=20, i. e. if
+   * probability of taking some branch is less than 20%, it is moved out of the hot path (to save some icache?).
+   *
+   * On the other hand, we don't want to factor fullness into too small pieces, because
+   *  - too little queries may fall into those small buckets, and they are not compiled with Hotspot's C2 compiler
+   *  - if there are a lot of queries for each small factorized fullness and their copies of the code is compiled by
+   *  C2, this pollutes code cache and takes time to perform too many compilations, while some of them likely produce
+   *  identical code.
+   *
+   *  Ideally there should be as much buckets as possible as long as Hotspot's C2 output for each bucket is different.
+   */
+  private static String factorizeFullness(long bitmapCardinality, long numRows)
+  {
+    if (bitmapCardinality == 0) {
+      return "0";
+    } else if (bitmapCardinality == numRows) {
+      return "1";
+    } else {
+      double fullness = bitmapCardinality / (double) numRows;
+      int index = Arrays.binarySearch(BITMAP_FULLNESS_FACTORIZATION_STOPS, fullness);
+      if (index < 0) {
+        index = ~index;
+      }
+      return FACTORIZED_FULLNESS[index];
+    }
+  }
+
+  final IntIterator itr;
+  final String fullness;
+
+  int val;
 
   public static IntIterator getReverseBitmapOffsetIterator(ImmutableBitmap bitmapIndex)
   {
@@ -55,16 +143,25 @@ public class BitmapOffset implements Offset
     return ((WrappedImmutableRoaringBitmap) roaringBitmap).getBitmap().getReverseIntIterator();
   }
 
-  public BitmapOffset(BitmapFactory bitmapFactory, ImmutableBitmap bitmapIndex, boolean descending)
+  public static BitmapOffset of(ImmutableBitmap bitmapIndex, boolean descending, long numRows)
   {
-    this.bitmapFactory = bitmapFactory;
-    this.bitmapIndex = bitmapIndex;
-    this.descending = descending;
-    this.itr = newIterator();
+    if (bitmapIndex instanceof WrappedImmutableRoaringBitmap ||
+        bitmapIndex instanceof WrappedRoaringBitmap ||
+        descending) {
+      return new RoaringBitmapOffset(bitmapIndex, descending, numRows);
+    } else {
+      return new BitmapOffset(bitmapIndex, descending, numRows);
+    }
+  }
+
+  private BitmapOffset(ImmutableBitmap bitmapIndex, boolean descending, long numRows)
+  {
+    this.itr = newIterator(bitmapIndex, descending);
+    this.fullness = factorizeFullness(bitmapIndex.size(), numRows);
     increment();
   }
 
-  private IntIterator newIterator()
+  private IntIterator newIterator(ImmutableBitmap bitmapIndex, boolean descending)
   {
     if (!descending) {
       return bitmapIndex.iterator();
@@ -73,13 +170,11 @@ public class BitmapOffset implements Offset
     }
   }
 
-  private BitmapOffset(BitmapOffset otherOffset)
+  private BitmapOffset(String fullness, IntIterator itr, int val)
   {
-    this.bitmapFactory = otherOffset.bitmapFactory;
-    this.bitmapIndex = otherOffset.bitmapIndex;
-    this.descending = otherOffset.descending;
-    this.itr = otherOffset.itr.clone();
-    this.val = otherOffset.val;
+    this.fullness = fullness;
+    this.itr = itr;
+    this.val = val;
   }
 
   @Override
@@ -101,11 +196,7 @@ public class BitmapOffset implements Offset
   @Override
   public Offset clone()
   {
-    if (bitmapIndex == null || bitmapIndex.size() == 0) {
-      return new BitmapOffset(bitmapFactory, bitmapFactory.makeEmptyImmutableBitmap(), descending);
-    }
-
-    return new BitmapOffset(this);
+    return new BitmapOffset(fullness, itr.clone(), val);
   }
 
   @Override
@@ -113,4 +204,31 @@ public class BitmapOffset implements Offset
   {
     return val;
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("itr", itr);
+    inspector.visit("fullness", fullness);
+  }
+
+  public static class RoaringBitmapOffset extends BitmapOffset
+  {
+
+    public RoaringBitmapOffset(ImmutableBitmap bitmapIndex, boolean descending, long numRows)
+    {
+      super(bitmapIndex, descending, numRows);
+    }
+
+    RoaringBitmapOffset(String fullness, IntIterator itr, int val)
+    {
+      super(fullness, itr, val);
+    }
+
+    @Override
+    public Offset clone()
+    {
+      return new RoaringBitmapOffset(fullness, itr.hasNext() ? itr.clone() : EmptyIntIterator.instance(), val);
+    }
+  }
 }

processing/src/main/java/io/druid/segment/Cursor.java

@@ -24,9 +24,11 @@ package io.druid.segment;import org.joda.time.DateTime;
 
 public interface Cursor extends ColumnSelectorFactory
 {
-  public DateTime getTime();
-  public void advance();
-  public void advanceTo(int offset);
-  public boolean isDone();
-  public void reset();
+  DateTime getTime();
+  void advance();
+  void advanceUninterruptibly();
+  void advanceTo(int offset);
+  boolean isDone();
+  boolean isDoneOrInterrupted();
+  void reset();
 }

processing/src/main/java/io/druid/segment/DimensionSelector.java

@@ -21,13 +21,15 @@ package io.druid.segment;
 
 import com.google.common.base.Predicate;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.CalledFromHotLoop;
+import io.druid.query.monomorphicprocessing.HotLoopCallee;
 import io.druid.segment.data.IndexedInts;
 
 import javax.annotation.Nullable;
 
 /**
  */
-public interface DimensionSelector extends ColumnValueSelector
+public interface DimensionSelector extends ColumnValueSelector, HotLoopCallee
 {
   public static int CARDINALITY_UNKNOWN = -1;
 
@@ -38,6 +40,7 @@ public interface DimensionSelector extends ColumnValueSelector
    *
    * @return all values for the row as an IntBuffer
    */
+  @CalledFromHotLoop
   public IndexedInts getRow();
 
   /**
@@ -90,6 +93,7 @@ public interface DimensionSelector extends ColumnValueSelector
    * @param id id to lookup the field name for
    * @return the field name for the given id
    */
+  @CalledFromHotLoop
   public String lookupName(int id);
 
   /**

processing/src/main/java/io/druid/segment/FloatColumnSelector.java

@@ -19,12 +19,16 @@
 
 package io.druid.segment;
 
