[GitHub] [druid] jihoonson commented on a change in pull request #11157: ARRAY_AGG sql aggregator function

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

jihoonson commented on a change in pull request #11157:
URL: https://github.com/apache/druid/pull/11157#discussion_r622725800



##########
File path: sql/src/main/java/org/apache/druid/sql/calcite/aggregation/builtin/ArraySqlAggregator.java
##########
@@ -0,0 +1,221 @@
+/*
+ * 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.sql.calcite.aggregation.builtin;
+
+import com.google.common.collect.ImmutableSet;
+import org.apache.calcite.rel.core.AggregateCall;
+import org.apache.calcite.rel.core.Project;
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.rex.RexLiteral;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.sql.SqlAggFunction;
+import org.apache.calcite.sql.SqlFunctionCategory;
+import org.apache.calcite.sql.SqlKind;
+import org.apache.calcite.sql.SqlOperatorBinding;
+import org.apache.calcite.sql.type.InferTypes;
+import org.apache.calcite.sql.type.OperandTypes;
+import org.apache.calcite.sql.type.SqlReturnTypeInference;
+import org.apache.calcite.sql.type.SqlTypeFamily;
+import org.apache.calcite.sql.type.SqlTypeUtil;
+import org.apache.calcite.util.Optionality;
+import org.apache.druid.java.util.common.HumanReadableBytes;
+import org.apache.druid.java.util.common.ISE;
+import org.apache.druid.java.util.common.StringUtils;
+import org.apache.druid.math.expr.ExprMacroTable;
+import org.apache.druid.query.aggregation.ExpressionLambdaAggregatorFactory;
+import org.apache.druid.segment.VirtualColumn;
+import org.apache.druid.segment.column.RowSignature;
+import org.apache.druid.segment.column.ValueType;
+import org.apache.druid.sql.calcite.aggregation.Aggregation;
+import org.apache.druid.sql.calcite.aggregation.SqlAggregator;
+import org.apache.druid.sql.calcite.expression.DruidExpression;
+import org.apache.druid.sql.calcite.expression.Expressions;
+import org.apache.druid.sql.calcite.planner.Calcites;
+import org.apache.druid.sql.calcite.planner.PlannerContext;
+import org.apache.druid.sql.calcite.rel.VirtualColumnRegistry;
+
+import javax.annotation.Nullable;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+public class ArraySqlAggregator implements SqlAggregator
+{
+  private static final String NAME = "ARRAY_AGG";
+
+  @Override
+  public SqlAggFunction calciteFunction()
+  {
+    return new ArrayAggFunction();

Review comment:
       nit: is it worth making it as a singleton?

##########
File path: docs/querying/sql.md
##########
@@ -353,6 +353,10 @@ Only the COUNT aggregation can accept DISTINCT.
 |`ANY_VALUE(expr)`|Returns any value of `expr` including null. `expr` must be numeric. This aggregator can simplify and optimize the performance by returning the first encountered value (including null)|
 |`ANY_VALUE(expr, maxBytesPerString)`|Like `ANY_VALUE(expr)`, but for strings. The `maxBytesPerString` parameter determines how much aggregation space to allocate per string. Strings longer than this limit will be truncated. This parameter should be set as low as possible, since high values will lead to wasted memory.|
 |`GROUPING(expr, expr...)`|Returns a number to indicate which groupBy dimension is included in a row, when using `GROUPING SETS`. Refer to [additional documentation](aggregations.md#grouping-aggregator) on how to infer this number.|
+|`ARRAY_AGG(expr)`|Collects all values of `expr` into an ARRAY, including null values, with the default limit on aggregation size of 1024 bytes. `ORDER BY` on the `ARRAY_AGG` expression is not currently supported.|
+|`ARRAY_AGG(DISTINCT expr)`|Collects all distinct values of `expr` into an ARRAY, including null values, with the default limit on aggregation size of 1024 bytes per aggregate. `ORDER BY` on the `ARRAY_AGG` expression is not currently supported.|
+|`ARRAY_AGG(expr, maxSizeBytes)`|Collects all values of `expr` into an ARRAY, including null values, with specified maximum byte size per aggregate. `ORDER BY` on the `ARRAY_AGG` expression is not currently supported.|
+|`ARRAY_AGG(DISTINCT expr, maxSizeBytes)`|Collects all distinct values of `expr` into an ARRAY, including null values, with specified maximum byte size per aggregate. `ORDER BY` on the `ARRAY_AGG` expression is not currently supported.|

