org.apache.druid.sql.calcite.aggregation.Aggregations Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* distributed with this work for additional information
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* 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
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package org.apache.druid.sql.calcite.aggregation;
import org.apache.calcite.rel.core.AggregateCall;
import org.apache.calcite.rel.core.Project;
import org.apache.calcite.rex.RexNode;
import org.apache.druid.segment.column.ValueType;
import org.apache.druid.sql.calcite.expression.DruidExpression;
import org.apache.druid.sql.calcite.expression.Expressions;
import org.apache.druid.sql.calcite.planner.PlannerContext;
import org.apache.druid.sql.calcite.table.RowSignature;
import javax.annotation.Nullable;
import java.util.List;
import java.util.Objects;
import java.util.function.Function;
import java.util.stream.Collectors;
public class Aggregations
{
private Aggregations()
{
// No instantiation.
}
/**
* Get Druid expressions that correspond to "simple" aggregator inputs. This is used by standard sum/min/max
* aggregators, which have the following properties:
*
* 1) They can take direct field accesses or expressions as inputs.
* 2) They cannot implicitly cast strings to numbers when using a direct field access.
*
* @param plannerContext SQL planner context
* @param rowSignature input row signature
* @param call aggregate call object
* @param project project that should be applied before aggregation; may be null
*
* @return list of expressions corresponding to aggregator arguments, or null if any cannot be translated
*/
@Nullable
public static List getArgumentsForSimpleAggregator(
final PlannerContext plannerContext,
final RowSignature rowSignature,
final AggregateCall call,
@Nullable final Project project
)
{
final List args = call
.getArgList()
.stream()
.map(i -> Expressions.fromFieldAccess(rowSignature, project, i))
.map(rexNode -> toDruidExpressionForSimpleAggregator(plannerContext, rowSignature, rexNode))
.collect(Collectors.toList());
if (args.stream().noneMatch(Objects::isNull)) {
return args;
} else {
return null;
}
}
private static DruidExpression toDruidExpressionForSimpleAggregator(
final PlannerContext plannerContext,
final RowSignature rowSignature,
final RexNode rexNode
)
{
final DruidExpression druidExpression = Expressions.toDruidExpression(plannerContext, rowSignature, rexNode);
if (druidExpression == null) {
return null;
}
if (druidExpression.isSimpleExtraction() &&
(!druidExpression.isDirectColumnAccess()
|| rowSignature.getColumnType(druidExpression.getDirectColumn()) == ValueType.STRING)) {
// Aggregators are unable to implicitly cast strings to numbers.
// So remove the simple extraction, which forces the expression to be used instead of the direct column access.
return druidExpression.map(simpleExtraction -> null, Function.identity());
} else {
return druidExpression;
}
}
}