+import io.druid.query.monomorphicprocessing.CalledFromHotLoop;
+import io.druid.query.monomorphicprocessing.HotLoopCallee;
+
 /**
  * An object that gets a metric value.  Metric values are always floats and there is an assumption that the
  * FloatColumnSelector has a handle onto some other stateful object (e.g. an Offset) which is changing between calls
  * to get() (though, that doesn't have to be the case if you always want the same value...).
  */
-public interface FloatColumnSelector extends ColumnValueSelector
+public interface FloatColumnSelector extends ColumnValueSelector, HotLoopCallee
 {
+  @CalledFromHotLoop
   public float get();
 }

processing/src/main/java/io/druid/segment/FloatDimensionIndexer.java

@@ -22,6 +22,7 @@ package io.druid.segment;
 import io.druid.collections.bitmap.BitmapFactory;
 import io.druid.collections.bitmap.MutableBitmap;
 import io.druid.query.dimension.DimensionSpec;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.column.ValueType;
 import io.druid.segment.data.Indexed;
 import io.druid.segment.incremental.IncrementalIndex;
@@ -115,6 +116,11 @@ public class FloatDimensionIndexer implements DimensionIndexer<Float, Float, Flo
         float floatVal = (Float) dims[dimIndex];
         return (long) floatVal;
       }
+
+      @Override
+      public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+      {
+      }
     }
 
     return new IndexerLongColumnSelector();
@@ -140,6 +146,11 @@ public class FloatDimensionIndexer implements DimensionIndexer<Float, Float, Flo
 
         return (Float) dims[dimIndex];
       }
+
+      @Override
+      public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+      {
+      }
     }
 
     return new IndexerFloatColumnSelector();

processing/src/main/java/io/druid/segment/FloatWrappingDimensionSelector.java

@@ -20,6 +20,7 @@
 package io.druid.segment;
 
 import io.druid.query.extraction.ExtractionFn;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.virtual.BaseSingleValueDimensionSelector;
 
 public class FloatWrappingDimensionSelector extends BaseSingleValueDimensionSelector
@@ -42,4 +43,11 @@ public class FloatWrappingDimensionSelector extends BaseSingleValueDimensionSele
       return extractionFn.apply(selector.get());
     }
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+    inspector.visit("extractionFn", extractionFn);
+  }
 }

processing/src/main/java/io/druid/segment/LongColumnSelector.java

@@ -19,9 +19,13 @@
 
 package io.druid.segment;
 
+import io.druid.query.monomorphicprocessing.CalledFromHotLoop;
+import io.druid.query.monomorphicprocessing.HotLoopCallee;
+
 /**
  */
-public interface LongColumnSelector extends ColumnValueSelector
+public interface LongColumnSelector extends ColumnValueSelector, HotLoopCallee
 {
+  @CalledFromHotLoop
   public long get();
 }

processing/src/main/java/io/druid/segment/LongDimensionIndexer.java

@@ -22,6 +22,7 @@ package io.druid.segment;
 import io.druid.collections.bitmap.BitmapFactory;
 import io.druid.collections.bitmap.MutableBitmap;
 import io.druid.query.dimension.DimensionSpec;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.column.ValueType;
 import io.druid.segment.data.Indexed;
 import io.druid.segment.incremental.IncrementalIndex;
@@ -114,6 +115,11 @@ public class LongDimensionIndexer implements DimensionIndexer<Long, Long, Long>
 
         return (Long) dims[dimIndex];
       }
+
+      @Override
+      public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+      {
+      }
     }
 
     return new IndexerLongColumnSelector();
@@ -140,6 +146,11 @@ public class LongDimensionIndexer implements DimensionIndexer<Long, Long, Long>
         long longVal = (Long) dims[dimIndex];
         return (float) longVal;
       }
+
+      @Override
+      public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+      {
+      }
     }
 
     return new IndexerFloatColumnSelector();

processing/src/main/java/io/druid/segment/LongWrappingDimensionSelector.java

@@ -20,6 +20,7 @@
 package io.druid.segment;
 
 import io.druid.query.extraction.ExtractionFn;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.virtual.BaseSingleValueDimensionSelector;
 
 public class LongWrappingDimensionSelector extends BaseSingleValueDimensionSelector
@@ -42,4 +43,11 @@ public class LongWrappingDimensionSelector extends BaseSingleValueDimensionSelec
       return extractionFn.apply(selector.get());
     }
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+    inspector.visit("extractionFn", extractionFn);
+  }
 }

processing/src/main/java/io/druid/segment/NullDimensionSelector.java

@@ -22,6 +22,7 @@ package io.druid.segment;
 import com.google.common.base.Predicate;
 import com.google.common.base.Strings;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.data.IndexedInts;
 import io.druid.segment.data.ZeroIndexedInts;
 import io.druid.segment.filter.BooleanValueMatcher;
@@ -91,4 +92,9 @@ public class NullDimensionSelector implements DimensionSelector, IdLookup
   {
     return Strings.isNullOrEmpty(name) ? 0 : -1;
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+  }
 }

processing/src/main/java/io/druid/segment/ObjectColumnSelector.java

@@ -19,8 +19,12 @@
 
 package io.druid.segment;
 
+import io.druid.query.monomorphicprocessing.CalledFromHotLoop;
+
 public interface ObjectColumnSelector<T> extends ColumnValueSelector
 {
   public Class<T> classOfObject();
+
+  @CalledFromHotLoop
   public T get();
 }

processing/src/main/java/io/druid/segment/QueryableIndexStorageAdapter.java

@@ -31,13 +31,14 @@ import io.druid.collections.bitmap.ImmutableBitmap;
 import io.druid.java.util.common.granularity.Granularity;
 import io.druid.java.util.common.guava.Sequence;
 import io.druid.java.util.common.guava.Sequences;
-import io.druid.query.QueryInterruptedException;
+import io.druid.query.BaseQuery;
 import io.druid.query.dimension.DimensionSpec;
 import io.druid.query.extraction.ExtractionFn;
 import io.druid.query.filter.BooleanFilter;
 import io.druid.query.filter.Filter;
 import io.druid.query.filter.RowOffsetMatcherFactory;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.column.BitmapIndex;
 import io.druid.segment.column.Column;
 import io.druid.segment.column.ColumnCapabilities;
@@ -274,10 +275,10 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
         offset = new NoFilterOffset(0, index.getNumRows(), descending);
       } else {
         // Use AndFilter.getBitmapIndex to intersect the preFilters to get its short-circuiting behavior.
-        offset = new BitmapOffset(
-            selector.getBitmapFactory(),
+        offset = BitmapOffset.of(
             AndFilter.getBitmapIndex(selector, preFilters),
-            descending
+            descending,
+            (long) getNumRows()
         );
       }
     }
@@ -472,10 +473,20 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
 
                       final DictionaryEncodedColumn<String> column = cachedColumn;
 
