/*
* 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 com.hp.hpl.jena.graph.Node ;
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.expr.nodevalue.XSDFuncOp ;
import com.hp.hpl.jena.sparql.function.FunctionEnv ;
import com.hp.hpl.jena.sparql.sse.writers.WriterExpr ;
import com.hp.hpl.jena.sparql.util.ExprUtils ;
public class AggAvg extends AggregatorBase
{
// ---- AVG(?var)
private Expr expr ;
public AggAvg(Expr expr) { this.expr = expr ; }
@Override
public Aggregator copy(Expr expr) { return new AggAvg(expr) ; }
// XQuery/XPath Functions&Operators suggests zero
// SQL suggests null.
private static final NodeValue noValuesToAvg = NodeValue.nvZERO ; // null
@Override
public String toString() { return "avg("+ExprUtils.fmtSPARQL(expr)+")" ; }
@Override
public String toPrefixString() { return "(avg "+WriterExpr.asString(expr)+")" ; }
@Override
public Accumulator createAccumulator()
{
return new AccAvg(expr) ;
}
@Override
public final Expr getExpr() { return expr ; }
@Override
public Node getValueEmpty() { return NodeValue.toNode(noValuesToAvg) ; }
@Override
public int hashCode() { return HC_AggAvg ^ expr.hashCode() ; }
@Override
public boolean equals(Object other)
{
if ( this == other ) return true ;
if ( ! ( other instanceof AggAvg ) ) return false ;
AggAvg a = (AggAvg)other ;
return expr.equals(a.expr) ;
}
// ---- Accumulator
private static class AccAvg extends AccumulatorExpr
{
// Non-empty case but still can be nothing because the expression may be undefined.
private NodeValue total = noValuesToAvg ;
private int count = 0 ;
static final boolean DEBUG = false ;
public AccAvg(Expr expr) { super(expr) ; }
@Override
protected void accumulate(NodeValue nv, Binding binding, FunctionEnv functionEnv)
{
if ( DEBUG ) System.out.println("avg: "+nv) ;
if ( nv.isNumber() )
{
count++ ;
if ( total == noValuesToAvg )
total = nv ;
else
total = XSDFuncOp.numAdd(nv, total) ;
}
else
{
//ARQ.getExecLogger().warn("Evaluation error: avg() on "+nv) ;
throw new ExprEvalException("avg: not a number: "+nv) ;
}
if ( DEBUG ) System.out.println("avg: ("+total+","+count+")") ;
}
@Override
protected void accumulateError(Binding binding, FunctionEnv functionEnv)
{}
@Override
public NodeValue getAccValue()
{
if ( count == 0 ) return noValuesToAvg ;
if ( super.errorCount != 0 )
//throw new ExprEvalException("avg: error in group") ;
return null ;
NodeValue nvCount = NodeValue.makeInteger(count) ;
return XSDFuncOp.numDivide(total, nvCount) ;
}
}
}