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;
  
  import org.apache.calcite.rel.core.Aggregate;
  import org.apache.calcite.rel.core.AggregateCall;
  import org.apache.calcite.rel.core.Filter;
  import org.apache.calcite.rel.core.Join;
  import org.apache.calcite.rel.core.Project;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.rex.RexUtil;
  import org.apache.calcite.util.Util;
  
  import com.google.common.collect.Ordering;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.Comparator;
  import java.util.function.BiConsumer;
  import java.util.function.Predicate;
  
  /**
   * Utilities concerning relational expressions.
   */
  public class RelNodes {
    /** Comparator that provides an arbitrary but stable ordering to
     * {@link RelNode}s. */
    public static final Comparator<RelNode> COMPARATOR =
        new RelNodeComparator();
  
    /** Ordering for {@link RelNode}s. */
    public static final Ordering<RelNode> ORDERING = Ordering.from(COMPARATOR);
  
    private RelNodes() {}
  
    /** Compares arrays of {@link RelNode}. */
    public static int compareRels(RelNode[] rels0, RelNode[] rels1) {
      int c = Integer.compare(rels0.length, rels1.length);
      if (c != 0) {
        return c;
      }
      for (int i = 0; i < rels0.length; i++) {
        c = COMPARATOR.compare(rels0[i], rels1[i]);
        if (c != 0) {
          return c;
        }
      }
      return 0;
    }
  
    /** Returns whether a tree of {@link RelNode}s contains a match for a
     * {@link RexNode} finder. */
    public static boolean contains(RelNode rel,
        Predicate<AggregateCall> aggPredicate, RexUtil.RexFinder finder) {
      try {
        findRex(rel, finder, aggPredicate, (relNode, rexNode) -> {
          throw Util.FoundOne.NULL;
        });
        return false;
      } catch (Util.FoundOne e) {
        return true;
      }
    }
  
    /** Searches for expressions in a tree of {@link RelNode}s. */
    // TODO: a new method RelNode.accept(RexVisitor, BiConsumer), with similar
    // overrides to RelNode.accept(RexShuttle), would be better.
    public static void findRex(RelNode rel, RexUtil.RexFinder finder,
        Predicate<AggregateCall> aggPredicate,
        BiConsumer<RelNode, @Nullable RexNode> consumer) {
      if (rel instanceof Filter) {
        Filter filter = (Filter) rel;
        try {
          filter.getCondition().accept(finder);
        } catch (Util.FoundOne e) {
          consumer.accept(filter, (RexNode) e.getNode());
        }
      }
      if (rel instanceof Project) {
        Project project = (Project) rel;
        for (RexNode node : project.getProjects()) {
          try {
            node.accept(finder);
          } catch (Util.FoundOne e) {
            consumer.accept(project, (RexNode) e.getNode());
          }
        }
      }
      if (rel instanceof Join) {
        Join join = (Join) rel;
        try {
          join.getCondition().accept(finder);
        } catch (Util.FoundOne e) {
          consumer.accept(join, (RexNode) e.getNode());
        }
      }
      if (rel instanceof Aggregate) {
        Aggregate aggregate = (Aggregate) rel;
        for (AggregateCall aggregateCall : aggregate.getAggCallList()) {
          if (aggPredicate.test(aggregateCall)) {
            consumer.accept(aggregate, null);
          }
        }
      }
      for (RelNode input : rel.getInputs()) {
        findRex(input, finder, aggPredicate, consumer);
      }
    }
  
    /** Arbitrary stable comparator for {@link RelNode}s. */
    private static class RelNodeComparator implements Comparator<RelNode> {
      @Override public int compare(RelNode o1, RelNode o2) {
        // Compare on field count first. It is more stable than id (when rules
        // are added to the set of active rules).
        final int c =
            Integer.compare(o1.getRowType().getFieldCount(),
                o2.getRowType().getFieldCount());
        if (c != 0) {
          return -c;
        }
        return Integer.compare(o1.getId(), o2.getId());
      }
    }
  }
  