+                      abstract class QueryableDimensionSelector implements DimensionSelector, IdLookup
+                      {
+                        @Override
+                        public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+                        {
+                          inspector.visit("column", column);
+                          inspector.visit("cursorOffset", cursorOffset);
+                          inspector.visit("extractionFn", extractionFn);
+                        }
+                      }
                       if (column == null) {
                         return NullDimensionSelector.instance();
                       } else if (columnDesc.getCapabilities().hasMultipleValues()) {
-                        class MultiValueDimensionSelector implements DimensionSelector, IdLookup
+                        class MultiValueDimensionSelector extends QueryableDimensionSelector
                         {
                           @Override
                           public IndexedInts getRow()
@@ -536,7 +547,7 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
                         }
                         return new MultiValueDimensionSelector();
                       } else {
-                        class SingleValueDimensionSelector implements DimensionSelector, IdLookup
+                        class SingleValueDimensionSelector extends QueryableDimensionSelector
                         {
                           @Override
                           public IndexedInts getRow()
@@ -690,6 +701,13 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
                         {
                           return metricVals.getFloatSingleValueRow(cursorOffset.getOffset());
                         }
+
+                        @Override
+                        public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+                        {
+                          inspector.visit("metricVals", metricVals);
+                          inspector.visit("cursorOffset", cursorOffset);
+                        }
                       };
                     }
 
@@ -724,6 +742,13 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
                         {
                           return metricVals.getLongSingleValueRow(cursorOffset.getOffset());
                         }
+
+                        @Override
+                        public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+                        {
+                          inspector.visit("metricVals", metricVals);
+                          inspector.visit("cursorOffset", cursorOffset);
+                        }
                       };
                     }
 
@@ -912,9 +937,13 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
                       @Override
                       public void advance()
                       {
-                        if (Thread.interrupted()) {
-                          throw new QueryInterruptedException(new InterruptedException());
+                        BaseQuery.checkInterrupted();
+                        cursorOffset.increment();
                       }
+
+                      @Override
+                      public void advanceUninterruptibly()
+                      {
                         cursorOffset.increment();
                       }
 
@@ -934,6 +963,12 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
                         return !cursorOffset.withinBounds();
                       }
 
+                      @Override
+                      public boolean isDoneOrInterrupted()
+                      {
+                        return isDone() || Thread.currentThread().isInterrupted();
+                      }
+
                       @Override
                       public void reset()
                       {
@@ -981,15 +1016,28 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
                       @Override
                       public void advance()
                       {
-                        if (Thread.interrupted()) {
-                          throw new QueryInterruptedException(new InterruptedException());
-                        }
+                        BaseQuery.checkInterrupted();
                         cursorOffset.increment();
 
                         while (!isDone()) {
-                          if (Thread.interrupted()) {
-                            throw new QueryInterruptedException(new InterruptedException());
+                          BaseQuery.checkInterrupted();
+                          if (filterMatcher.matches()) {
+                            return;
+                          } else {
+                            cursorOffset.increment();
                           }
+                        }
+                      }
+
+                      @Override
+                      public void advanceUninterruptibly()
+                      {
+                        if (Thread.currentThread().isInterrupted()) {
+                          return;
+                        }
+                        cursorOffset.increment();
+
+                        while (!isDoneOrInterrupted()) {
                           if (filterMatcher.matches()) {
                             return;
                           } else {
@@ -1014,6 +1062,12 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
                         return !cursorOffset.withinBounds();
                       }
 
+                      @Override
+                      public boolean isDoneOrInterrupted()
+                      {
+                        return isDone() || Thread.currentThread().isInterrupted();
+                      }
+
                       @Override
                       public void reset()
                       {
@@ -1166,6 +1220,14 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
     {
       throw new IllegalStateException("clone");
     }
+
+    @Override
+    public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+    {
+      inspector.visit("baseOffset", baseOffset);
+      inspector.visit("timestamps", timestamps);
+      inspector.visit("allWithinThreshold", allWithinThreshold);
+    }
   }
 
   private static class AscendingTimestampCheckingOffset extends TimestampCheckingOffset
@@ -1275,6 +1337,12 @@ public class QueryableIndexStorageAdapter implements StorageAdapter
     {
       return currentOffset + "/" + rowCount + (descending ? "(DSC)" : "");
     }
+
+    @Override
+    public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+    {
+      inspector.visit("descending", descending);
+    }
   }
 
   @Override

processing/src/main/java/io/druid/segment/SingleScanTimeDimSelector.java

@@ -22,6 +22,7 @@ package io.druid.segment;
 import com.google.common.base.Predicate;
 import io.druid.query.extraction.ExtractionFn;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.data.IndexedInts;
 import io.druid.segment.data.SingleIndexedInt;
 
@@ -156,4 +157,12 @@ public class SingleScanTimeDimSelector implements DimensionSelector
   {
     return null;
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("selector", selector);
+    inspector.visit("extractionFn", extractionFn);
+    inspector.visit("descending", descending);
+  }
 }

processing/src/main/java/io/druid/segment/StringDimensionIndexer.java

@@ -32,6 +32,7 @@ import io.druid.data.input.impl.DimensionSchema.MultiValueHandling;
 import io.druid.query.dimension.DimensionSpec;
 import io.druid.query.extraction.ExtractionFn;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.column.ValueType;
 import io.druid.segment.data.ArrayBasedIndexedInts;
 import io.druid.segment.data.Indexed;
@@ -541,6 +542,12 @@ public class StringDimensionIndexer implements DimensionIndexer<Integer, int[],
         }
         return getEncodedValue(name, false);
       }
+
+      @Override
+      public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+      {
+        inspector.visit("currEntry", currEntry);
+      }
     }
     return new IndexerDimensionSelector();
   }

processing/src/main/java/io/druid/segment/ZeroFloatColumnSelector.java

@@ -19,6 +19,8 @@
 
 package io.druid.segment;
 
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+
 public final class ZeroFloatColumnSelector implements FloatColumnSelector
 {
   private static final ZeroFloatColumnSelector INSTANCE = new ZeroFloatColumnSelector();
@@ -38,4 +40,9 @@ public final class ZeroFloatColumnSelector implements FloatColumnSelector
   {
     return 0.0f;
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+  }
 }

processing/src/main/java/io/druid/segment/ZeroLongColumnSelector.java

@@ -19,6 +19,8 @@
 
 package io.druid.segment;
 
