segment interface refactor for proposal 2965 (#2990)

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

@@ -0,0 +1,33 @@
+/*
+ * 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.segment;
+
+public abstract class AbstractSegment implements Segment
+{
+  @Override
+  public <T> T as(Class<T> clazz)
+  {
+    if (clazz.equals(QueryableIndex.class)) {
+      return (T) asQueryableIndex();
+    } else if (clazz.equals(StorageAdapter.class)) {
+      return (T) asStorageAdapter();
+    }
+    return null;
+  }
+}

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

@@ -21,13 +21,14 @@ package io.druid.segment;
 
 import io.druid.segment.incremental.IncrementalIndex;
 import io.druid.segment.incremental.IncrementalIndexStorageAdapter;
+
 import org.joda.time.Interval;
 
 import java.io.IOException;
 
 /**
  */
-public class IncrementalIndexSegment implements Segment
+public class IncrementalIndexSegment extends AbstractSegment
 {
   private final IncrementalIndex index;
   private final String segmentIdentifier;

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

@@ -25,7 +25,7 @@ import java.io.IOException;
 
 /**
 */
-public class QueryableIndexSegment implements Segment
+public class QueryableIndexSegment extends AbstractSegment
 {
   private final QueryableIndex index;
   private final String identifier;

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

@@ -20,13 +20,14 @@
 package io.druid.segment;
 
 import com.metamx.emitter.EmittingLogger;
+
 import org.joda.time.Interval;
 
 import java.io.Closeable;
 import java.io.IOException;
 import java.util.concurrent.atomic.AtomicBoolean;
 
-public class ReferenceCountingSegment implements Segment
+public class ReferenceCountingSegment extends AbstractSegment
 {
   private static final EmittingLogger log = new EmittingLogger(ReferenceCountingSegment.class);
 

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

@@ -31,4 +31,23 @@ public interface Segment extends Closeable
   public Interval getDataInterval();
   public QueryableIndex asQueryableIndex();
   public StorageAdapter asStorageAdapter();
+  
+  /**
+   * Request an implementation of a particular interface.
+   *
+   * If the passed-in interface is {@link QueryableIndex} or {@link StorageAdapter}, then this method behaves
+   * identically to {@link #asQueryableIndex()} or {@link #asStorageAdapter()}. Other interfaces are only
+   * expected to be requested by callers that have specific knowledge of extra features provided by specific
+   * segment types. For example, an extension might provide a custom Segment type that can offer both
+   * StorageAdapter and some new interface. That extension can also offer a Query that uses that new interface.
+   * 
+   * Implementations which accept classes other than {@link QueryableIndex} or {@link StorageAdapter} are limited 
+   * to using those classes within the extension. This means that one extension cannot rely on the `Segment.as` 
+   * behavior of another extension.
+   *
+   * @param clazz desired interface
+   * @param <T> desired interface
+   * @return instance of clazz, or null if the interface is not supported by this segment
+   */
+  public <T> T as(Class<T> clazz);
 }

processing/src/test/java/io/druid/query/MultiValuedDimensionTest.java

@@ -28,6 +28,7 @@ import com.google.common.collect.Maps;
 import com.google.common.io.Files;
 import com.metamx.common.guava.Sequence;
 import com.metamx.common.guava.Sequences;
+
 import io.druid.data.input.Row;
 import io.druid.data.input.impl.CSVParseSpec;
 import io.druid.data.input.impl.DimensionsSpec;
@@ -55,9 +56,11 @@ import io.druid.segment.IncrementalIndexSegment;
 import io.druid.segment.IndexSpec;
 import io.druid.segment.QueryableIndex;
 import io.druid.segment.QueryableIndexSegment;
+import io.druid.segment.Segment;
 import io.druid.segment.TestHelper;
 import io.druid.segment.incremental.IncrementalIndex;
 import io.druid.segment.incremental.OnheapIncrementalIndex;
+
 import org.apache.commons.io.FileUtils;
 import org.joda.time.DateTime;
 import org.junit.AfterClass;
@@ -150,7 +153,7 @@ public class MultiValuedDimensionTest
         .build();
 
     Sequence<Row> result = helper.runQueryOnSegmentsObjs(
-        ImmutableList.of(
+        ImmutableList.<Segment>of(
             new QueryableIndexSegment("sid1", queryableIndex),
             new IncrementalIndexSegment(incrementalIndex, "sid2")
         ),
@@ -170,7 +173,7 @@ public class MultiValuedDimensionTest
     TestHelper.assertExpectedObjects(expectedResults, Sequences.toList(result, new ArrayList<Row>()), "");
 
     result = helper.runQueryOnSegmentsObjs(
-        ImmutableList.of(
+        ImmutableList.<Segment>of(
             new QueryableIndexSegment("sid1", queryableIndex),
             new IncrementalIndexSegment(incrementalIndex, "sid2")
         ),
@@ -201,7 +204,7 @@ public class MultiValuedDimensionTest
         .build();
 
