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.Join;
  import org.apache.calcite.rel.core.JoinRelType;
  import org.apache.calcite.tools.RelBuilder;
  
  /**
   * Rule to convert an
   * {@link org.apache.calcite.rel.core.Join inner join} to a
   * {@link org.apache.calcite.rel.core.Filter filter} on top of a
   * {@link org.apache.calcite.rel.core.Join cartesian inner join}.
   *
   * <p>One benefit of this transformation is that after it, the join condition
   * can be combined with conditions and expressions above the join.
   *
   * <p>The constructor is parameterized to allow any sub-class of
   * {@link org.apache.calcite.rel.core.Join}.
   */
  public abstract class AbstractJoinExtractFilterRule
      extends RelRule<AbstractJoinExtractFilterRule.Config>
      implements TransformationRule {
    /** Creates an AbstractJoinExtractFilterRule. */
    protected AbstractJoinExtractFilterRule(Config config) {
      super(config);
    }
  
    @Override public void onMatch(RelOptRuleCall call) {
      final Join join = call.rel(0);
  
      if (join.getJoinType() != JoinRelType.INNER) {
        return;
      }
  
      if (join.getCondition().isAlwaysTrue()) {
        return;
      }
  
      if (!join.getSystemFieldList().isEmpty()) {
        // FIXME Enable this rule for joins with system fields
        return;
      }
  
      final RelBuilder builder = call.builder();
  
      // NOTE jvs 14-Mar-2006:  See JoinCommuteRule for why we
      // preserve attribute semiJoinDone here.
  
      final RelNode cartesianJoin =
          join.copy(
              join.getTraitSet(),
              builder.literal(true),
              join.getLeft(),
              join.getRight(),
              join.getJoinType(),
              join.isSemiJoinDone());
  
      builder.push(cartesianJoin)
          .filter(join.getCondition());
  
      call.transformTo(builder.build());
    }
  
    /** Rule configuration. */
    public interface Config extends RelRule.Config {
    }
  }
  