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+
 public final class ZeroLongColumnSelector implements LongColumnSelector
 {
   private static final ZeroLongColumnSelector INSTANCE = new ZeroLongColumnSelector();
@@ -38,4 +40,9 @@ public final class ZeroLongColumnSelector implements LongColumnSelector
   {
     return 0;
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+  }
 }

processing/src/main/java/io/druid/segment/column/GenericColumn.java

@@ -19,6 +19,8 @@
 
 package io.druid.segment.column;
 
+import io.druid.query.monomorphicprocessing.CalledFromHotLoop;
+import io.druid.query.monomorphicprocessing.HotLoopCallee;
 import io.druid.segment.data.Indexed;
 import io.druid.segment.data.IndexedFloats;
 import io.druid.segment.data.IndexedLongs;
@@ -27,17 +29,23 @@ import java.io.Closeable;
 
 /**
  */
-public interface GenericColumn extends Closeable
+public interface GenericColumn extends HotLoopCallee, Closeable
 {
   public int length();
   public ValueType getType();
   public boolean hasMultipleValues();
 
+  @CalledFromHotLoop
   public String getStringSingleValueRow(int rowNum);
+  @CalledFromHotLoop
   public Indexed<String> getStringMultiValueRow(int rowNum);
+  @CalledFromHotLoop
   public float getFloatSingleValueRow(int rowNum);
+  @CalledFromHotLoop
   public IndexedFloats getFloatMultiValueRow(int rowNum);
+  @CalledFromHotLoop
   public long getLongSingleValueRow(int rowNum);
+  @CalledFromHotLoop
   public IndexedLongs getLongMultiValueRow(int rowNum);
 
   @Override

processing/src/main/java/io/druid/segment/column/IndexedFloatsGenericColumn.java

@@ -19,6 +19,7 @@
 
 package io.druid.segment.column;
 
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.data.Indexed;
 import io.druid.segment.data.IndexedFloats;
 import io.druid.segment.data.IndexedLongs;
@@ -94,4 +95,10 @@ public class IndexedFloatsGenericColumn implements GenericColumn
   {
     column.close();
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("column", column);
+  }
 }

processing/src/main/java/io/druid/segment/column/IndexedLongsGenericColumn.java

@@ -19,6 +19,7 @@
 
 package io.druid.segment.column;
 
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.data.Indexed;
 import io.druid.segment.data.IndexedFloats;
 import io.druid.segment.data.IndexedLongs;
@@ -94,4 +95,10 @@ public class IndexedLongsGenericColumn implements GenericColumn
   {
     column.close();
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("column", column);
+  }
 }

processing/src/main/java/io/druid/segment/data/ArrayBasedOffset.java

@@ -19,6 +19,8 @@
 
 package io.druid.segment.data;
 
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+
 /**
  */
 public class ArrayBasedOffset implements Offset
@@ -67,4 +69,9 @@ public class ArrayBasedOffset implements Offset
     retVal.currIndex = currIndex;
     return retVal;
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+  }
 }

processing/src/main/java/io/druid/segment/data/IntersectingOffset.java

@@ -19,6 +19,8 @@
 
 package io.druid.segment.data;
 
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+
 /**
  */
 public class IntersectingOffset implements Offset {
@@ -91,4 +93,11 @@ public class IntersectingOffset implements Offset {
     final Offset rhsClone = rhs.clone();
     return new IntersectingOffset(lhsClone, rhsClone);
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("lhs", lhs);
+    inspector.visit("rhs", rhs);
+  }
 }

processing/src/main/java/io/druid/segment/data/Offset.java

@@ -19,14 +19,18 @@
 
 package io.druid.segment.data;
 
+import io.druid.query.monomorphicprocessing.CalledFromHotLoop;
+
 /**
  * The "mutable" version of a ReadableOffset.  Introduces "increment()" and "withinBounds()" methods, which are
  * very similar to "next()" and "hasNext()" on the Iterator interface except increment() does not return a value.
  */
 public interface Offset extends ReadableOffset
 {
+  @CalledFromHotLoop
   void increment();
 
+  @CalledFromHotLoop
   boolean withinBounds();
 
   Offset clone();

processing/src/main/java/io/druid/segment/data/ReadableOffset.java

@@ -19,6 +19,9 @@
 
 package io.druid.segment.data;
 
+import io.druid.query.monomorphicprocessing.CalledFromHotLoop;
+import io.druid.query.monomorphicprocessing.HotLoopCallee;
+
 /**
  * A ReadableOffset is an object that provides an integer offset, ostensibly as an index into an array.
  *
@@ -26,8 +29,9 @@ package io.druid.segment.data;
  * given to classes (e.g. FloatColumnSelector objects) by something which keeps a reference to the base Offset object
  * and increments it.
  */
-public interface ReadableOffset
+public interface ReadableOffset extends HotLoopCallee
 {
+    @CalledFromHotLoop
     int getOffset();
 }
 

processing/src/main/java/io/druid/segment/data/UnioningOffset.java

@@ -19,6 +19,8 @@
 
 package io.druid.segment.data;
 
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+
 /**
  */
 public class UnioningOffset implements Offset
@@ -135,4 +137,11 @@ public class UnioningOffset implements Offset
 
     return new UnioningOffset(newOffsets, newOffsetValues, nextOffsetIndex);
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("lhs", offsets[0]);
+    inspector.visit("rhs", offsets[1]);
+  }
 }

processing/src/main/java/io/druid/segment/incremental/IncrementalIndexStorageAdapter.java

@@ -26,11 +26,12 @@ import com.google.common.collect.Lists;
 import io.druid.java.util.common.granularity.Granularity;
 import io.druid.java.util.common.guava.Sequence;
 import io.druid.java.util.common.guava.Sequences;
-import io.druid.query.QueryInterruptedException;
+import io.druid.query.BaseQuery;
 import io.druid.query.dimension.DimensionSpec;
 import io.druid.query.extraction.ExtractionFn;
 import io.druid.query.filter.Filter;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.Capabilities;
 import io.druid.segment.Cursor;
 import io.druid.segment.DimensionHandler;
@@ -273,8 +274,31 @@ public class IncrementalIndexStorageAdapter implements StorageAdapter
                 }
 
                 while (baseIter.hasNext()) {
-                  if (Thread.interrupted()) {
-                    throw new QueryInterruptedException(new InterruptedException());
+                  BaseQuery.checkInterrupted();
+
+                  currEntry.set(baseIter.next());
+
+                  if (filterMatcher.matches()) {
+                    return;
+                  }
+                }
+
+                if (!filterMatcher.matches()) {
+                  done = true;
+                }
+              }
+
+              @Override
+              public void advanceUninterruptibly()
+              {
+                if (!baseIter.hasNext()) {
+                  done = true;
+                  return;
+                }
+
+                while (baseIter.hasNext()) {
+                  if (Thread.currentThread().isInterrupted()) {
+                    return;
                   }
 
                   currEntry.set(baseIter.next());
@@ -305,6 +329,12 @@ public class IncrementalIndexStorageAdapter implements StorageAdapter
                 return done;
               }
 
