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This module bridges Table/SQL API and runtime. It contains
all resources that are required during pre-flight and runtime
phase. The content of this module is work-in-progress. It will
replace flink-table-planner once it is stable. See FLINK-11439
and FLIP-32 for more details.
/*
* 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.flink.table.planner.functions.aggfunctions;
import org.apache.flink.table.api.DataTypes;
import org.apache.flink.table.api.TableException;
import org.apache.flink.table.expressions.Expression;
import org.apache.flink.table.expressions.UnresolvedReferenceExpression;
import org.apache.flink.table.types.DataType;
import static org.apache.flink.table.expressions.ApiExpressionUtils.unresolvedRef;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.concat;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.ifThenElse;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.isNull;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.literal;
import static org.apache.flink.table.planner.expressions.ExpressionBuilder.nullOf;
/** built-in listagg aggregate function. */
public class ListAggFunction extends DeclarativeAggregateFunction {
private int operandCount;
private UnresolvedReferenceExpression acc = unresolvedRef("concatAcc");
private UnresolvedReferenceExpression accDelimiter = unresolvedRef("accDelimiter");
private Expression delimiter;
private Expression operand;
public ListAggFunction(int operandCount) {
this.operandCount = operandCount;
if (operandCount == 1) {
delimiter = literal(",", DataTypes.STRING().notNull());
operand = operand(0);
} else {
delimiter = operand(1);
operand = operand(0);
}
}
@Override
public int operandCount() {
return operandCount;
}
@Override
public UnresolvedReferenceExpression[] aggBufferAttributes() {
return new UnresolvedReferenceExpression[] {accDelimiter, acc};
}
@Override
public DataType[] getAggBufferTypes() {
return new DataType[] {DataTypes.STRING(), DataTypes.STRING()};
}
@Override
public DataType getResultType() {
return DataTypes.STRING();
}
@Override
public Expression[] initialValuesExpressions() {
return new Expression[] {
/* delimiter */ literal(",", DataTypes.STRING().notNull()),
/* acc */ nullOf(DataTypes.STRING())
};
}
@Override
public Expression[] accumulateExpressions() {
return new Expression[] {
/* delimiter */
delimiter,
/* acc */
ifThenElse(
isNull(operand),
acc,
ifThenElse(isNull(acc), operand, concat(concat(acc, delimiter), operand)))
};
}
@Override
public Expression[] retractExpressions() {
throw new TableException("This function does not support retraction.");
}
@Override
public Expression[] mergeExpressions() {
return new Expression[] {
/* delimiter */
mergeOperand(accDelimiter),
/* acc */
ifThenElse(
isNull(mergeOperand(acc)),
acc,
ifThenElse(
isNull(acc),
mergeOperand(acc),
concat(concat(acc, mergeOperand(accDelimiter)), mergeOperand(acc))))
};
}
@Override
public Expression getValueExpression() {
return acc;
}
}