/*
* 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.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.phoenix.expression.Expression;
import org.apache.phoenix.expression.aggregator.Aggregator;
import org.apache.phoenix.expression.aggregator.DistinctCountClientAggregator;
import org.apache.phoenix.expression.aggregator.DistinctValueWithCountServerAggregator;
import org.apache.phoenix.parse.FunctionParseNode.Argument;
import org.apache.phoenix.parse.FunctionParseNode.BuiltInFunction;
import org.apache.phoenix.schema.PDataType;
import org.apache.phoenix.schema.tuple.Tuple;
import org.apache.phoenix.util.SchemaUtil;
/**
*
* Built-in function for COUNT(distinct <expression>) aggregate function,
*
*
* @since 1.2.1
*/
@BuiltInFunction(name=DistinctCountAggregateFunction.NAME, args= {@Argument()} )
public class DistinctCountAggregateFunction extends DelegateConstantToCountAggregateFunction {
public static final String NAME = "DISTINCT_COUNT";
public static final String NORMALIZED_NAME = SchemaUtil.normalizeIdentifier(NAME);
public final static byte[] ZERO = PDataType.LONG.toBytes(0L);
public final static byte[] ONE = PDataType.LONG.toBytes(1L);
public DistinctCountAggregateFunction() {
}
public DistinctCountAggregateFunction(List<Expression> childExpressions) {
this(childExpressions, null);
}
public DistinctCountAggregateFunction(List<Expression> childExpressions,
CountAggregateFunction delegate) {
super(childExpressions, delegate);
assert childExpressions.size() == 1;
}
@Override
public int hashCode() {
return isConstantExpression() ? 0 : super.hashCode();
}
/**
* The COUNT function never returns null
*/
@Override
public boolean isNullable() {
return false;
}
@Override
public boolean equals(Object obj) {
if (this == obj) return true;
if (obj == null) return false;
if (getClass() != obj.getClass()) return false;
DistinctCountAggregateFunction other = (DistinctCountAggregateFunction)obj;
return (isConstantExpression() && other.isConstantExpression()) || children.equals(other.getChildren());
}
@Override
public PDataType getDataType() {
return PDataType.LONG;
}
@Override
public DistinctCountClientAggregator newClientAggregator() {
return new DistinctCountClientAggregator(getAggregatorExpression().getSortOrder());
}
@Override
public Aggregator newServerAggregator(Configuration conf) {
return new DistinctValueWithCountServerAggregator(conf);
}
@Override
public boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr) {
// TODO: optimize query plan of this to run scan serially for a limit of one row
if (!super.evaluate(tuple, ptr)) {
ptr.set(ZERO); // If evaluate returns false, then no rows were found, so result is 0
} else if (isConstantExpression()) {
ptr.set(ONE); // Otherwise, we found one or more rows, so a distinct on a constant is 1
}
return true; // Always evaluates to a LONG value
}
@Override
public String getName() {
return NAME;
}
@Override
public Aggregator newServerAggregator(Configuration config, ImmutableBytesWritable ptr) {
DistinctCountClientAggregator clientAgg = newClientAggregator();
clientAgg.aggregate(null, ptr);
return new DistinctValueWithCountServerAggregator(config, clientAgg);
}
}