+              @Override
+              public boolean isDoneOrInterrupted()
+              {
+                return isDone() || Thread.currentThread().isInterrupted();
+              }
+
               @Override
               public void reset()
               {
@@ -316,9 +346,7 @@ public class IncrementalIndexStorageAdapter implements StorageAdapter
                   Iterators.advance(baseIter, numAdvanced);
                 }
 
-                if (Thread.interrupted()) {
-                  throw new QueryInterruptedException(new InterruptedException());
-                }
+                BaseQuery.checkInterrupted();
 
                 boolean foundMatched = false;
                 while (baseIter.hasNext()) {
@@ -414,6 +442,12 @@ public class IncrementalIndexStorageAdapter implements StorageAdapter
                   {
                     return index.getMetricFloatValue(currEntry.getValue(), metricIndex);
                   }
+
+                  @Override
+                  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+                  {
+                    inspector.visit("index", index);
+                  }
                 };
               }
 
@@ -425,14 +459,20 @@ public class IncrementalIndexStorageAdapter implements StorageAdapter
                 }
 
                 if (columnName.equals(Column.TIME_COLUMN_NAME)) {
-                  return new LongColumnSelector()
+                  class TimeLongColumnSelector implements LongColumnSelector
                   {
                     @Override
                     public long get()
                     {
                       return currEntry.getKey().getTimestamp();
                     }
-                  };
+
+                    @Override
+                    public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+                    {
+                    }
+                  }
+                  return new TimeLongColumnSelector();
                 }
 
                 final Integer dimIndex = index.getDimensionIndex(columnName);
@@ -462,6 +502,12 @@ public class IncrementalIndexStorageAdapter implements StorageAdapter
                         metricIndex
                     );
                   }
+
+                  @Override
+                  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+                  {
+                    inspector.visit("index", index);
+                  }
                 };
               }
 

processing/src/main/java/io/druid/segment/virtual/BaseSingleValueDimensionSelector.java

@@ -21,6 +21,7 @@ package io.druid.segment.virtual;
 
 import com.google.common.base.Predicate;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.CalledFromHotLoop;
 import io.druid.segment.DimensionSelector;
 import io.druid.segment.IdLookup;
 import io.druid.segment.data.IndexedInts;
@@ -31,6 +32,7 @@ import java.util.Objects;
 
 public abstract class BaseSingleValueDimensionSelector implements DimensionSelector
 {
+  @CalledFromHotLoop
   protected abstract String getValue();
 
   @Override

processing/src/main/java/io/druid/segment/virtual/ExpressionSelectors.java

@@ -21,6 +21,7 @@ package io.druid.segment.virtual;
 
 import io.druid.math.expr.Expr;
 import io.druid.query.extraction.ExtractionFn;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.ColumnSelectorFactory;
 import io.druid.segment.DimensionSelector;
 import io.druid.segment.FloatColumnSelector;
@@ -56,6 +57,12 @@ public class ExpressionSelectors
         final Number number = baseSelector.get();
         return number != null ? number.longValue() : nullValue;
       }
+
+      @Override
+      public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+      {
+        inspector.visit("baseSelector", baseSelector);
+      }
     }
     return new ExpressionLongColumnSelector();
   }
@@ -75,6 +82,12 @@ public class ExpressionSelectors
         final Number number = baseSelector.get();
         return number != null ? number.floatValue() : nullValue;
       }
+
+      @Override
+      public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+      {
+        inspector.visit("baseSelector", baseSelector);
+      }
     }
     return new ExpressionFloatColumnSelector();
   }
@@ -96,6 +109,12 @@ public class ExpressionSelectors
           final Number number = baseSelector.get();
           return number == null ? null : String.valueOf(number);
         }
+
+        @Override
+        public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+        {
+          inspector.visit("baseSelector", baseSelector);
+        }
       }
       return new DefaultExpressionDimensionSelector();
     } else {
@@ -106,6 +125,12 @@ public class ExpressionSelectors
         {
           return extractionFn.apply(baseSelector.get());
         }
+
+        @Override
+        public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+        {
+          inspector.visit("baseSelector", baseSelector);
+        }
       }
       return new ExtractionExpressionDimensionSelector();
     }

processing/src/test/java/io/druid/query/aggregation/FilteredAggregatorTest.java

@@ -36,6 +36,7 @@ import io.druid.query.filter.RegexDimFilter;
 import io.druid.query.filter.SearchQueryDimFilter;
 import io.druid.query.filter.SelectorDimFilter;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.query.ordering.StringComparators;
 import io.druid.query.search.search.ContainsSearchQuerySpec;
 import io.druid.segment.ColumnSelectorFactory;
@@ -167,6 +168,11 @@ public class FilteredAggregatorTest
                     }
                   };
                 }
+
+                @Override
+                public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+                {
+                }
               }
           );
         } else {

processing/src/test/java/io/druid/query/aggregation/MetricManipulatorFnsTest.java

@@ -21,7 +21,7 @@ package io.druid.query.aggregation;
 
 import io.druid.hll.HyperLogLogCollector;
 import io.druid.query.aggregation.hyperloglog.HyperUniquesAggregatorFactory;
-import io.druid.segment.LongColumnSelector;
+import io.druid.segment.TestLongColumnSelector;
 import org.junit.Assert;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -42,7 +42,7 @@ public class MetricManipulatorFnsTest
     final ArrayList<Object[]> constructorArrays = new ArrayList<>();
     final long longVal = 13789;
     LongMinAggregator longMinAggregator = new LongMinAggregator(
-        new LongColumnSelector()
+        new TestLongColumnSelector()
         {
           @Override
           public long get()
@@ -81,7 +81,7 @@ public class MetricManipulatorFnsTest
 
     LongSumAggregatorFactory longSumAggregatorFactory = new LongSumAggregatorFactory(NAME, FIELD);
     LongSumAggregator longSumAggregator = new LongSumAggregator(
-        new LongColumnSelector()
+        new TestLongColumnSelector()
         {
           @Override
           public long get()

processing/src/test/java/io/druid/query/aggregation/TestFloatColumnSelector.java

@@ -19,11 +19,9 @@
 
 package io.druid.query.aggregation;
 
