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.plan.volcano;
  
  import org.apache.calcite.plan.RelOptRuleOperand;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.util.Litmus;
  
  import java.util.List;
  import java.util.Map;
  
  /**
   * A match of a rule to a particular set of target relational expressions,
   * frozen in time.
   */
  class VolcanoRuleMatch extends VolcanoRuleCall {
    //~ Instance fields --------------------------------------------------------
  
    private String digest;
  
    //~ Constructors -----------------------------------------------------------
  
    /**
     * Creates a <code>VolcanoRuleMatch</code>.
     *
     * @param operand0 Primary operand
     * @param rels     List of targets; copied by the constructor, so the client
     *                 can modify it later
     * @param nodeInputs Map from relational expressions to their inputs
     */
    @SuppressWarnings("method.invocation.invalid")
    VolcanoRuleMatch(VolcanoPlanner volcanoPlanner, RelOptRuleOperand operand0,
        RelNode[] rels, Map<RelNode, List<RelNode>> nodeInputs) {
      super(volcanoPlanner, operand0, rels.clone(), nodeInputs);
      assert allNotNull(rels, Litmus.THROW);
  
      digest = computeDigest();
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public String toString() {
      return digest;
    }
  
    /**
     * Computes a string describing this rule match. Two rule matches are
     * equivalent if and only if their digests are the same.
     *
     * @return description of this rule match
     */
    private String computeDigest() {
      StringBuilder buf =
          new StringBuilder("rule [" + getRule() + "] rels [");
      for (int i = 0; i < rels.length; i++) {
        if (i > 0) {
          buf.append(',');
        }
        buf.append('#').append(rels[i].getId());
      }
      buf.append(']');
      return buf.toString();
    }
  
    /**
     * Recomputes the digest of this VolcanoRuleMatch.
     */
    @Deprecated // to be removed before 2.0
    public void recomputeDigest() {
      digest = computeDigest();
    }
  
    /** Returns whether all elements of a given array are not-null;
     * fails if any are null. */
    private static <E> boolean allNotNull(E[] es, Litmus litmus) {
      for (E e : es) {
        if (e == null) {
          return litmus.fail("was null", (Object) es);
        }
      }
      return litmus.succeed();
    }
  
  }
  