core/src/main/java/org/apache/calcite/rex/RexPermutationShuttle.java

/*
 * 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.rex;

import org.apache.calcite.util.Permutation;

/**
 * Visitor which replaces {@link RexLocalRef} objects after the expressions in a
 * {@link RexProgram} have been reordered.
 *
 * @see RexPermuteInputsShuttle
 */
public class RexPermutationShuttle extends RexShuttle {
  //~ Instance fields --------------------------------------------------------

  private final Permutation permutation;

  //~ Constructors -----------------------------------------------------------

  public RexPermutationShuttle(Permutation permutation) {
    this.permutation = permutation;
  }

  //~ Methods ----------------------------------------------------------------

  @Override public RexNode visitLocalRef(RexLocalRef local) {
    final int index = local.getIndex();
    int target = permutation.getTarget(index);
    return new RexLocalRef(
        target,
        local.getType());
  }
}