Github user shaoxuan-wang commented on a diff in the pull request: https://github.com/apache/flink/pull/3809#discussion_r114692346 --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/utils/AggSqlFunction.scala --- @@ -0,0 +1,177 @@ +/* + * 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.functions.utils + +import org.apache.calcite.rel.`type`.RelDataType +import org.apache.calcite.sql._ +import org.apache.calcite.sql.`type`._ +import org.apache.calcite.sql.`type`.SqlOperandTypeChecker.Consistency +import org.apache.calcite.sql.parser.SqlParserPos +import org.apache.calcite.sql.validate.SqlUserDefinedAggFunction +import org.apache.flink.api.common.typeinfo._ +import org.apache.flink.table.api.ValidationException +import org.apache.flink.table.calcite.FlinkTypeFactory +import org.apache.flink.table.functions.AggregateFunction +import org.apache.flink.table.functions.utils.AggSqlFunction.{createOperandTypeChecker, createOperandTypeInference, createReturnTypeInference} +import org.apache.flink.table.functions.utils.UserDefinedFunctionUtils._ + +/** + * Calcite wrapper for user-defined aggregate functions. + * + * @param name function name (used by SQL parser) + * @param aggregateFunction aggregate function to be called + * @param returnType the type information of returned value + * @param typeFactory type factory for converting Flink's between Calcite's types + */ +class AggSqlFunction( + name: String, + aggregateFunction: AggregateFunction[_, _], + returnType: TypeInformation[_], + typeFactory: FlinkTypeFactory) + extends SqlUserDefinedAggFunction( + new SqlIdentifier(name, SqlParserPos.ZERO), + createReturnTypeInference(returnType, typeFactory), + createOperandTypeInference(aggregateFunction, typeFactory), + createOperandTypeChecker(aggregateFunction), + // Do not need to provide a calcite aggregateFunction here. Flink aggregateion function + // will be generated when translating the calcite relnode to flink runtime execution plan + null + ) { + + def getFunction: AggregateFunction[_, _] = aggregateFunction +} + +object AggSqlFunction { + + def apply( + name: String, + aggregateFunction: AggregateFunction[_, _], + returnType: TypeInformation[_], + typeFactory: FlinkTypeFactory): AggSqlFunction = { + + new AggSqlFunction(name, aggregateFunction, returnType, typeFactory) + } + + private[flink] def createOperandTypeInference( + aggregateFunction: AggregateFunction[_, _], + typeFactory: FlinkTypeFactory) + : SqlOperandTypeInference = { + /** + * Operand type inference based on [[AggregateFunction]] given information. + */ + new SqlOperandTypeInference { + override def inferOperandTypes( + callBinding: SqlCallBinding, + returnType: RelDataType, + operandTypes: Array[RelDataType]): Unit = { + + val operandTypeInfo = getOperandTypeInfo(callBinding) + + val foundSignature = getAccumulateMethodSignature(aggregateFunction, operandTypeInfo) + .getOrElse(throw new ValidationException(s"Operand types of could not be inferred.")) + + val inferredTypes = getParameterTypes(aggregateFunction, foundSignature.drop(1)) + .map(typeFactory.createTypeFromTypeInfo) + + for (i <- operandTypes.indices) { + if (i < inferredTypes.length - 1) { + operandTypes(i) = inferredTypes(i) + } else if (null != inferredTypes.last.getComponentType) { --- End diff -- Yes, if the last parameter is a component, say Array[Int]. We want to get the type of Int, not the type of Array.
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