/*
* 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 com.hp.hpl.jena.sparql.expr.aggregate;
import java.util.HashSet ;
import java.util.Set ;
import com.hp.hpl.jena.sparql.engine.binding.Binding ;
import com.hp.hpl.jena.sparql.expr.Expr ;
import com.hp.hpl.jena.sparql.expr.ExprEvalException ;
import com.hp.hpl.jena.sparql.expr.NodeValue ;
import com.hp.hpl.jena.sparql.function.FunctionEnv ;
/** Accumulator that only passes down unique values of an expression (the first encountered) */
abstract class AccumulatorDistinctExpr implements Accumulator
{
// Better?? record a large hash.
private final Set<NodeValue> values = new HashSet<NodeValue>() ;
private long errorCount = 0 ;
private long count = 0 ;
private final Expr expr ;
protected AccumulatorDistinctExpr(Expr expr)
{
this.expr = expr ;
}
@Override
final public void accumulate(Binding binding, FunctionEnv functionEnv)
{
try {
NodeValue nv = expr.eval(binding, functionEnv) ;
if ( values.contains(nv) )
return ;
values.add(nv) ;
accumulateDistinct(nv, binding, functionEnv) ;
count++ ;
} catch (ExprEvalException ex)
{
errorCount++ ;
accumulateError(binding, functionEnv) ;
}
}
// Count(DISTINCT ?v) is different
@Override
public NodeValue getValue()
{
if ( errorCount == 0 )
return getAccValue() ;
return null ;
}
protected long getErrorCount() { return errorCount ; }
protected abstract NodeValue getAccValue() ;
protected abstract void accumulateDistinct(NodeValue nv, Binding binding, FunctionEnv functionEnv) ;
protected abstract void accumulateError(Binding binding, FunctionEnv functionEnv) ;
}