Fix dimension selectors with extractionFns on missing columns.

extensions-contrib/virtual-columns/src/main/java/io/druid/segment/MapVirtualColumn.java

@@ -165,25 +165,25 @@ public String get()
   public DimensionSelector makeDimensionSelector(DimensionSpec dimensionSpec, ColumnSelectorFactory factory)
   {
     // Could probably do something useful here if the column name is dot-style. But for now just return nothing.
-    return null;
+    return dimensionSpec.decorate(DimensionSelectorUtils.constantSelector(null, dimensionSpec.getExtractionFn()));
   }
 
   @Override
   public FloatColumnSelector makeFloatColumnSelector(String columnName, ColumnSelectorFactory factory)
   {
-    return null;
+    return ZeroFloatColumnSelector.instance();
   }
 
   @Override
   public LongColumnSelector makeLongColumnSelector(String columnName, ColumnSelectorFactory factory)
   {
-    return null;
+    return ZeroLongColumnSelector.instance();
   }
 
   @Override
   public DoubleColumnSelector makeDoubleColumnSelector(String columnName, ColumnSelectorFactory factory)
   {
-    return null;
+    return ZeroDoubleColumnSelector.instance();
   }
 
   @Override

processing/src/main/java/io/druid/query/search/SearchQueryRunner.java

@@ -44,7 +44,6 @@
 import io.druid.segment.DoubleColumnSelector;
 import io.druid.segment.FloatColumnSelector;
 import io.druid.segment.LongColumnSelector;
-import io.druid.segment.NullDimensionSelector;
 import io.druid.segment.Segment;
 import io.druid.segment.column.ColumnCapabilities;
 import io.druid.segment.column.ValueType;
@@ -132,7 +131,7 @@ public void updateSearchResultSet(
         final Object2IntRBTreeMap<SearchHit> set
     )
     {
-      if (selector != null && !(selector instanceof NullDimensionSelector)) {
+      if (selector != null && !isNilSelector(selector)) {
         final IndexedInts vals = selector.getRow();
         for (int i = 0; i < vals.size(); ++i) {
           final String dimVal = selector.lookupName(vals.get(i));
@@ -147,6 +146,13 @@ public void updateSearchResultSet(
     }
   }
 
+  private static boolean isNilSelector(final DimensionSelector selector)
+  {
+    return selector.nameLookupPossibleInAdvance()
+           && selector.getValueCardinality() == 1
+           && selector.lookupName(0) == null;
+  }
+
   public static class LongSearchColumnSelectorStrategy implements SearchColumnSelectorStrategy<LongColumnSelector>
   {
     @Override

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

@@ -0,0 +1,121 @@
+/*
+ * 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;
+
+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;
+import io.druid.segment.historical.SingleValueHistoricalDimensionSelector;
+
+import javax.annotation.Nullable;
+import java.util.Objects;
+
+public class ConstantDimensionSelector implements SingleValueHistoricalDimensionSelector, IdLookup
+{
+  private final String value;
+
+  public ConstantDimensionSelector(final String value)
+  {
+    if (Strings.isNullOrEmpty(value)) {
+      // There's an optimized implementation for nulls that callers should use instead.
+      throw new IllegalArgumentException("Use NullDimensionSelector or DimensionSelectorUtils.constantSelector");
+    }
+
+    this.value = value;
+  }
+
+  @Override
+  public IndexedInts getRow()
+  {
+    return ZeroIndexedInts.instance();
+  }
+
+  @Override
+  public int getRowValue()
+  {
+    return 0;
+  }
+
+  @Override
+  public int getRowValue(int offset)
+  {
+    return 0;
+  }
+
+  @Override
+  public IndexedInts getRow(int offset)
+  {
+    return getRow();
+  }
+
+  @Override
+  public ValueMatcher makeValueMatcher(String matchValue)
+  {
+    return BooleanValueMatcher.of(Objects.equals(value, matchValue));
+  }
+
+  @Override
+  public ValueMatcher makeValueMatcher(Predicate<String> predicate)
+  {
+    return BooleanValueMatcher.of(predicate.apply(value));
+  }
+
+  @Override
+  public int getValueCardinality()
+  {
+    return 1;
+  }
+
+  @Override
+  public String lookupName(int id)
+  {
+    assert id == 0 : "id = " + id;
+    return value;
+  }
+
+  @Override
+  public boolean nameLookupPossibleInAdvance()
+  {
+    return true;
+  }
+
+  @Nullable
+  @Override
+  public IdLookup idLookup()
+  {
+    return this;
+  }
+
+  @Override
+  public int lookupId(String name)
+  {
+    return value.equals(name) ? 0 : -1;
+  }
+
+  @Override
+  public void inspectRuntimeShape(RuntimeShapeInspector inspector)
+  {
+    inspector.visit("value", value);
+  }
+}

