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.type.SqlTypeUtil;
  import org.apache.calcite.sql.validate.SqlValidator;
  import org.apache.calcite.sql.validate.SqlValidatorNamespace;
  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 sort 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: order operation list
   * </ul>
   */
  public class SqlWithinGroupOperator extends SqlBinaryOperator {
  
    public SqlWithinGroupOperator() {
      super("WITHIN GROUP", SqlKind.WITHIN_GROUP, 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 GROUP");
      final SqlWriter.Frame orderFrame =
          writer.startList(SqlWriter.FrameTypeEnum.ORDER_BY_LIST, "(", ")");
      writer.keyword("ORDER BY");
      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);
      final SqlOperator operator = flat.aggregateCall.getOperator();
      if (!operator.isAggregator()) {
        throw validator.newValidationError(call, RESOURCE.withinGroupNotAllowed(operator.getName()));
      }
  
      for (SqlNode order : requireNonNull(flat.orderList)) {
        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) {
      SqlCall inner = call.operand(0);
      final SqlOperator operator = inner.getOperator();
      if (!operator.isAggregator()) {
        throw validator.newValidationError(call, RESOURCE.withinGroupNotAllowed(operator.getName()));
      }
  
      if (inner.getOperator().getKind() == SqlKind.PERCENTILE_DISC
          || inner.getOperator().getKind() == SqlKind.PERCENTILE_CONT) {
        // We first check the percentile call operands, and then derive the correct type using
        // PercentileDiscCallBinding (See CALCITE-5230).
        SqlCallBinding opBinding =
            new PercentileDiscCallBinding(validator, scope, inner, getCollationColumn(call));
        inner.getOperator().checkOperandTypes(opBinding, true);
        RelDataType ret = inner.getOperator().inferReturnType(opBinding);
        validator.setValidatedNodeType(inner, ret);
        return ret;
      } else {
        return validateOperands(validator, scope, call);
      }
    }
  
    private static SqlNode getCollationColumn(SqlCall call) {
      return ((SqlNodeList) call.operand(1)).get(0);
    }
  
    /**
     * Used for PERCENTILE_DISC return type inference.
     */
    public static class PercentileDiscCallBinding extends SqlCallBinding {
      private final SqlNode collationColumn;
  
      private PercentileDiscCallBinding(SqlValidator validator,
          SqlValidatorScope scope,
          SqlCall call,
          SqlNode collation) {
        super(validator, scope, call);
        this.collationColumn = collation;
      }
  
      @Override public RelDataType getCollationType() {
        final RelDataType type = SqlTypeUtil.deriveType(this, collationColumn);
        final SqlValidatorNamespace namespace = super.getValidator().getNamespace(collationColumn);
        return namespace != null ? namespace.getType() : type;
      }
    }
  }
  