-import io.druid.segment.FloatColumnSelector;
-
 /**
  */
-public class TestFloatColumnSelector implements FloatColumnSelector
+public class TestFloatColumnSelector extends io.druid.segment.TestFloatColumnSelector
 {
   private final float[] floats;
 

processing/src/test/java/io/druid/query/aggregation/TestLongColumnSelector.java

@@ -19,11 +19,9 @@
 
 package io.druid.query.aggregation;
 
-import io.druid.segment.LongColumnSelector;
-
 /**
  */
-public class TestLongColumnSelector implements LongColumnSelector
+public class TestLongColumnSelector extends io.druid.segment.TestLongColumnSelector
 {
   private final long[] longs;
 

processing/src/test/java/io/druid/query/aggregation/cardinality/CardinalityAggregatorBenchmark.java

@@ -44,7 +44,7 @@ public class CardinalityAggregatorBenchmark extends SimpleBenchmark
 
   CardinalityBufferAggregator agg;
   List<DimensionSelector> selectorList;
-  List<ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>> dimInfoList;
+  ColumnSelectorPlus<CardinalityAggregatorColumnSelectorStrategy>[] dimInfos;
   ByteBuffer buf;
   int pos;
 
@@ -93,12 +93,9 @@ public class CardinalityAggregatorBenchmark extends SimpleBenchmark
         (DimensionSelector) dim1
     );
 
-    dimInfoList = Lists.newArrayList(dimInfo1);
+    dimInfos = new ColumnSelectorPlus[] {dimInfo1};
 
-    agg = new CardinalityBufferAggregator(
-        dimInfoList,
-        byRow
-    );
+    agg = new CardinalityBufferAggregator(dimInfos, byRow);
 
     CardinalityAggregatorFactory factory = new CardinalityAggregatorFactory(
         "billy",

processing/src/test/java/io/druid/query/aggregation/cardinality/CardinalityAggregatorTest.java

@@ -43,6 +43,7 @@ import io.druid.query.extraction.ExtractionFn;
 import io.druid.query.extraction.JavaScriptExtractionFn;
 import io.druid.query.extraction.RegexDimExtractionFn;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.DimensionSelector;
 import io.druid.segment.DimensionSelectorUtils;
 import io.druid.segment.IdLookup;
@@ -205,6 +206,11 @@ public class CardinalityAggregatorTest
         }
       };
     }
+
+    @Override
+    public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+    {
+    }
   }
 
   /*
@@ -418,7 +424,7 @@ public class CardinalityAggregatorTest
   public void testBufferAggregateRows() throws Exception
   {
     CardinalityBufferAggregator agg = new CardinalityBufferAggregator(
-        dimInfoList,
+        dimInfoList.toArray(new ColumnSelectorPlus[] {}),
         true
     );
 
@@ -439,7 +445,7 @@ public class CardinalityAggregatorTest
   public void testBufferAggregateValues() throws Exception
   {
     CardinalityBufferAggregator agg = new CardinalityBufferAggregator(
-        dimInfoList,
+        dimInfoList.toArray(new ColumnSelectorPlus[] {}),
         false
     );
 

processing/src/test/java/io/druid/query/dimension/TestDimensionSelector.java

@@ -21,6 +21,7 @@ package io.druid.query.dimension;
 
 import com.google.common.base.Predicate;
 import io.druid.query.filter.ValueMatcher;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
 import io.druid.segment.DimensionSelector;
 import io.druid.segment.DimensionSelectorUtils;
 import io.druid.segment.IdLookup;
@@ -92,4 +93,9 @@ class TestDimensionSelector implements DimensionSelector
       }
     };
   }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+  }
 }

processing/src/test/java/io/druid/query/groupby/epinephelinae/TestColumnSelectorFactory.java

@@ -26,6 +26,8 @@ import io.druid.segment.DimensionSelector;
 import io.druid.segment.FloatColumnSelector;
 import io.druid.segment.LongColumnSelector;
 import io.druid.segment.ObjectColumnSelector;
+import io.druid.segment.TestFloatColumnSelector;
+import io.druid.segment.TestLongColumnSelector;
 import io.druid.segment.column.ColumnCapabilities;
 
 public class TestColumnSelectorFactory implements ColumnSelectorFactory
@@ -46,7 +48,7 @@ public class TestColumnSelectorFactory implements ColumnSelectorFactory
   @Override
   public FloatColumnSelector makeFloatColumnSelector(final String columnName)
   {
-    return new FloatColumnSelector()
+    return new TestFloatColumnSelector()
     {
       @Override
       public float get()
@@ -59,7 +61,7 @@ public class TestColumnSelectorFactory implements ColumnSelectorFactory
   @Override
   public LongColumnSelector makeLongColumnSelector(final String columnName)
   {
-    return new LongColumnSelector()
+    return new TestLongColumnSelector()
     {
       @Override
       public long get()

processing/src/test/java/io/druid/query/monomorphicprocessing/StringRuntimeShapeTest.java

