/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
licenses@blazegraph.com
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on Nov 27, 2011
*/
package com.bigdata.rdf.sparql.ast.hints;
import com.bigdata.bop.solutions.HTreeDistinctBindingSetsOp;
import com.bigdata.rdf.sparql.ast.ASTBase;
import com.bigdata.rdf.sparql.ast.QueryBase;
import com.bigdata.rdf.sparql.ast.QueryHints;
import com.bigdata.rdf.sparql.ast.QueryRoot;
import com.bigdata.rdf.sparql.ast.eval.AST2BOpContext;
/**
* Query hint for turning the {@link HTreeDistinctBindingSetsOp} on/off.
*
* TODO This can only be used enable/disable the native distinct solutions both
* on a query wide basis (via {@link AST2BOpContext}). However, it should be
* possible to enable/disable this on a (sub-)select basis (by interpreting the
* AST annotation when we are generating the query plan. When supporting this
* more selective application, write a unit test which verifies that the native
* distinct annotation is correctly interpreted when it appears on a
* {@link QueryBase}.
*
* TODO The same is true of {@link QueryHints#NATIVE_DISTINCT_SPO} and several
* other similar "analytic" hints. However, this is not possible (or is more
* difficult) when the native versus JVM semantics of the operation span
* non-local operators (i.e., named subqueries with their non-local includes).
*/
final class NativeDistinctQueryHint extends AbstractBooleanQueryHint {
protected NativeDistinctQueryHint() {
super(QueryHints.NATIVE_DISTINCT_SOLUTIONS,
QueryHints.DEFAULT_NATIVE_DISTINCT_SOLUTIONS);
}
@Override
public void handle(final AST2BOpContext context, final QueryRoot queryRoot,
final QueryHintScope scope, final ASTBase op, final Boolean value) {
if (scope == QueryHintScope.Query) {
context.nativeDistinctSolutions = value;
return;
}
// if (op instanceof QueryBase) {
//
// super.attach(context, scope, op, value);
//
// }
throw new QueryHintException(scope, op, getName(), value);
}
}