/**
* 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.engine.join;
import org.apache.jena.graph.Node ;
import org.apache.jena.sparql.core.Var ;
import org.apache.jena.sparql.engine.binding.Binding ;
/** Internal operations in support of join algorithms. */
class JoinLib {
/** Control stats output / development use */
static final boolean JOIN_EXPLAIN = false;
// No hash key marker.
public static final Object noKeyHash = new Object() ;
public static final long nullHashCode = 5 ;
public static long hash(Var v, Node x) {
long h = 17;
if ( v != null )
h = h ^ v.hashCode();
if ( x != null )
h = h ^ x.hashCode();
return h;
}
public static Object hash(JoinKey joinKey, Binding row) {
long x = 31 ;
boolean seenJoinKeyVar = false ;
// Neutral to order in the set.
for ( Var v : joinKey ) {
Node value = row.get(v) ;
long h = nullHashCode ;
if ( value != null ) {
seenJoinKeyVar = true ;
h = hash(v, value) ;
} else {
// In join key, not in row.
}
x = x ^ h ;
}
if ( ! seenJoinKeyVar )
return noKeyHash ;
return x ;
}
}