@@ -0,0 +1,113 @@
+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.monomorphicprocessing;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.nio.ByteBuffer;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.TreeSet;
+
+public class StringRuntimeShapeTest
+{
+  static class Empty implements HotLoopCallee
+  {
+    @Override
+    public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+    {
+    }
+  }
+
+  static class Foo implements HotLoopCallee
+  {
+    @Override
+    public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+    {
+      inspector.visit("flag1", true);
+      inspector.visit("flag2", false);
+      inspector.visit("key", "value");
+      inspector.visit("empty", new Empty());
+      inspector.visit("object", ByteBuffer.allocate(1));
+      inspector.visit("array", new Set[] {new HashSet(), new TreeSet()});
+      inspector.visit("emptyArray", new Set[] {});
+    }
+  }
+
+  static class Bar implements HotLoopCallee
+  {
+    @Override
+    public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+    {
+      inspector.visit("foo", new Foo());
+      inspector.visit("array", new Foo[] {new Foo(), new Foo()});
+    }
+  }
+
+  @Test
+  public void testStringRuntimeShape()
+  {
+    String barRuntimeShape = StringRuntimeShape.of(new Bar());
+    Assert.assertEquals(
+        "io.druid.query.monomorphicprocessing.StringRuntimeShapeTest$Bar {\n"
+        + "  foo: io.druid.query.monomorphicprocessing.StringRuntimeShapeTest$Foo {\n"
+        + "    flag1: true,\n"
+        + "    flag2: false,\n"
+        + "    key: value,\n"
+        + "    empty: io.druid.query.monomorphicprocessing.StringRuntimeShapeTest$Empty,\n"
+        + "    object: java.nio.HeapByteBuffer {order: BIG_ENDIAN},\n"
+        + "    array: [\n"
+        + "      java.util.HashSet,\n"
+        + "      java.util.TreeSet\n"
+        + "    ],\n"
+        + "    emptyArray: []\n"
+        + "  },\n"
+        + "  array: [\n"
+        + "    io.druid.query.monomorphicprocessing.StringRuntimeShapeTest$Foo {\n"
+        + "      flag1: true,\n"
+        + "      flag2: false,\n"
+        + "      key: value,\n"
+        + "      empty: io.druid.query.monomorphicprocessing.StringRuntimeShapeTest$Empty,\n"
+        + "      object: java.nio.HeapByteBuffer {order: BIG_ENDIAN},\n"
+        + "      array: [\n"
+        + "        java.util.HashSet,\n"
+        + "        java.util.TreeSet\n"
+        + "      ],\n"
+        + "      emptyArray: []\n"
+        + "    },\n"
+        + "    io.druid.query.monomorphicprocessing.StringRuntimeShapeTest$Foo {\n"
+        + "      flag1: true,\n"
+        + "      flag2: false,\n"
+        + "      key: value,\n"
+        + "      empty: io.druid.query.monomorphicprocessing.StringRuntimeShapeTest$Empty,\n"
+        + "      object: java.nio.HeapByteBuffer {order: BIG_ENDIAN},\n"
+        + "      array: [\n"
+        + "        java.util.HashSet,\n"
+        + "        java.util.TreeSet\n"
+        + "      ],\n"
+        + "      emptyArray: []\n"
+        + "    }\n"
+        + "  ]\n"
+        + "}",
+        barRuntimeShape
+    );
+  }
+}

processing/src/test/java/io/druid/query/topn/TopNQueryRunnerTest.java

@@ -45,6 +45,7 @@ import io.druid.query.QueryRunnerTestHelper;
 import io.druid.query.Result;
 import io.druid.query.TestQueryRunners;
 import io.druid.query.aggregation.AggregatorFactory;
+import io.druid.query.aggregation.CountAggregatorFactory;
 import io.druid.query.aggregation.DoubleMaxAggregatorFactory;
 import io.druid.query.aggregation.DoubleMinAggregatorFactory;
 import io.druid.query.aggregation.DoubleSumAggregatorFactory;
@@ -107,6 +108,23 @@ public class TopNQueryRunnerTest
 {
   @Parameterized.Parameters(name="{0}")
   public static Iterable<Object[]> constructorFeeder() throws IOException
+  {
+    List<QueryRunner<Result<TopNResultValue>>> retVal = queryRunners();
+    List<Object[]> parameters = new ArrayList<>();
+    for (int i = 0; i < 8; i++) {
+      for (QueryRunner<Result<TopNResultValue>> firstParameter : retVal) {
+        Object[] params = new Object[4];
+        params[0] = firstParameter;
+        params[1] = (i & 1) != 0;
+        params[2] = (i & 2) != 0;
+        params[3] = (i & 4) != 0;
+        parameters.add(params);
+      }
+    }
+    return parameters;
+  }
+
+  public static List<QueryRunner<Result<TopNResultValue>>> queryRunners() throws IOException
   {
     List<QueryRunner<Result<TopNResultValue>>> retVal = Lists.newArrayList();
     retVal.addAll(
@@ -143,20 +161,53 @@ public class TopNQueryRunnerTest
             )
         )
     );
-
-    return QueryRunnerTestHelper.transformToConstructionFeeder(retVal);
+    return retVal;
   }
 
   private final QueryRunner<Result<TopNResultValue>> runner;
+  private final boolean duplicateSingleAggregatorQueries;
 
   @Rule
   public ExpectedException expectedException = ExpectedException.none();
 
   public TopNQueryRunnerTest(
-      QueryRunner<Result<TopNResultValue>> runner
+      QueryRunner<Result<TopNResultValue>> runner,
+      boolean specializeGeneric1AggPooledTopN,
+      boolean specializeGeneric2AggPooledTopN,
+      boolean duplicateSingleAggregatorQueries
   )
   {
     this.runner = runner;
+    PooledTopNAlgorithm.specializeGeneric1AggPooledTopN = specializeGeneric1AggPooledTopN;
+    PooledTopNAlgorithm.specializeGeneric2AggPooledTopN = specializeGeneric2AggPooledTopN;
+    this.duplicateSingleAggregatorQueries = duplicateSingleAggregatorQueries;
+  }
+
+  private List<AggregatorFactory> duplicateAggregators(AggregatorFactory aggregatorFactory, AggregatorFactory duplicate)
+  {
+    if (duplicateSingleAggregatorQueries) {
+      return ImmutableList.of(aggregatorFactory, duplicate);
+    } else {
+      return Collections.singletonList(aggregatorFactory);
+    }
+  }
+
+  private List<Map<String, Object>> withDuplicateResults(
+      List<? extends Map<String, Object>> results,
+      String key,
+      String duplicateKey
+  )
+  {
+    if (!duplicateSingleAggregatorQueries) {
+      return (List<Map<String, Object>>) results;
+    }
+    List<Map<String, Object>> resultsWithDuplicates = new ArrayList<>();
+    for (Map<String, Object> result : results) {
+      resultsWithDuplicates.add(
+          ImmutableMap.<String, Object>builder().putAll(result).put(duplicateKey, result.get(key)).build()
+      );
+    }
+    return resultsWithDuplicates;
   }
 
   private Sequence<Result<TopNResultValue>> assertExpectedResults(
@@ -2992,6 +3043,10 @@ public class TopNQueryRunnerTest
   @Test
   public void testTopNQueryByComplexMetric()
   {
+    ImmutableList<DimensionSpec> aggregatorDimensionSpecs = ImmutableList.<DimensionSpec>of(new DefaultDimensionSpec(
+        QueryRunnerTestHelper.qualityDimension,
+        QueryRunnerTestHelper.qualityDimension
+    ));
     TopNQuery query =
         new TopNQueryBuilder()
             .dataSource(QueryRunnerTestHelper.dataSource)
@@ -3000,24 +3055,17 @@ public class TopNQueryRunnerTest
             .metric(new NumericTopNMetricSpec("numVals"))
             .threshold(10)
             .intervals(QueryRunnerTestHelper.firstToThird)
-            .aggregators(
-                Lists.<AggregatorFactory>newArrayList(
-                    new CardinalityAggregatorFactory(
-                        "numVals",
-                        ImmutableList.<DimensionSpec>of(new DefaultDimensionSpec(
-                            QueryRunnerTestHelper.qualityDimension,
-                            QueryRunnerTestHelper.qualityDimension
-                        )),
-                        false
-                    )
-                )
-            )
+            .aggregators(duplicateAggregators(
+                new CardinalityAggregatorFactory("numVals", aggregatorDimensionSpecs, false),
+                new CardinalityAggregatorFactory("numVals1", aggregatorDimensionSpecs, false)
+            ))
             .build();
 
