/*
 * 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.phoenix.expression.function;

import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.phoenix.expression.Expression;
import org.apache.phoenix.expression.aggregator.Aggregator;
import org.apache.phoenix.expression.aggregator.DecimalStddevSampAggregator;
import org.apache.phoenix.expression.aggregator.DistinctValueWithCountClientAggregator;
import org.apache.phoenix.expression.aggregator.DistinctValueWithCountServerAggregator;
import org.apache.phoenix.expression.aggregator.StddevSampAggregator;
import org.apache.phoenix.parse.FunctionParseNode.Argument;
import org.apache.phoenix.parse.FunctionParseNode.BuiltInFunction;
import org.apache.phoenix.schema.types.PDataType;
import org.apache.phoenix.schema.types.PDecimal;

/**
 * Built-in function for {@code STDDEV_SAMP(<expression>) } aggregate function
 * @since 1.2.1
 */
@BuiltInFunction(name = StddevSampFunction.NAME,
    args = { @Argument(allowedTypes = { PDecimal.class }) })
public class StddevSampFunction extends DistinctValueWithCountAggregateFunction {
  public static final String NAME = "STDDEV_SAMP";

  public StddevSampFunction() {

  }

  public StddevSampFunction(List<Expression> childern) {
    super(childern);
  }

  @Override
  public Aggregator newServerAggregator(Configuration conf) {
    return new DistinctValueWithCountServerAggregator(conf);
  }

  @Override
  public DistinctValueWithCountClientAggregator newClientAggregator() {
    if (children.get(0).getDataType() == PDecimal.INSTANCE) {
      // Special Aggregators for DECIMAL datatype for more precision than double
      return new DecimalStddevSampAggregator(children, getAggregatorExpression().getSortOrder());
    }
    return new StddevSampAggregator(children, getAggregatorExpression().getSortOrder());
  }

  @Override
  public String getName() {
    return NAME;
  }

  @Override
  public PDataType getDataType() {
    return PDecimal.INSTANCE;
  }
}
