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.sql;
  
  import org.apache.calcite.sql.type.InferTypes;
  import org.apache.calcite.sql.type.OperandTypes;
  import org.apache.calcite.sql.type.ReturnTypes;
  import org.apache.calcite.sql.type.SqlTypeTransforms;
  
  /**
   * The {@code MEASURE} wraps an expression in the {@code SELECT} clause and tags
   * it as a measure.
   *
   * <p>For example, the SQL '{@code x + 1 AS MEASURE y}' becomes the
   * {@code SqlNode} AST '{@code AS(MEASURE(x + 1), y)}'.
   *
   * <p>The operator is not used in {@code RexNode}.
   */
  public class SqlMeasureOperator extends SqlInternalOperator {
    /**
     * Creates a MEASURE operator.
     */
    public SqlMeasureOperator() {
      super("MEASURE", SqlKind.MEASURE, 20, true,
          ReturnTypes.ARG0.andThen(SqlTypeTransforms.TO_MEASURE),
          InferTypes.RETURN_TYPE, OperandTypes.ANY);
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public SqlSyntax getSyntax() {
      return SqlSyntax.INTERNAL;
    }
  
    @Override public void unparse(SqlWriter writer, SqlCall call, int leftPrec,
        int rightPrec) {
      // AS should have checked for MEASURE wrapper around first argument
      throw new UnsupportedOperationException();
    }
  }
  