-    List<Result<TopNResultValue>> expectedResults = Arrays.asList(
+    List<Result<TopNResultValue>> expectedResults = Collections.singletonList(
         new Result<>(
             new DateTime("2011-04-01T00:00:00.000Z"),
             new TopNResultValue(
+                withDuplicateResults(
                     Arrays.<Map<String, Object>>asList(
                         ImmutableMap.<String, Object>of(
                             "market", "spot",
@@ -3031,6 +3079,9 @@ public class TopNQueryRunnerTest
                             "market", "upfront",
                             "numVals", 2.000977198748901d
                         )
+                    ),
+                    "numVals",
+                    "numVals1"
                 )
             )
         )
@@ -3048,6 +3099,11 @@ public class TopNQueryRunnerTest
                                                         QueryRunnerTestHelper.marketDimension,
                                                         helloFn);
 
+    ImmutableList<DimensionSpec> aggregatorDimensionSpecs = ImmutableList.<DimensionSpec>of(new ExtractionDimensionSpec(
+        QueryRunnerTestHelper.qualityDimension,
+        QueryRunnerTestHelper.qualityDimension,
+        helloFn
+    ));
     TopNQuery query =
         new TopNQueryBuilder()
             .dataSource(QueryRunnerTestHelper.dataSource)
@@ -3056,30 +3112,25 @@ public class TopNQueryRunnerTest
             .metric(new NumericTopNMetricSpec("numVals"))
             .threshold(10)
             .intervals(QueryRunnerTestHelper.firstToThird)
-            .aggregators(
-                Lists.<AggregatorFactory>newArrayList(
-                    new CardinalityAggregatorFactory(
-                        "numVals",
-                        ImmutableList.<DimensionSpec>of(new ExtractionDimensionSpec(
-                            QueryRunnerTestHelper.qualityDimension,
-                            QueryRunnerTestHelper.qualityDimension,
-                            helloFn
-                        )),
-                        false
-                    )
-                )
-            )
+            .aggregators(duplicateAggregators(
+                new CardinalityAggregatorFactory("numVals", aggregatorDimensionSpecs,false),
+                new CardinalityAggregatorFactory("numVals1",aggregatorDimensionSpecs,false)
+            ))
             .build();
 
-    List<Result<TopNResultValue>> expectedResults = Arrays.asList(
+    List<Result<TopNResultValue>> expectedResults = Collections.singletonList(
         new Result<>(
             new DateTime("2011-04-01T00:00:00.000Z"),
             new TopNResultValue(
-                Arrays.<Map<String, Object>>asList(
+                withDuplicateResults(
+                    Collections.singletonList(
                         ImmutableMap.<String, Object>of(
                             "market", "hello",
                             "numVals", 1.0002442201269182d
                         )
+                    ),
+                    "numVals",
+                    "numVals1"
                 )
             )
         )
@@ -3567,12 +3618,16 @@ public class TopNQueryRunnerTest
         .metric(new DimensionTopNMetricSpec(null, StringComparators.ALPHANUMERIC))
         .threshold(2)
         .intervals(QueryRunnerTestHelper.secondOnly)
-        .aggregators(Lists.<AggregatorFactory>newArrayList(QueryRunnerTestHelper.rowsCount))
+        .aggregators(duplicateAggregators(
+            QueryRunnerTestHelper.rowsCount,
+            new CountAggregatorFactory("rows1")
+        ))
         .build();
     List<Result<TopNResultValue>> expectedResults = Arrays.asList(
         new Result<>(
             new DateTime("2011-04-02T00:00:00.000Z"),
             new TopNResultValue(
+                withDuplicateResults(
                     Arrays.asList(
                         ImmutableMap.<String, Object>of(
                             "market", "spot",
@@ -3582,6 +3637,9 @@ public class TopNQueryRunnerTest
                             "market", "total_market",
                             "rows", 2L
                         )
+                    ),
+                    "rows",
+                    "rows1"
                 )
             )
         )
@@ -3599,12 +3657,16 @@ public class TopNQueryRunnerTest
         .metric(new DimensionTopNMetricSpec(null, StringComparators.NUMERIC))
         .threshold(2)
         .intervals(QueryRunnerTestHelper.secondOnly)
-        .aggregators(Lists.<AggregatorFactory>newArrayList(QueryRunnerTestHelper.rowsCount))
+        .aggregators(duplicateAggregators(
+            QueryRunnerTestHelper.rowsCount,
+            new CountAggregatorFactory("rows1")
+        ))
         .build();
     List<Result<TopNResultValue>> expectedResults = Arrays.asList(
         new Result<>(
             new DateTime("2011-04-02T00:00:00.000Z"),
             new TopNResultValue(
+                withDuplicateResults(
                     Arrays.asList(
                         ImmutableMap.<String, Object>of(
                             "market", "spot",
@@ -3614,6 +3676,9 @@ public class TopNQueryRunnerTest
                             "market", "total_market",
                             "rows", 2L
                         )
+                    ),
+                    "rows",
+                    "rows1"
                 )
             )
         )

processing/src/test/java/io/druid/segment/BitmapOffsetTest.java

@@ -26,6 +26,7 @@ import com.google.common.collect.Sets;
 import io.druid.collections.bitmap.BitSetBitmapFactory;
 import io.druid.collections.bitmap.BitmapFactory;
 import io.druid.collections.bitmap.ConciseBitmapFactory;
+import io.druid.collections.bitmap.ImmutableBitmap;
 import io.druid.collections.bitmap.MutableBitmap;
 import io.druid.collections.bitmap.RoaringBitmapFactory;
 import io.druid.segment.data.Offset;
@@ -81,7 +82,8 @@ public class BitmapOffsetTest
       mutable.add(val);
     }
 
-    final BitmapOffset offset = new BitmapOffset(factory, factory.makeImmutableBitmap(mutable), descending);
+    ImmutableBitmap bitmap = factory.makeImmutableBitmap(mutable);
+    final BitmapOffset offset = BitmapOffset.of(bitmap, descending, bitmap.size());
     final int[] expected = descending ? TEST_VALS_FLIP : TEST_VALS;
 
     int count = 0;