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.fun;
  
  import org.apache.calcite.sql.SqlFunctionCategory;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.type.OperandTypes;
  import org.apache.calcite.sql.type.ReturnTypes;
  
  /**
   * The {@code GROUP_ID()} function.
   *
   * <p>Accepts no arguments. The {@code GROUP_ID()} function distinguishes duplicate groups
   * resulting from a GROUP BY specification. It is useful in filtering out duplicate groupings
   * from the query result.
   *
   * <p>This function is not defined in the SQL standard; our implementation is
   * consistent with Oracle.
   *
   * <p>If n duplicates exist for a particular grouping, then {@code GROUP_ID()} function returns
   * numbers in the range 0 to n-1.
   *
   * <p>Some examples are in {@code agg.iq}.
   */
  class SqlGroupIdFunction extends SqlAbstractGroupFunction {
    SqlGroupIdFunction() {
      super("GROUP_ID", SqlKind.GROUP_ID, ReturnTypes.BIGINT, null,
          OperandTypes.NILADIC, SqlFunctionCategory.SYSTEM);
    }
  }
  