/**
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.IPredicate;
import com.bigdata.rdf.sparql.ast.ASTBase;
import com.bigdata.rdf.sparql.ast.QueryHints;
import com.bigdata.rdf.sparql.ast.QueryRoot;
import com.bigdata.rdf.sparql.ast.StatementPatternNode;
import com.bigdata.rdf.sparql.ast.eval.AST2BOpContext;
/**
* Query hint for turning the controlling the #of access paths to sample when
* making a decision between a SCAN+FILTER or PARALLEL SUBQUERY plan for a named
* or default graph access path.
*
* FIXME Unit test. This one is a bit tricky. It gets attached as an AST
* annotation which is transferred to the {@link IPredicate} when that is
* generated. When it comes time to generate the join operator, the property on
* the {@link IPredicate} is checked for the annotation.
* <p>
* This is also true for {@link AccessPathScanAndFilterHint}.
*/
final class AccessPathSampleLimitHint extends AbstractIntQueryHint {
protected AccessPathSampleLimitHint() {
super(QueryHints.ACCESS_PATH_SAMPLE_LIMIT,
QueryHints.DEFAULT_ACCESS_PATH_SAMPLE_LIMIT);
}
@Override
public void handle(final AST2BOpContext context, final QueryRoot queryRoot,
final QueryHintScope scope, final ASTBase op, final Integer value) {
if (op instanceof StatementPatternNode) {
_setAnnotation(context, scope, op, getName(), value);
}
}
}