/**
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.PipelineOp;
import com.bigdata.bop.engine.QueryEngine;
import com.bigdata.rdf.sparql.ast.ASTBase;
import com.bigdata.rdf.sparql.ast.IQueryNode;
import com.bigdata.rdf.sparql.ast.QueryHints;
import com.bigdata.rdf.sparql.ast.QueryRoot;
import com.bigdata.rdf.sparql.ast.eval.AST2BOpContext;
/**
* Query hint marks the operator as requiring "atOnce" evaluation. All solutions
* will be buffered by the {@link QueryEngine} before the operator is evaluated.
* When it is evaluated, it will receive all solutions in a single invocation of
* that operator. However, the solutions MAY appear in multiple chunks since the
* {@link QueryEngine} does not guarantee that the chunk will be merged before
* the operator is invoked. This query hint is allowed in any scope. The hint is
* transferred as an annotation onto all query plan operators generated from the
* annotated scope.
* <p>
* Note: The "atOnce" hint is basically turned into <code>NOT(PIPELINED)</code>.
*
* @see PipelineOp.Annotations#PIPELINED
*/
final class AtOnceHint extends AbstractBooleanQueryHint {
protected AtOnceHint() {
super(QueryHints.AT_ONCE, !PipelineOp.Annotations.DEFAULT_PIPELINED);
}
@Override
public void handle(final AST2BOpContext context, final QueryRoot queryRoot,
final QueryHintScope scope, final ASTBase op, final Boolean value) {
if (op instanceof IQueryNode) {
/*
* Note: This is set on the queryHint Properties object and then
* transferred to the pipeline operator when it is generated.
*/
_setQueryHint(context, scope, op, PipelineOp.Annotations.PIPELINED,
!value);
}
// if (QueryHintScope.Query.equals(scope)) {
//
// /*
// * Also stuff the query hint on the global context for things
// * which look there.
// */
//
// conditionalSetGlobalProperty(context,
// PipelineOp.Annotations.PIPELINED, !value);
//
// }
}
}