/*
* 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.io.DataInput;
import java.io.IOException;
import java.util.Arrays;
import java.util.Comparator;
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.visitor.ExpressionVisitor;
import org.apache.phoenix.schema.PDataType;
import org.apache.phoenix.schema.tuple.Tuple;
/**
*
* Base class for aggregate functions that calculate an aggregation
* using a single {{@link Aggregator}
*
*
* @since 0.1
*/
abstract public class SingleAggregateFunction extends AggregateFunction {
private static final List<Expression> DEFAULT_EXPRESSION_LIST = Arrays.<Expression>asList(LiteralExpression.newConstant(1, true));
protected boolean isConstant;
private Aggregator aggregator;
/**
* Sort aggregate functions with nullable fields last. This allows us not to have to store trailing null values.
* Within non-nullable/nullable groups, put fixed width values first since we can access those more efficiently
* (i.e. we can skip over groups of them in-mass instead of reading the length of each one to skip over as
* required by a variable length value).
*/
public static final Comparator<SingleAggregateFunction> SCHEMA_COMPARATOR = new Comparator<SingleAggregateFunction>() {
@Override
public int compare(SingleAggregateFunction o1, SingleAggregateFunction o2) {
boolean isNullable1 = o1.isNullable();
boolean isNullable2 = o2.isNullable();
if (isNullable1 != isNullable2) {
return isNullable1 ? 1 : -1;
}
isNullable1 = o1.getAggregatorExpression().isNullable();
isNullable2 = o2.getAggregatorExpression().isNullable();
if (isNullable1 != isNullable2) {
return isNullable1 ? 1 : -1;
}
// Ensures COUNT(1) sorts first TODO: unit test for this
boolean isConstant1 = o1.isConstantExpression();
boolean isConstant2 = o2.isConstantExpression();
if (isConstant1 != isConstant2) {
return isConstant1 ? 1 : -1;
}
PDataType r1 = o1.getAggregator().getDataType();
PDataType r2 = o2.getAggregator().getDataType();
if (r1.isFixedWidth() != r2.isFixedWidth()) {
return r1.isFixedWidth() ? -1 : 1;
}
return r1.compareTo(r2);
}
};
protected SingleAggregateFunction() {
this(DEFAULT_EXPRESSION_LIST, true);
}
public SingleAggregateFunction(List<Expression> children) {
this(children, children.get(0) instanceof LiteralExpression);
}
private SingleAggregateFunction(List<Expression> children, boolean isConstant) {
super(children);
this.isConstant = children.get(0) instanceof LiteralExpression;
this.aggregator = newClientAggregator();
}
public boolean isConstantExpression() {
return isConstant;
}
@Override
public PDataType getDataType() {
return children.get(0).getDataType();
}
public Expression getAggregatorExpression() {
return children.get(0);
}
public Aggregator getAggregator() {
return aggregator;
}
@Override
public boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr) {
return getAggregator().evaluate(tuple, ptr);
}
/**
* Create the aggregator to do server-side aggregation.
* The data type of the returned Aggregator must match
* the data type returned by {@link #newClientAggregator()}
* @param conf HBase configuration.
* @return the aggregator to use on the server-side
*/
abstract public Aggregator newServerAggregator(Configuration conf);
/**
* Create the aggregator to do client-side aggregation
* based on the results returned from the aggregating
* coprocessor. The data type of the returned Aggregator
* must match the data type returned by {@link #newServerAggregator(Configuration)}
* @return the aggregator to use on the client-side
*/
public Aggregator newClientAggregator() {
return newServerAggregator(null);
}
public Aggregator newServerAggregator(Configuration config, ImmutableBytesWritable ptr) {
Aggregator agg = newServerAggregator(config);
agg.aggregate(null, ptr);
return agg;
}
public void readFields(DataInput input, Configuration conf) throws IOException {
super.readFields(input);
aggregator = newServerAggregator(conf);
}
@Override
public boolean isNullable() {
return true;
}
protected SingleAggregateFunction getDelegate() {
return this;
}
@Override
public final <T> T accept(ExpressionVisitor<T> visitor) {
SingleAggregateFunction function = getDelegate();
List<T> l = acceptChildren(visitor, visitor.visitEnter(function));
T t = visitor.visitLeave(function, l);
if (t == null) {
t = visitor.defaultReturn(function, l);
}
return t;
}
}