/*
* 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.jena.sparql.expr.aggregate;
import java.util.HashSet ;
import java.util.Set ;
import org.apache.jena.sparql.engine.binding.Binding ;
import org.apache.jena.sparql.expr.Expr ;
import org.apache.jena.sparql.expr.ExprEvalException ;
import org.apache.jena.sparql.expr.ExprLib ;
import org.apache.jena.sparql.expr.NodeValue ;
import org.apache.jena.sparql.function.FunctionEnv ;
/** Accumulator that passes down every value of an expression */
public abstract class AccumulatorExpr implements Accumulator
{
private final Set<NodeValue> values ;
private long accCount = 0 ;
protected long errorCount = 0 ;
private final Expr expr ;
private final boolean makeDistinct;
protected AccumulatorExpr(Expr expr, boolean makeDistinct) {
this.expr = expr;
// Not all subclsses use th wmachinary here to handled DISTINCT.
// SAMPLE(DISTINCT) and COUNT(DISTINCT *) are different.
this.makeDistinct = makeDistinct ;
this.values = makeDistinct ? new HashSet<>() : null ;
}
@Override
final public void accumulate(Binding binding, FunctionEnv functionEnv) {
NodeValue nv = ExprLib.evalOrNull(expr, binding, functionEnv);
if ( nv != null ) {
if ( makeDistinct ) {
if ( values.contains(nv) )
return ;
values.add(nv) ;
}
try {
accumulate(nv, binding, functionEnv);
accCount++;
return;
}
catch (ExprEvalException ex) {}
// Drop to error case.
}
accumulateError(binding, functionEnv);
errorCount++;
}
// COUNT(?v) and COUNT(DISTINCT ?v) are different
// errors of the expression/variable do not cause an aggregate eval error.
// SAMPLE, SAMPLE(DISTINCT) are different
// treat errors as "just another value" and tries to return a defined value if any have been seen.
@Override
public NodeValue getValue() {
if ( errorCount == 0 )
return getAccValue();
return null;
}
/** Get the count of accumulated values */
protected long getAccCount() { return accCount ; }
/** Called if no errors to get the accumulated result */
protected abstract NodeValue getAccValue() ;
/** Called when the expression beeing aggregated evaluates OK.
* Can throw ExprEvalException - in which case the accumulateError is called */
protected abstract void accumulate(NodeValue nv, Binding binding, FunctionEnv functionEnv) ;
/** Called when an evaluation of the expression causes an error
* or when the accumulation step throws ExprEvalException
*/
protected abstract void accumulateError(Binding binding, FunctionEnv functionEnv) ;
}