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.CorrelationId;
  import org.apache.calcite.util.Litmus;
  
  import com.google.common.collect.ImmutableSet;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.ArrayDeque;
  import java.util.Deque;
  import java.util.Set;
  
  /**
   * Visitor that checks that every {@link RelNode} in a tree is valid.
   *
   * @see RelNode#isValid(Litmus, RelNode.Context)
   */
  public class RelValidityChecker extends RelVisitor
      implements RelNode.Context {
    private int invalidCount;
    private final Deque<RelNode> stack = new ArrayDeque<>();
  
    @Override public Set<CorrelationId> correlationIds() {
      final ImmutableSet.Builder<CorrelationId> builder =
          ImmutableSet.builder();
      for (RelNode r : stack) {
        builder.addAll(r.getVariablesSet());
      }
      return builder.build();
    }
  
    @Override public void visit(RelNode node, int ordinal,
        @Nullable RelNode parent) {
      try {
        stack.push(node);
        if (!node.isValid(Litmus.THROW, this)) {
          ++invalidCount;
        }
        super.visit(node, ordinal, parent);
      } finally {
        stack.pop();
      }
    }
  
    public int invalidCount() {
      return invalidCount;
    }
  }
  