Fix empty results on ExtractionFilter.

* Now returns empty results rather than erroring out
* Added unit tests for multiples case

processing/src/main/java/io/druid/segment/filter/ExtractionFilter.java

@@ -19,6 +19,7 @@ package io.druid.segment.filter;
 
 import com.google.common.collect.Lists;
 import com.metamx.collections.bitmap.ImmutableBitmap;
+import com.metamx.collections.bitmap.WrappedConciseBitmap;
 import io.druid.query.extraction.DimExtractionFn;
 import io.druid.query.filter.BitmapIndexSelector;
 import io.druid.query.filter.Filter;
@@ -52,13 +53,14 @@ public class ExtractionFilter implements Filter
   {
     final Indexed<String> allDimVals = selector.getDimensionValues(dimension);
     final List<Filter> filters = Lists.newArrayList();
-
+    if (allDimVals != null) {
       for (int i = 0; i < allDimVals.size(); i++) {
         String dimVal = allDimVals.get(i);
         if (value.equals(fn.apply(dimVal))) {
           filters.add(new SelectorFilter(dimension, dimVal));
         }
       }
+    }
 
     return filters;
   }
@@ -66,6 +68,10 @@ public class ExtractionFilter implements Filter
   @Override
   public ImmutableBitmap getBitmapIndex(BitmapIndexSelector selector)
   {
+    final List<Filter> filters = makeFilters(selector);
+    if (filters.isEmpty()) {
+      return new WrappedConciseBitmap();
+    }
     return new OrFilter(makeFilters(selector)).getBitmapIndex(selector);
   }
 

processing/src/test/java/io/druid/segment/filter/ExtractionDimFilterTest.java

@@ -0,0 +1,145 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright 2012 - 2015 Metamarkets Group Inc.
+ *
+ * Licensed 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.filter;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.metamx.collections.bitmap.BitmapFactory;
+import com.metamx.collections.bitmap.ConciseBitmapFactory;
+import com.metamx.collections.bitmap.ImmutableBitmap;
+import com.metamx.collections.bitmap.WrappedConciseBitmap;
+import com.metamx.collections.spatial.ImmutableRTree;
+import io.druid.query.extraction.DimExtractionFn;
+import io.druid.query.filter.BitmapIndexSelector;
+import io.druid.query.filter.Filter;
+import io.druid.segment.data.ArrayIndexed;
+import io.druid.segment.data.Indexed;
+import it.uniroma3.mat.extendedset.intset.ConciseSet;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+import java.util.Collection;
+import java.util.Map;
+
+/**
+ *
+ */
+public class ExtractionDimFilterTest
+{
+  private static final Map<String, String[]> DIM_VALS = ImmutableMap.<String, String[]>of(
+      "foo", new String[]{"foo1","foo2","foo3"},
+      "bar", new String[]{"bar1"},
+      "baz", new String[]{"foo1"}
+  );
+
+  private static final Map<String, String> EXTRACTION_VALUES = ImmutableMap.of(
+      "foo1","extractDimVal"
+  );
+
+  private static ImmutableBitmap foo1BitMap;
+  @BeforeClass
+  public static void setupStatic(){
+    final ConciseSet conciseSet = new ConciseSet();
+    conciseSet.add(1);
+    foo1BitMap = new WrappedConciseBitmap(conciseSet);
+  }
+  private static final BitmapIndexSelector BITMAP_INDEX_SELECTOR = new BitmapIndexSelector()
+  {
+    @Override
+    public Indexed<String> getDimensionValues(String dimension)
+    {
+      final String[] vals = DIM_VALS.get(dimension);
+      return vals == null ? null : new ArrayIndexed<String>(vals, String.class);
+    }
+
+    @Override
+    public int getNumRows()
+    {
+      return 1;
+    }
+
+    @Override
+    public BitmapFactory getBitmapFactory()
+    {
+      return new ConciseBitmapFactory();
+    }
+
+    @Override
+    public ImmutableBitmap getBitmapIndex(String dimension, String value)
+    {
+      return "foo1".equals(value) ? foo1BitMap : null;
+    }
+
+    @Override
+    public ImmutableRTree getSpatialIndex(String dimension)
+    {
+      return null;
+    }
+  };
+  private static final DimExtractionFn DIM_EXTRACTION_FN = new DimExtractionFn()
+  {
+    @Override
+    public byte[] getCacheKey()
+    {
+      return new byte[0];
+    }
+
+    @Override
+    public String apply(String dimValue)
+    {
+      final String retval = EXTRACTION_VALUES.get(dimValue);
+      return retval == null ? dimValue : retval;
+    }
+
+    @Override
+    public boolean preservesOrdering()
+    {
+      return false;
+    }
+  };
+
+  @Test
+  public void testEmpty(){
+    ExtractionFilter extractionFilter = new ExtractionFilter(
+        "foo", "NFDJUKFNDSJFNS", DIM_EXTRACTION_FN
+    );
+    ImmutableBitmap immutableBitmap = extractionFilter.getBitmapIndex(BITMAP_INDEX_SELECTOR);
+    Assert.assertEquals(0, immutableBitmap.size());
+  }
+
+  @Test
+  public void testNull(){
+    ExtractionFilter extractionFilter = new ExtractionFilter(
+        "FDHJSFFHDS", "extractDimVal", DIM_EXTRACTION_FN
+    );
+    ImmutableBitmap immutableBitmap = extractionFilter.getBitmapIndex(BITMAP_INDEX_SELECTOR);
+    Assert.assertEquals(0, immutableBitmap.size());
+  }
+
+  @Test
+  public void testNormal(){
+    ExtractionFilter extractionFilter = new ExtractionFilter(
+        "foo", "extractDimVal", DIM_EXTRACTION_FN
+    );
+    ImmutableBitmap immutableBitmap = extractionFilter.getBitmapIndex(BITMAP_INDEX_SELECTOR);
+    Assert.assertEquals(1, immutableBitmap.size());
+  }
+}