core/src/main/java/org/apache/calcite/rel/rules/ProjectJoinTransposeRule.java

/*
 * 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.calcite.rel.rules;

import org.apache.calcite.plan.RelOptRuleCall;
import org.apache.calcite.plan.RelOptUtil;
import org.apache.calcite.plan.RelRule;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.Join;
import org.apache.calcite.rel.core.Project;
import org.apache.calcite.rel.logical.LogicalJoin;
import org.apache.calcite.rel.logical.LogicalProject;
import org.apache.calcite.rel.type.RelDataTypeField;
import org.apache.calcite.rex.RexCall;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.rex.RexOver;
import org.apache.calcite.rex.RexShuttle;
import org.apache.calcite.tools.RelBuilderFactory;

import org.immutables.value.Value;

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

import static java.util.Objects.requireNonNull;

/**
 * Planner rule that pushes a {@link org.apache.calcite.rel.core.Project}
 * past a {@link org.apache.calcite.rel.core.Join}
 * by splitting the projection into a projection on top of each child of
 * the join.
 *
 * @see CoreRules#PROJECT_JOIN_TRANSPOSE
 */
@Value.Enclosing
public class ProjectJoinTransposeRule
    extends RelRule<ProjectJoinTransposeRule.Config>
    implements TransformationRule {

  /** Creates a ProjectJoinTransposeRule. */
  protected ProjectJoinTransposeRule(Config config) {
    super(config);
  }

  @Deprecated // to be removed before 2.0
  public ProjectJoinTransposeRule(
      Class<? extends Project> projectClass,
      Class<? extends Join> joinClass,
      PushProjector.ExprCondition preserveExprCondition,
      RelBuilderFactory relBuilderFactory) {
    this(Config.DEFAULT
        .withRelBuilderFactory(relBuilderFactory)
        .as(Config.class)
        .withOperandFor(projectClass, joinClass)
        .withPreserveExprCondition(preserveExprCondition));
  }

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

  @Override public void onMatch(RelOptRuleCall call) {
    final Project origProject = call.rel(0);
    final Join join = call.rel(1);

    // Normalize the join condition so we don't end up misidentified expanded
    // form of IS NOT DISTINCT FROM as PushProject also visit the filter condition
    // and push down expressions.
    RexNode joinFilter = join.getCondition().accept(new RexShuttle() {
      @Override public RexNode visitCall(RexCall rexCall) {
        final RexNode node = super.visitCall(rexCall);
        if (!(node instanceof RexCall)) {
          return node;
        }
        return RelOptUtil.collapseExpandedIsNotDistinctFromExpr((RexCall) node,
            call.builder().getRexBuilder());
      }
    });

    // locate all fields referenced in the projection and join condition;
    // determine which inputs are referenced in the projection and
    // join condition; if all fields are being referenced and there are no
    // special expressions, no point in proceeding any further
    final PushProjector pushProjector =
        new PushProjector(
            origProject,
            joinFilter,
            join,
            config.preserveExprCondition(),
            call.builder());
    if (pushProjector.locateAllRefs()) {
      return;
    }

    // create left and right projections, projecting only those
    // fields referenced on each side
    final RelNode leftProject =
        pushProjector.createProjectRefsAndExprs(
            join.getLeft(),
            true,
            false);
    final RelNode rightProject =
        pushProjector.createProjectRefsAndExprs(
            join.getRight(),
            true,
            true);

    // convert the join condition to reference the projected columns
    RexNode newJoinFilter = null;
    int[] adjustments = pushProjector.getAdjustments();
    if (joinFilter != null) {
      List<RelDataTypeField> projectJoinFieldList = new ArrayList<>();
      projectJoinFieldList.addAll(
          join.getSystemFieldList());
      projectJoinFieldList.addAll(
          leftProject.getRowType().getFieldList());
      projectJoinFieldList.addAll(
          rightProject.getRowType().getFieldList());
      newJoinFilter =
          pushProjector.convertRefsAndExprs(
              joinFilter,
              projectJoinFieldList,
              adjustments);
    }

    // create a new join with the projected children
    final Join newJoin =
        join.copy(
            join.getTraitSet(),
            requireNonNull(newJoinFilter, "newJoinFilter must not be null"),
            leftProject,
            rightProject,
            join.getJoinType(),
            join.isSemiJoinDone());

    // put the original project on top of the join, converting it to
    // reference the modified projection list
    final RelNode topProject =
        pushProjector.createNewProject(newJoin, adjustments);

    call.transformTo(topProject);
  }

  /** Rule configuration. */
  @Value.Immutable(singleton = false)
  public interface Config extends RelRule.Config {
    Config DEFAULT = ImmutableProjectJoinTransposeRule.Config.builder()
        .withPreserveExprCondition(expr -> !(expr instanceof RexOver))
        .build()
        .withOperandFor(LogicalProject.class, LogicalJoin.class);

    @Override default ProjectJoinTransposeRule toRule() {
      return new ProjectJoinTransposeRule(this);
    }

    /** Defines when an expression should not be pushed. */
    PushProjector.ExprCondition preserveExprCondition();

    /** Sets {@link #preserveExprCondition()}. */
    Config withPreserveExprCondition(PushProjector.ExprCondition condition);

    /** Defines an operand tree for the given classes. */
    default Config withOperandFor(Class<? extends Project> projectClass,
        Class<? extends Join> joinClass) {
      return withOperandSupplier(b0 ->
          b0.operand(projectClass).oneInput(b1 ->
              b1.operand(joinClass).anyInputs()))
          .as(Config.class);
    }
  }
}