[GitHub] [druid] abhishekagarwal87 commented on a change in pull request #10518: Add grouping_id function

[GitBox <gi...@apache.org>]

abhishekagarwal87 commented on a change in pull request #10518:
URL: https://github.com/apache/druid/pull/10518#discussion_r515945767



##########
File path: processing/src/main/java/org/apache/druid/query/groupby/epinephelinae/RowBasedGrouperHelper.java
##########
@@ -576,7 +594,12 @@ private static ValueExtractFunction makeValueExtractFunction(
           // Add aggregations.
           final int resultRowAggregatorStart = query.getResultRowAggregatorStart();
           for (int i = 0; i < entry.getValues().length; i++) {
-            resultRow.set(resultRowAggregatorStart + i, entry.getValues()[i]);
+            if (dimsToInclude != null && groupingAggregatorsBitSet.get(i)) {

Review comment:
       Right. This is one change I am a bit anxious about. is there any existing benchmark I could use? 

##########
File path: processing/src/main/java/org/apache/druid/query/aggregation/GroupingAggregatorFactory.java
##########
@@ -0,0 +1,282 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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 org.apache.druid.query.aggregation;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Preconditions;
+import org.apache.druid.annotations.EverythingIsNonnullByDefault;
+import org.apache.druid.query.aggregation.constant.LongConstantAggregator;
+import org.apache.druid.query.aggregation.constant.LongConstantBufferAggregator;
+import org.apache.druid.query.aggregation.constant.LongConstantVectorAggregator;
+import org.apache.druid.query.cache.CacheKeyBuilder;
+import org.apache.druid.segment.ColumnInspector;
+import org.apache.druid.segment.ColumnSelectorFactory;
+import org.apache.druid.segment.column.ValueType;
+import org.apache.druid.segment.vector.VectorColumnSelectorFactory;
+import org.apache.druid.utils.CollectionUtils;
+
+import javax.annotation.Nullable;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+
+@EverythingIsNonnullByDefault
+public class GroupingAggregatorFactory extends AggregatorFactory
+{
+  private static final Comparator<Long> VALUE_COMPARATOR = Long::compare;
+  private final String name;
+  private final List<String> groupings;
+  private final long value;
+  @Nullable
+  private final Set<String> keyDimensions;
+
+  @JsonCreator
+  public GroupingAggregatorFactory(
+      @JsonProperty("name") String name,
+      @JsonProperty("groupings") List<String> groupings
+  )
+  {
+    this(name, groupings, null);
+  }
+
+  @VisibleForTesting
+  GroupingAggregatorFactory(
+      String name,
+      List<String> groupings,
+      @Nullable Set<String> keyDimensions
+  )
+  {
+    Preconditions.checkNotNull(name, "Must have a valid, non-null aggregator name");
+    this.name = name;
+    this.groupings = groupings;
+    this.keyDimensions = keyDimensions;
+    value = groupingId(groupings, keyDimensions);
+  }
+
+  @Override
+  public Aggregator factorize(ColumnSelectorFactory metricFactory)
+  {
+    return new LongConstantAggregator(value);
+  }
+
+  @Override
+  public BufferAggregator factorizeBuffered(ColumnSelectorFactory metricFactory)
+  {
+    return new LongConstantBufferAggregator(value);
+  }
+
+  @Override
+  public VectorAggregator factorizeVector(VectorColumnSelectorFactory selectorFactory)
+  {
+    return new LongConstantVectorAggregator(value);
+  }
+
+  @Override
+  public boolean canVectorize(ColumnInspector columnInspector)
+  {
+    return true;
+  }
+
+  /**
+   * Replace the param {@code keyDimensions} with the new set of key dimensions
+   */
+  public GroupingAggregatorFactory withKeyDimensions(Set<String> newKeyDimensions)
+  {
+    return new GroupingAggregatorFactory(name, groupings, newKeyDimensions);
+  }
+
+  @Override
+  public Comparator getComparator()
+  {
+    return VALUE_COMPARATOR;
+  }
+
+  @JsonProperty
+  public List<String> getGroupings()
+  {
+    return groupings;
+  }
+
+  @Override
+  @JsonProperty
+  public String getName()
+  {
+    return name;
+  }
+
+  public long getValue()
+  {
+    return value;
+  }
+
+  @Nullable
+  @Override
+  public Object combine(@Nullable Object lhs, @Nullable Object rhs)
+  {
+    if (null == lhs) {
+      return rhs;
+    }
+    return lhs;
+  }
+
+  @Override
+  public AggregatorFactory getCombiningFactory()
+  {
+    return new GroupingAggregatorFactory(name, groupings, keyDimensions);
+  }
+
+  @Override
+  public List<AggregatorFactory> getRequiredColumns()
+  {
+    return Collections.singletonList(new GroupingAggregatorFactory(name, groupings, keyDimensions));
+  }
+
+  @Override
+  public Object deserialize(Object object)
+  {
+    return object;
+  }
+
+  @Nullable
+  @Override
+  public Object finalizeComputation(@Nullable Object object)
+  {
+    return object;
+  }
+
+  @Override
+  public List<String> requiredFields()
+  {
+    // The aggregator doesn't need to read any fields.
+    return Collections.emptyList();
+  }
+
+  @Override
+  public ValueType getType()
+  {
+    return ValueType.LONG;
+  }
+
+  @Override
+  public ValueType getFinalizedType()
+  {
+    return ValueType.LONG;
+  }
+
+  @Override
+  public int getMaxIntermediateSize()
+  {
+    return Long.BYTES;
+  }
+
+  @Override
+  public byte[] getCacheKey()
+  {
+    CacheKeyBuilder keyBuilder = new CacheKeyBuilder(AggregatorUtil.GROUPING_CACHE_TYPE_ID)
+        .appendStrings(groupings);
+    if (null != keyDimensions) {
+      keyBuilder.appendStrings(keyDimensions);
+    }
+    return keyBuilder.build();
+  }
+
+  /**
+   * Gives the list of grouping dimensions, return a long value where each bit at position X in the returned value
+   * corresponds to the dimension in groupings at same position X. X is the position relative to the right end. if
+   * keyDimensions contain the grouping dimension at position X, the bit is set to 1 at position X, otherwise it is
+   * set to 0. An example adapted from Microsoft SQL documentation

Review comment:
       I have seen that. Though it seems weird that 0 bit indicates that dimension is present, it seems it's not just postgres. I also checked that a commercial data warehouse follows the same logic as Postgres. will change this.

##########
File path: processing/src/main/java/org/apache/druid/query/aggregation/constant/LongConstantAggregator.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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 org.apache.druid.query.aggregation.constant;
+
+import org.apache.druid.query.aggregation.Aggregator;
+
+public class LongConstantAggregator implements Aggregator

Review comment:
       Ack

##########
File path: processing/src/main/java/org/apache/druid/query/aggregation/constant/LongConstantAggregator.java
##########
@@ -0,0 +1,62 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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 org.apache.druid.query.aggregation.constant;
+
+import org.apache.druid.query.aggregation.Aggregator;
+
+public class LongConstantAggregator implements Aggregator

Review comment:
       Those No-op aggregators are final classes so can't be extended. I don't see a clear reason why they are declared final. do you? 




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