jihoonson commented on a change in pull request #11157:
URL: https://github.com/apache/druid/pull/11157#discussion_r625507597
##########
File path: docs/querying/sql.md
##########
@@ -353,6 +353,8 @@ 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, [size])`|Collects all values of `expr` into an ARRAY,
including null values, with `size` in bytes limit on aggregation size (default
of 1024 bytes). Use of `ORDER BY` within the `ARRAY_AGG` expression is not
currently supported, and the ordering of results within the output array may
vary depending on processing order.|
Review comment:
Can you please document that this function can return null when it
processes no rows?
##########
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:
👍
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