/*******************************************************************************
* Copyright (c) 2013, Salesforce.com, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* Neither the name of Salesforce.com nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
******************************************************************************/
package com.salesforce.phoenix.expression.function;
import java.util.Arrays;
import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import com.salesforce.phoenix.expression.Expression;
import com.salesforce.phoenix.expression.LiteralExpression;
import com.salesforce.phoenix.expression.aggregator.Aggregator;
import com.salesforce.phoenix.expression.aggregator.CountAggregator;
import com.salesforce.phoenix.expression.aggregator.LongSumAggregator;
import com.salesforce.phoenix.parse.FunctionParseNode.Argument;
import com.salesforce.phoenix.parse.FunctionParseNode.BuiltInFunction;
import com.salesforce.phoenix.schema.PDataType;
import com.salesforce.phoenix.util.SchemaUtil;
/**
*
* Built-in function for COUNT(<expression>) aggregate function,
* for example COUNT(foo), COUNT(1), COUNT(*)
*
* @author jtaylor
* @since 0.1
*/
@BuiltInFunction(name=CountAggregateFunction.NAME, args= {@Argument()} )
public class CountAggregateFunction extends SingleAggregateFunction {
public static final String NAME = "COUNT";
public static final List<Expression> STAR = Arrays.<Expression>asList(LiteralExpression.newConstant(1, true));
public static final String NORMALIZED_NAME = SchemaUtil.normalizeIdentifier(NAME);
public CountAggregateFunction() {
}
public CountAggregateFunction(List<Expression> childExpressions) {
super(childExpressions);
}
@Override
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj == null) return false;
if (getClass() != obj.getClass()) return false;
CountAggregateFunction other = (CountAggregateFunction)obj;
return (isConstantExpression() && other.isConstantExpression()) || children.equals(other.getChildren());
}
@Override
public int hashCode() {
return isConstantExpression() ? 0 : super.hashCode();
}
/**
* The COUNT function never returns null
*/
@Override
public boolean isNullable() {
return false;
}
@Override
public PDataType getDataType() {
return PDataType.LONG;
}
@Override
public LongSumAggregator newClientAggregator() {
// Since COUNT can never be null, ensure the aggregator is not nullable.
// This allows COUNT(*) to return 0 with the initial state of ClientAggregators
// when no rows are returned.
return new LongSumAggregator(null) {
@Override
public boolean isNullable() {
return false;
}
};
}
@Override
public Aggregator newServerAggregator(Configuration conf) {
return new CountAggregator();
}
@Override
public String getName() {
return NAME;
}
@Override
public Aggregator newServerAggregator(Configuration config, ImmutableBytesWritable ptr) {
LongSumAggregator sumAgg = newClientAggregator();
sumAgg.aggregate(null, ptr);
return new CountAggregator(sumAgg);
}
}