com.bigdata.bop.join.HashJoinAnnotations Maven / Gradle / Ivy
/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
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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 Aug 14, 2011
*/
package com.bigdata.bop.join;
import com.bigdata.bop.IVariable;
/**
* Annotations for hash joins.
*
* @author Bryan Thompson
* @version $Id$
*/
public interface HashJoinAnnotations {
/**
* The {@link IVariable[]} specifying the join variables (required). The
* order of the entries is used when forming the as-bound keys for the hash
* table. Duplicate elements and null elements are not permitted.
*
* Note: The source solutions presented to a hash join MUST have bindings
* for the {@link #JOIN_VARS} in order to join (source solutions can still
* be passed on as optionals, but they will not join unless the join
* variables are not bound).
*
* Note: If no join variables are specified, then the join will consider the
* N x M cross product, filtering for solutions which join. This is very
* expensive when compared to a hash join. Whenever possible you should
* identify one or more variables which must be bound for the join and
* specify those as the join variables.
*/
String JOIN_VARS = HashJoinAnnotations.class.getName() + ".joinVars";
/**
* When non-null, the {@link IVariable} which will be bound to
* true iff there is at least one solution for a
* {@link JoinTypeEnum#Exists} hash join.
*
* Note: This supports the bridge between the evaluation of the (NOT) EXISTS
* graph pattern and the processing whether or not the "EXISTS" graph
* pattern was successful, which is encoded on the "ask variable."
*/
String ASK_VAR = HashJoinAnnotations.class.getName() + ".askVar";
// /**
// * The maximum number of solutions that will be considered before a hash
// * join without any join variables is failed.
// *
// * The purpose of this annotation is to identify hash joins which are doing
// * too much work because they lack any join variables.
// */
// String NO_JOIN_VARS_LIMIT = HashJoinAnnotations.class.getName()
// + ".noJoinVarsLimit";
/**
* TODO Annotation and query hint for this.
*
* @see UnconstrainedJoinException
*/
long DEFAULT_NO_JOIN_VARS_LIMIT = Long.MAX_VALUE;
/**
* Boolean flag to be set when we do not want to return the variables
* defined by the {#JVMHashIndexOp.Annotations.SELECT} annotation, but
* instead calculate the DISTINCT projection over the join variables.
* This is the approach that we use for many subgroups, where we project
* in the distinct variables (typically: exactly the join variables),
* execute the inner group, and finally rejoin with the whole set of
* variables in the end.
*/
final String OUTPUT_DISTINCT_JVs =
HashJoinAnnotations.class.getName() + ".outputDistinctJVs";
}