content: /*
   * 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.RelRule;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Intersect;
  import org.apache.calcite.rel.core.JoinRelType;
  import org.apache.calcite.rel.logical.LogicalIntersect;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rex.RexBuilder;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.rex.RexUtil;
  import org.apache.calcite.tools.RelBuilder;
  
  import org.immutables.value.Value;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * Planner rule that translates a {@link Intersect}
   * to a series of {@link org.apache.calcite.rel.core.Join} that type is
   * {@link JoinRelType#SEMI}. This rule supports n-way Intersect conversion,
   * as this rule can be repeatedly applied during query optimization to
   * refine the plan.
   *
   * <h2>Example</h2>
   *
   <p>Original sql:
   * <pre>{@code
   * select ename from emp where deptno = 10
   * intersect
   * select deptno from emp where ename in ('a', 'b')
   * intersect
   * select ename from empnullables
   * }</pre>
   *
   * <p>Original plan:
   * <pre>{@code
   * LogicalIntersect(all=[false])
   *   LogicalProject(ENAME=[$1])
   *     LogicalFilter(condition=[=($7, 10)])
   *       LogicalTableScan(table=[[CATALOG, SALES, EMP]])
   *   LogicalProject(DEPTNO=[CAST($7):VARCHAR NOT NULL])
   *     LogicalFilter(condition=[OR(=($1, 'a'), =($1, 'b'))])
   *       LogicalTableScan(table=[[CATALOG, SALES, EMP]])
   *   LogicalProject(ENAME=[$1])
   *     LogicalTableScan(table=[[CATALOG, SALES, EMPNULLABLES]])
   * }</pre>
   *
   * <p>Plan after conversion:
   * <pre>{@code
   * LogicalAggregate(group=[{0}])
   *   LogicalJoin(condition=[IS NOT DISTINCT FROM($0, $1)], joinType=[semi])
   *     LogicalJoin(condition=[IS NOT DISTINCT FROM($0, $1)], joinType=[semi])
   *       LogicalProject(ENAME=[CAST($0):VARCHAR])
   *         LogicalProject(ENAME=[$1])
   *           LogicalFilter(condition=[=($7, 10)])
   *             LogicalTableScan(table=[[CATALOG, SALES, EMP]])
   *       LogicalProject(ENAME=[CAST($0):VARCHAR])
   *         LogicalProject(DEPTNO=[CAST($7):VARCHAR NOT NULL])
   *           LogicalFilter(condition=[OR(=($1, 'a'), =($1, 'b'))])
   *             LogicalTableScan(table=[[CATALOG, SALES, EMP]])
   *     LogicalProject(ENAME=[CAST($0):VARCHAR])
   *       LogicalProject(ENAME=[$1])
   *         LogicalTableScan(table=[[CATALOG, SALES, EMPNULLABLES]])
   * }</pre>
  */
  @Value.Enclosing
  public class IntersectToSemiJoinRule
      extends RelRule<IntersectToSemiJoinRule.Config>
      implements TransformationRule {
  
    /** Creates an IntersectToSemiJoinRule. */
    protected IntersectToSemiJoinRule(Config config) {
      super(config);
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public void onMatch(RelOptRuleCall call) {
      final Intersect intersect = call.rel(0);
      if (intersect.all) {
        return; // nothing we can do
      }
  
      final RelBuilder builder = call.builder();
      final RexBuilder rexBuilder = builder.getRexBuilder();
  
      List<RelNode> inputs = intersect.getInputs();
      if (inputs.size() < 2) {
        return;
      }
  
      final RelDataType leastRowType = intersect.getRowType();
      RelNode current = inputs.get(0);
  
      for (int i = 1; i < inputs.size(); i++) {
        RelNode next = inputs.get(i);
  
        // cast columns of the join inputs to the least types (global)
        final RelNode leftCasted = projectJoinInput(builder, leastRowType, current);
        final RelNode rightCasted = projectJoinInput(builder, leastRowType, next);
        builder.push(leftCasted).push(rightCasted);
  
        // compute the join condition over plain fields from the projections of left/right inputs
        final int fieldCount = leastRowType.getFieldCount();
        final List<RexNode> joinPredicates = new ArrayList<>(fieldCount);
        for (int j = 0; j < fieldCount; j++) {
          joinPredicates.add(
              builder.isNotDistinctFrom(
              builder.field(2, 0, j),
              builder.field(2, 1, j)));
        }
  
        final RexNode condition = RexUtil.composeConjunction(rexBuilder, joinPredicates);
        builder.join(JoinRelType.SEMI, condition);
        current = builder.peek();
      }
  
      builder.distinct().convert(leastRowType, true);
      call.transformTo(builder.build());
    }
  
    private RelNode projectJoinInput(
        RelBuilder builder, RelDataType leastRowType, RelNode joinInput) {
      builder.push(joinInput);
  
      final int fieldCount = joinInput.getRowType().getFieldCount();
      final List<String> names = leastRowType.getFieldNames();
      final List<RexNode> joinKeys = new ArrayList<>(fieldCount);
      final RexBuilder rexBuilder = builder.getRexBuilder();
      for (int j = 0; j < fieldCount; j++) {
        final RelDataType leastType = leastRowType.getFieldList().get(j).getType();
        joinKeys.add(rexBuilder.makeCast(leastType, builder.field(j)));
      }
  
      return builder.project(joinKeys, names).build();
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableIntersectToSemiJoinRule.Config.of()
          .withOperandFor(LogicalIntersect.class);
  
      @Override default IntersectToSemiJoinRule toRule() {
        return new IntersectToSemiJoinRule(this);
      }
  
      /** Defines an operand tree for the given classes. */
      default Config withOperandFor(Class<? extends Intersect> intersectClass) {
        return withOperandSupplier(b -> b.operand(intersectClass).anyInputs())
            .as(Config.class);
      }
    }
  }
  