org.apache.flink.table.planner.codegen.GeneratedExpression.scala Maven / Gradle / Ivy

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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.

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/*
 * 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.codegen

import org.apache.flink.table.planner.codegen.CodeGenUtils.boxedTypeTermForType
import org.apache.flink.table.runtime.typeutils.TypeCheckUtils
import org.apache.flink.table.types.logical.LogicalType

/**
  * Describes a generated expression.
  *
  * @param resultTerm term to access the result of the expression
  * @param nullTerm boolean term that indicates if expression is null
  * @param code code necessary to produce resultTerm and nullTerm
  * @param resultType type of the resultTerm
  * @param literalValue None if the expression is not literal. Otherwise it represent the
  *                     original object of the literal.
  */
case class GeneratedExpression(
  resultTerm: String,
  nullTerm: String,
  code: String,
  resultType: LogicalType,
  literalValue: Option[Any] = None) {

  /**
    * Indicates a constant expression do not reference input and can thus be used
    * in the member area (e.g. as constructor parameter of a reusable instance)
    *
    * @return true if the expression is literal
    */
  def literal: Boolean = literalValue.isDefined

  /**
    * Copy result term to target term if the reference is changed.
    * Note: We must ensure that the target can only be copied out, so that its object is definitely
    * a brand new reference, not the object being re-used.
    * @param target the target term that cannot be assigned a reusable reference.
    * @return code.
    */
  def copyResultTermToTargetIfChanged(ctx: CodeGeneratorContext, target: String): String = {
    if (TypeCheckUtils.isMutable(resultType)) {
      val typeTerm = boxedTypeTermForType(resultType)
      val serTerm = ctx.addReusableTypeSerializer(resultType)
      s"""
         |if ($target != $resultTerm) {
         |  $target = (($typeTerm) $serTerm.copy($resultTerm));
         |}
       """.stripMargin
    } else {
      s"$target = $resultTerm;"
    }
  }

  /**
    * Deep copy the generated expression.
    *
    * NOTE: Please use this method when the result will be buffered.
    * This method makes sure a new object/data is created when the type is mutable.
    */
  def deepCopy(ctx: CodeGeneratorContext): GeneratedExpression = {
    // only copy when type is mutable
    if (TypeCheckUtils.isMutable(resultType)) {
      // if the type need copy, it must be a boxed type
      val typeTerm = boxedTypeTermForType(resultType)
      val serTerm = ctx.addReusableTypeSerializer(resultType)
      val newResultTerm = ctx.addReusableLocalVariable(typeTerm, "field")
      val newCode =
        s"""
           |$code
           |$newResultTerm = $resultTerm;
           |if (!$nullTerm) {
           |  $newResultTerm = ($typeTerm) ($serTerm.copy($newResultTerm));
           |}
        """.stripMargin
      GeneratedExpression(newResultTerm, nullTerm, newCode, resultType, literalValue)
    } else {
      this
    }
  }
}

object GeneratedExpression {
  val ALWAYS_NULL = "true"
  val NEVER_NULL = "false"
  val NO_CODE = ""
}