Review comment:
       Maybe better to consolidate these into 2, such as `ARRAY_AGG(expr)` and `ARRAY_AGG(DISTINCT expr)` with an optional size parameter as in https://github.com/apache/druid/pull/11157/files#diff-cada0a48f60f548ce82ef1008918e0aed6b3de0339312c662761855a35dde6c6L339.

##########
File path: sql/src/main/java/org/apache/druid/sql/calcite/aggregation/builtin/ArraySqlAggregator.java
##########
@@ -0,0 +1,221 @@
+/*
+ * 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.sql.calcite.aggregation.builtin;
+
+import com.google.common.collect.ImmutableSet;
+import org.apache.calcite.rel.core.AggregateCall;
+import org.apache.calcite.rel.core.Project;
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.rex.RexLiteral;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.sql.SqlAggFunction;
+import org.apache.calcite.sql.SqlFunctionCategory;
+import org.apache.calcite.sql.SqlKind;
+import org.apache.calcite.sql.SqlOperatorBinding;
+import org.apache.calcite.sql.type.InferTypes;
+import org.apache.calcite.sql.type.OperandTypes;
+import org.apache.calcite.sql.type.SqlReturnTypeInference;
+import org.apache.calcite.sql.type.SqlTypeFamily;
+import org.apache.calcite.sql.type.SqlTypeUtil;
+import org.apache.calcite.util.Optionality;
+import org.apache.druid.java.util.common.HumanReadableBytes;
+import org.apache.druid.java.util.common.ISE;
+import org.apache.druid.java.util.common.StringUtils;
+import org.apache.druid.math.expr.ExprMacroTable;
+import org.apache.druid.query.aggregation.ExpressionLambdaAggregatorFactory;
+import org.apache.druid.segment.VirtualColumn;
+import org.apache.druid.segment.column.RowSignature;
+import org.apache.druid.segment.column.ValueType;
+import org.apache.druid.sql.calcite.aggregation.Aggregation;
+import org.apache.druid.sql.calcite.aggregation.SqlAggregator;
+import org.apache.druid.sql.calcite.expression.DruidExpression;
+import org.apache.druid.sql.calcite.expression.Expressions;
+import org.apache.druid.sql.calcite.planner.Calcites;
+import org.apache.druid.sql.calcite.planner.PlannerContext;
+import org.apache.druid.sql.calcite.rel.VirtualColumnRegistry;
+
+import javax.annotation.Nullable;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+public class ArraySqlAggregator implements SqlAggregator
+{
+  private static final String NAME = "ARRAY_AGG";
+
+  @Override
+  public SqlAggFunction calciteFunction()
+  {
+    return new ArrayAggFunction();
+  }
+
+  @Nullable
+  @Override
+  public Aggregation toDruidAggregation(
+      PlannerContext plannerContext,
+      RowSignature rowSignature,
+      VirtualColumnRegistry virtualColumnRegistry,
+      RexBuilder rexBuilder,
+      String name,
+      AggregateCall aggregateCall,
+      Project project,
+      List<Aggregation> existingAggregations,
+      boolean finalizeAggregations
+  )
+  {
+
+    final List<DruidExpression> arguments = aggregateCall
+        .getArgList()
+        .stream()
+        .map(i -> Expressions.fromFieldAccess(rowSignature, project, i))
+        .map(rexNode -> Expressions.toDruidExpression(plannerContext, rowSignature, rexNode))
+        .collect(Collectors.toList());
+
+    if (arguments.stream().anyMatch(Objects::isNull)) {
+      return null;
+    }
+
+    Integer maxSizeBytes = null;
+    if (arguments.size() > 1) {
+      RexNode maxBytes = Expressions.fromFieldAccess(
+          rowSignature,
+          project,
+          aggregateCall.getArgList().get(1)
+      );
+      if (!maxBytes.isA(SqlKind.LITERAL)) {
+        // maxBytes must be a literal
+        return null;
+      }
+      maxSizeBytes = ((Number) RexLiteral.value(maxBytes)).intValue();
+    }
+    final DruidExpression arg = arguments.get(0);
+    final ExprMacroTable macroTable = plannerContext.getExprMacroTable();
+
+    final String fieldName;
+    final String initialvalue;
+    final ValueType elementType;
+    final ValueType druidType = Calcites.getValueTypeForRelDataTypeFull(aggregateCall.getType());
+    switch (druidType) {