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

@@ -21,12 +21,15 @@
 
 import com.google.common.base.Predicate;
 import com.google.common.base.Predicates;
+import com.google.common.base.Strings;
 import io.druid.java.util.common.IAE;
+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.filter.BooleanValueMatcher;
 
+import javax.annotation.Nullable;
 import java.util.BitSet;
 import java.util.Objects;
 
@@ -246,4 +249,25 @@ public static BitSet makePredicateMatchingSet(DimensionSelector selector, Predic
     }
     return valueIds;
   }
+
+  public static DimensionSelector constantSelector(@Nullable final String value)
+  {
+    if (Strings.isNullOrEmpty(value)) {
+      return NullDimensionSelector.instance();
+    } else {
+      return new ConstantDimensionSelector(value);
+    }
+  }
+
+  public static DimensionSelector constantSelector(
+      @Nullable final String value,
+      @Nullable final ExtractionFn extractionFn
+  )
+  {
+    if (extractionFn == null) {
+      return constantSelector(value);
+    } else {
+      return constantSelector(extractionFn.apply(value));
+    }
+  }
 }

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

@@ -404,7 +404,10 @@ public Sequence<Cursor> build()
                 public Cursor apply(final Interval inputInterval)
                 {
                   final long timeStart = Math.max(interval.getStartMillis(), inputInterval.getStartMillis());
-                  final long timeEnd = Math.min(interval.getEndMillis(), gran.increment(inputInterval.getStart()).getMillis());
+                  final long timeEnd = Math.min(
+                      interval.getEndMillis(),
+                      gran.increment(inputInterval.getStart()).getMillis()
+                  );
 
                   if (descending) {
                     for (; baseOffset.withinBounds(); baseOffset.increment()) {
@@ -503,7 +506,7 @@ private DimensionSelector makeDimensionSelectorUndecorated(
 
                       final Column columnDesc = index.getColumn(dimension);
                       if (columnDesc == null) {
-                        return NullDimensionSelector.instance();
+                        return DimensionSelectorUtils.constantSelector(null, extractionFn);
                       }
 
                       if (dimension.equals(Column.TIME_COLUMN_NAME)) {
@@ -534,7 +537,7 @@ private DimensionSelector makeDimensionSelectorUndecorated(
 
                       final DictionaryEncodedColumn<String> column = cachedColumn;
                       if (column == null) {
-                        return NullDimensionSelector.instance();
+                        return DimensionSelectorUtils.constantSelector(null, extractionFn);
                       } else {
                         return column.makeDimensionSelector(this, extractionFn);
                       }
@@ -883,7 +886,7 @@ public void reset()
                     return new QueryableIndexBaseCursor<FilteredOffset>()
                     {
                       private Offset baseOffset;
-                      
+
                       {
                         cursorOffset = new FilteredOffset(this, descending, postFilter, bitmapIndexSelector);
                         reset();

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

@@ -26,7 +26,6 @@
 import io.druid.segment.column.ColumnCapabilities;
 import io.druid.segment.virtual.ExpressionVirtualColumn;
 
-import javax.annotation.Nullable;
 import java.util.List;
 
 /**
@@ -69,9 +68,8 @@ public interface VirtualColumn extends Cacheable
    * @param dimensionSpec the dimensionSpec this column was referenced with
    * @param factory       column selector factory
    *
-   * @return the selector, or null if we can't make a selector
+   * @return the selector, must not be null
    */
-  @Nullable
   DimensionSelector makeDimensionSelector(DimensionSpec dimensionSpec, ColumnSelectorFactory factory);
 
   /**
@@ -81,9 +79,8 @@ public interface VirtualColumn extends Cacheable
    * @param columnName the name this virtual column was referenced with
    * @param factory    column selector factory
    *
-   * @return the selector, or null if we can't make a selector
+   * @return the selector, must not be null
    */
-  @Nullable
   FloatColumnSelector makeFloatColumnSelector(String columnName, ColumnSelectorFactory factory);
 
   /**
@@ -93,9 +90,8 @@ public interface VirtualColumn extends Cacheable
    * @param columnName the name this virtual column was referenced with
    * @param factory    column selector factory
    *
-   * @return the selector, or null if we can't make a selector
+   * @return the selector, must not be null
    */
-  @Nullable
   LongColumnSelector makeLongColumnSelector(String columnName, ColumnSelectorFactory factory);
 
   /**
@@ -105,9 +101,8 @@ public interface VirtualColumn extends Cacheable
    * @param columnName the name this virtual column was referenced with
    * @param factory    column selector factory
    *
-   * @return the selector, or null if we can't make a selector
+   * @return the selector, must not be null
    */
-  @Nullable
   DoubleColumnSelector makeDoubleColumnSelector(String columnName, ColumnSelectorFactory factory);
 
   /**