/*
 * 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.eigenbase.rex;

import org.eigenbase.reltype.*;

/**
 * Reference to a range of columns.
 *
 * <p>This construct is used only during the process of translating a {@link
 * org.eigenbase.sql.SqlNode SQL} tree to a {@link org.eigenbase.rel.RelNode
 * rel}/{@link RexNode rex} tree. <em>Regular {@link RexNode rex} trees do not
 * contain this construct.</em></p>
 *
 * <p>While translating a join of EMP(EMPNO, ENAME, DEPTNO) to DEPT(DEPTNO2,
 * DNAME) we create <code>RexRangeRef(DeptType,3)</code> to represent the pair
 * of columns (DEPTNO2, DNAME) which came from DEPT. The type has 2 columns, and
 * therefore the range represents columns {3, 4} of the input.</p>
 *
 * <p>Suppose we later create a reference to the DNAME field of this
 * RexRangeRef; it will return a <code>{@link RexInputRef}(5,Integer)</code>,
 * and the {@link org.eigenbase.rex.RexRangeRef} will disappear.</p>
 */
public class RexRangeRef extends RexNode {
  //~ Instance fields --------------------------------------------------------

  private final RelDataType type;
  private final int offset;

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

  /**
   * Creates a range reference.
   *
   * @param rangeType Type of the record returned
   * @param offset    Offset of the first column within the input record
   */
  RexRangeRef(
      RelDataType rangeType,
      int offset) {
    this.type = rangeType;
    this.offset = offset;
  }

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

  public RelDataType getType() {
    return type;
  }

  public int getOffset() {
    return offset;
  }

  public <R> R accept(RexVisitor<R> visitor) {
    return visitor.visitRangeRef(this);
  }
}

// End RexRangeRef.java