     Sequence<Row> result = helper.runQueryOnSegmentsObjs(
-        ImmutableList.of(
+        ImmutableList.<Segment>of(
             new QueryableIndexSegment("sid1", queryableIndex),
             new IncrementalIndexSegment(incrementalIndex, "sid2")
         ),
@@ -249,7 +252,7 @@ public class MultiValuedDimensionTest
         .build();
 
     Sequence<Row> result = helper.runQueryOnSegmentsObjs(
-        ImmutableList.of(
+        ImmutableList.<Segment>of(
             new QueryableIndexSegment("sid1", queryableIndex),
             new IncrementalIndexSegment(incrementalIndex, "sid2")
         ),

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

@@ -41,6 +41,7 @@ import com.metamx.common.guava.Sequence;
 import com.metamx.common.guava.Sequences;
 import com.metamx.common.guava.Yielder;
 import com.metamx.common.guava.YieldingAccumulator;
+
 import io.druid.collections.StupidPool;
 import io.druid.data.input.Row;
 import io.druid.data.input.impl.InputRowParser;
@@ -63,6 +64,7 @@ import io.druid.query.groupby.GroupByQueryRunnerFactory;
 import io.druid.query.select.SelectQueryEngine;
 import io.druid.query.select.SelectQueryQueryToolChest;
 import io.druid.query.select.SelectQueryRunnerFactory;
+import io.druid.segment.AbstractSegment;
 import io.druid.segment.IndexIO;
 import io.druid.segment.IndexMerger;
 import io.druid.segment.IndexSpec;
@@ -72,6 +74,7 @@ import io.druid.segment.Segment;
 import io.druid.segment.column.ColumnConfig;
 import io.druid.segment.incremental.IncrementalIndex;
 import io.druid.segment.incremental.OnheapIncrementalIndex;
+
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.io.LineIterator;
 import org.junit.rules.TemporaryFolder;

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

@@ -43,7 +43,7 @@ public class ReferenceCountingSegmentTest
   public void setUp() throws Exception
   {
     segment = new ReferenceCountingSegment(
-        new Segment()
+        new AbstractSegment()
         {
           @Override
           public String getIdentifier()

server/src/test/java/io/druid/segment/loading/CacheTestSegmentLoader.java

@@ -20,10 +20,13 @@
 package io.druid.segment.loading;
 
 import com.metamx.common.MapUtils;
+
+import io.druid.segment.AbstractSegment;
 import io.druid.segment.QueryableIndex;
 import io.druid.segment.Segment;
 import io.druid.segment.StorageAdapter;
 import io.druid.timeline.DataSegment;
+
 import org.joda.time.Interval;
 
 import java.io.File;
@@ -49,7 +52,7 @@ public class CacheTestSegmentLoader implements SegmentLoader
   @Override
   public Segment getSegment(final DataSegment segment) throws SegmentLoadingException
   {
-    return new Segment()
+    return new AbstractSegment()
     {
       @Override
       public String getIdentifier()

server/src/test/java/io/druid/server/coordination/ServerManagerTest.java

@@ -37,10 +37,11 @@ import com.metamx.common.guava.YieldingAccumulator;
 import com.metamx.common.guava.YieldingSequenceBase;
 import com.metamx.emitter.EmittingLogger;
 import com.metamx.emitter.service.ServiceMetricEvent;
+
 import io.druid.client.cache.CacheConfig;
 import io.druid.client.cache.LocalCacheProvider;
-import io.druid.granularity.QueryGranularity;
 import io.druid.granularity.QueryGranularities;
+import io.druid.granularity.QueryGranularity;
 import io.druid.jackson.DefaultObjectMapper;
 import io.druid.query.ConcatQueryRunner;
 import io.druid.query.Druids;
@@ -54,6 +55,7 @@ import io.druid.query.Result;
 import io.druid.query.aggregation.MetricManipulationFn;
 import io.druid.query.search.SearchResultValue;
 import io.druid.query.search.search.SearchQuery;
+import io.druid.segment.AbstractSegment;
 import io.druid.segment.IndexIO;
 import io.druid.segment.QueryableIndex;
 import io.druid.segment.ReferenceCountingSegment;
@@ -64,6 +66,7 @@ import io.druid.segment.loading.SegmentLoadingException;
 import io.druid.server.metrics.NoopServiceEmitter;
 import io.druid.timeline.DataSegment;
 import io.druid.timeline.partition.NoneShardSpec;
+
 import org.joda.time.Interval;
 import org.junit.Assert;
 import org.junit.Before;
@@ -592,7 +595,7 @@ public class ServerManagerTest
     }
   }
 
-  private static class SegmentForTesting implements Segment
+  private static class SegmentForTesting extends AbstractSegment
   {
     private final String version;
     private final Interval interval;