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.rel.type.RelDataType;
  import org.apache.calcite.sql.type.OperandTypes;
  import org.apache.calcite.sql.type.ReturnTypes;
  import org.apache.calcite.sql.validate.SqlValidator;
  import org.apache.calcite.sql.validate.SqlValidatorScope;
  import org.apache.calcite.sql.validate.SqlValidatorUtil;
  
  import static org.apache.calcite.util.Static.RESOURCE;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * An operator that applies a distinct operation before rows are included in an
   * aggregate function.
   *
   * <p>Operands are as follows:
   *
   * <ul>
   * <li>0: a call to an aggregate function ({@link SqlCall})
   * <li>1: expressions to make distinct
   * </ul>
   */
  public class SqlWithinDistinctOperator extends SqlBinaryOperator {
    public SqlWithinDistinctOperator() {
      super("WITHIN DISTINCT", SqlKind.WITHIN_DISTINCT, 100, true,
          ReturnTypes.ARG0, null, OperandTypes.ANY_IGNORE);
    }
  
    @Override public void unparse(SqlWriter writer, SqlCall call, int leftPrec,
        int rightPrec) {
      assert call.operandCount() == 2;
      call.operand(0).unparse(writer, 0, 0);
      writer.keyword("WITHIN DISTINCT");
      final SqlWriter.Frame orderFrame =
          writer.startList(SqlWriter.FrameTypeEnum.GROUP_BY_LIST, "(", ")");
      call.operand(1).unparse(writer, 0, 0);
      writer.endList(orderFrame);
    }
  
    @Override public void validateCall(
        SqlCall call,
        SqlValidator validator,
        SqlValidatorScope scope,
        SqlValidatorScope operandScope) {
      assert call.getOperator() == this;
      assert call.operandCount() == 2;
      final SqlValidatorUtil.FlatAggregate flat =
          SqlValidatorUtil.flatten(call);
      if (!flat.aggregateCall.getOperator().isAggregator()) {
        throw validator.newValidationError(call,
            RESOURCE.withinDistinctNotAllowed(
                flat.aggregateCall.getOperator().getName()));
      }
      for (SqlNode order : requireNonNull(flat.distinctList)) {
        requireNonNull(validator.deriveType(scope, order));
      }
      validator.validateAggregateParams(flat.aggregateCall, flat.filter,
          flat.distinctList, flat.orderList, scope);
    }
  
    @Override public RelDataType deriveType(
        SqlValidator validator,
        SqlValidatorScope scope,
        SqlCall call) {
      // Validate type of the inner aggregate call
      return validateOperands(validator, scope, call);
    }
  }
  