com.hazelcast.org.apache.calcite.rel.rules.ProjectSetOpTransposeRule Maven / Gradle / Ivy

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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 com.hazelcast.org.apache.calcite.rel.rules;

import com.hazelcast.org.apache.calcite.plan.RelOptRule;
import com.hazelcast.org.apache.calcite.plan.RelOptRuleCall;
import com.hazelcast.org.apache.calcite.rel.RelNode;
import com.hazelcast.org.apache.calcite.rel.core.Project;
import com.hazelcast.org.apache.calcite.rel.core.RelFactories;
import com.hazelcast.org.apache.calcite.rel.core.SetOp;
import com.hazelcast.org.apache.calcite.rel.logical.LogicalProject;
import com.hazelcast.org.apache.calcite.rex.RexInputRef;
import com.hazelcast.org.apache.calcite.rex.RexOver;
import com.hazelcast.org.apache.calcite.tools.RelBuilderFactory;

import java.util.ArrayList;
import java.util.List;

/**
 * Planner rule that pushes
 * a {@link com.hazelcast.org.apache.calcite.rel.logical.LogicalProject}
 * past a {@link com.hazelcast.org.apache.calcite.rel.core.SetOp}.
 *
 * The children of the {@code SetOp} will project
 * only the {@link RexInputRef}s referenced in the original
 * {@code LogicalProject}.
 */
public class ProjectSetOpTransposeRule extends RelOptRule implements TransformationRule {
  public static final ProjectSetOpTransposeRule INSTANCE =
      new ProjectSetOpTransposeRule(expr -> !(expr instanceof RexOver),
          RelFactories.LOGICAL_BUILDER);

  //~ Instance fields --------------------------------------------------------

  /**
   * Expressions that should be preserved in the projection
   */
  private PushProjector.ExprCondition preserveExprCondition;

  //~ Constructors -----------------------------------------------------------

  /**
   * Creates a ProjectSetOpTransposeRule with an explicit condition whether
   * to preserve expressions.
   *
   * @param preserveExprCondition Condition whether to preserve expressions
   */
  public ProjectSetOpTransposeRule(
      PushProjector.ExprCondition preserveExprCondition,
      RelBuilderFactory relBuilderFactory) {
    super(
        operand(
            LogicalProject.class,
            operand(SetOp.class, any())),
        relBuilderFactory, null);
    this.preserveExprCondition = preserveExprCondition;
  }

  //~ Methods ----------------------------------------------------------------

  // implement RelOptRule
  public void onMatch(RelOptRuleCall call) {
    LogicalProject origProj = call.rel(0);
    SetOp setOp = call.rel(1);

    // cannot push project past a distinct
    if (!setOp.all) {
      return;
    }

    // locate all fields referenced in the projection
    PushProjector pushProject =
        new PushProjector(
            origProj, null, setOp, preserveExprCondition, call.builder());
    pushProject.locateAllRefs();

    List newSetOpInputs = new ArrayList<>();
    int[] adjustments = pushProject.getAdjustments();

    final RelNode node;
    if (RexOver.containsOver(origProj.getProjects(), null)) {
      // should not push over past setop but can push its operand down.
      for (RelNode input : setOp.getInputs()) {
        Project p = pushProject.createProjectRefsAndExprs(input, true, false);
        // make sure that it is not a trivial project to avoid infinite loop.
        if (p.getRowType().equals(input.getRowType())) {
          return;
        }
        newSetOpInputs.add(p);
      }
      SetOp newSetOp =
          setOp.copy(setOp.getTraitSet(), newSetOpInputs);
      node = pushProject.createNewProject(newSetOp, adjustments);
    } else {
      // push some expressions below the setop; this
      // is different from pushing below a join, where we decompose
      // to try to keep expensive expressions above the join,
      // because UNION ALL does not have any filtering effect,
      // and it is the only operator this rule currently acts on
      setOp.getInputs().forEach(input ->
          newSetOpInputs.add(
              pushProject.createNewProject(
                  pushProject.createProjectRefsAndExprs(
                      input, true, false), adjustments)));
      node = setOp.copy(setOp.getTraitSet(), newSetOpInputs);
    }

    call.transformTo(node);
  }
}