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/*
 * 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 com.hazelcast.org.apache.calcite.rex;

import com.hazelcast.org.apache.calcite.rel.type.RelDataType;

import java.util.Objects;

/**
 * Reference to a range of columns.
 *
 * This construct is used only during the process of translating a
 * {@link com.hazelcast.org.apache.calcite.sql.SqlNode SQL} tree to a
 * {@link com.hazelcast.org.apache.calcite.rel.RelNode rel}/{@link RexNode rex}
 * tree. Regular {@link RexNode rex} trees do not contain this
 * construct.
 *
 * While translating a join of EMP(EMPNO, ENAME, DEPTNO) to DEPT(DEPTNO2,
 * DNAME) we create RexRangeRef(DeptType,3) 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.
 *
 * Suppose we later create a reference to the DNAME field of this
 * RexRangeRef; it will return a {@link RexInputRef}(5,Integer),
 * and the {@link com.hazelcast.org.apache.calcite.rex.RexRangeRef} will disappear.
 */
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 accept(RexVisitor visitor) {
    return visitor.visitRangeRef(this);
  }

  public  R accept(RexBiVisitor visitor, P arg) {
    return visitor.visitRangeRef(this, arg);
  }

  @Override public boolean equals(Object obj) {
    return this == obj
        || obj instanceof RexRangeRef
        && type.equals(((RexRangeRef) obj).type)
        && offset == ((RexRangeRef) obj).offset;
  }

  @Override public int hashCode() {
    return Objects.hash(type, offset);
  }

  @Override public String toString() {
    return "offset(" + offset + ")";
  }
}