Review comment:
       This can throw NPE since `druidType` can be null.

##########
File path: sql/src/main/java/org/apache/druid/sql/calcite/aggregation/builtin/ArraySqlAggregator.java
##########
@@ -0,0 +1,221 @@
+/*
+ * 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.sql.calcite.aggregation.builtin;
+
+import com.google.common.collect.ImmutableSet;
+import org.apache.calcite.rel.core.AggregateCall;
+import org.apache.calcite.rel.core.Project;
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.rex.RexLiteral;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.sql.SqlAggFunction;
+import org.apache.calcite.sql.SqlFunctionCategory;
+import org.apache.calcite.sql.SqlKind;
+import org.apache.calcite.sql.SqlOperatorBinding;
+import org.apache.calcite.sql.type.InferTypes;
+import org.apache.calcite.sql.type.OperandTypes;
+import org.apache.calcite.sql.type.SqlReturnTypeInference;
+import org.apache.calcite.sql.type.SqlTypeFamily;
+import org.apache.calcite.sql.type.SqlTypeUtil;
+import org.apache.calcite.util.Optionality;
+import org.apache.druid.java.util.common.HumanReadableBytes;
+import org.apache.druid.java.util.common.ISE;
+import org.apache.druid.java.util.common.StringUtils;
+import org.apache.druid.math.expr.ExprMacroTable;
+import org.apache.druid.query.aggregation.ExpressionLambdaAggregatorFactory;
+import org.apache.druid.segment.VirtualColumn;
+import org.apache.druid.segment.column.RowSignature;
+import org.apache.druid.segment.column.ValueType;
+import org.apache.druid.sql.calcite.aggregation.Aggregation;
+import org.apache.druid.sql.calcite.aggregation.SqlAggregator;
+import org.apache.druid.sql.calcite.expression.DruidExpression;
+import org.apache.druid.sql.calcite.expression.Expressions;
+import org.apache.druid.sql.calcite.planner.Calcites;
+import org.apache.druid.sql.calcite.planner.PlannerContext;
+import org.apache.druid.sql.calcite.rel.VirtualColumnRegistry;
+
+import javax.annotation.Nullable;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+public class ArraySqlAggregator implements SqlAggregator
+{
+  private static final String NAME = "ARRAY_AGG";
+
+  @Override
+  public SqlAggFunction calciteFunction()
+  {
+    return new ArrayAggFunction();
+  }
+
+  @Nullable
+  @Override
+  public Aggregation toDruidAggregation(
+      PlannerContext plannerContext,
+      RowSignature rowSignature,
+      VirtualColumnRegistry virtualColumnRegistry,
+      RexBuilder rexBuilder,
+      String name,
+      AggregateCall aggregateCall,
+      Project project,
+      List<Aggregation> existingAggregations,
+      boolean finalizeAggregations
+  )
+  {
+
+    final List<DruidExpression> arguments = aggregateCall
+        .getArgList()
+        .stream()
+        .map(i -> Expressions.fromFieldAccess(rowSignature, project, i))
+        .map(rexNode -> Expressions.toDruidExpression(plannerContext, rowSignature, rexNode))
+        .collect(Collectors.toList());
+
+    if (arguments.stream().anyMatch(Objects::isNull)) {
+      return null;
+    }
+
+    Integer maxSizeBytes = null;

Review comment:
       nit: I think probably most people just use the byte size for this function, but it seems that it can be a string literal which will allow using the `HumanReadable` format?




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