org.apache.flink.table.planner.plan.rules.logical.SimplifyJoinConditionRule.scala Maven / Gradle / Ivy

/*
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 * 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
 *
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package org.apache.flink.table.planner.plan.rules.logical

import org.apache.flink.table.planner.plan.utils.FlinkRexUtil

import org.apache.calcite.plan.RelOptRule.{any, operand}
import org.apache.calcite.plan.{RelOptRule, RelOptRuleCall}
import org.apache.calcite.rel.logical.LogicalJoin
import org.apache.calcite.rex._

/**
  * Planner rule that apply various simplifying transformations on join condition.
  * e.g.
  * reduce same expressions: a=b AND b=a -> a=b,
  * simplify boolean expressions: x = 1 AND FALSE -> FALSE,
  * simplify cast expressions: CAST('123' as integer) -> 123
  */
class SimplifyJoinConditionRule
  extends RelOptRule(
    operand(classOf[LogicalJoin], any()),
    "SimplifyJoinConditionRule") {

  override def onMatch(call: RelOptRuleCall): Unit = {
    val join: LogicalJoin = call.rel(0)
    val condition = join.getCondition

    if (join.getCondition.isAlwaysTrue) {
      return
    }

    val simpleCondExp = FlinkRexUtil.simplify(join.getCluster.getRexBuilder, condition)
    val newCondExp = RexUtil.pullFactors(join.getCluster.getRexBuilder, simpleCondExp)

    if (newCondExp.equals(condition)) {
      return
    }

    val newJoin = join.copy(
      join.getTraitSet,
      newCondExp,
      join.getLeft,
      join.getRight,
      join.getJoinType,
      join.isSemiJoinDone)

    call.transformTo(newJoin)
    call.getPlanner.prune(join)
  }
}

object SimplifyJoinConditionRule {
  val INSTANCE = new SimplifyJoinConditionRule
}