/*
* 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.Arrays;
import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.phoenix.expression.Expression;
import org.apache.phoenix.expression.LiteralExpression;
import org.apache.phoenix.expression.aggregator.Aggregator;
import org.apache.phoenix.expression.aggregator.CountAggregator;
import org.apache.phoenix.expression.aggregator.LongSumAggregator;
import org.apache.phoenix.parse.FunctionParseNode.Argument;
import org.apache.phoenix.parse.FunctionParseNode.BuiltInFunction;
import org.apache.phoenix.schema.PDataType;
import org.apache.phoenix.util.SchemaUtil;
/**
*
* Built-in function for COUNT(<expression>) aggregate function,
* for example COUNT(foo), COUNT(1), COUNT(*)
*
*
* @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() {
@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);
}
}