com.bigdata.rdf.sparql.ast.optimizers

Class ASTServiceNodeOptimizer

java.lang.Object

com.bigdata.rdf.sparql.ast.optimizers.ASTServiceNodeOptimizer

All Implemented Interfaces:

IASTOptimizer

public class ASTServiceNodeOptimizer
extends Object
implements IASTOptimizer

Rewrites the WHERE clause of each query by lifting out ServiceNodes into a named subquery. Recursively rewrites the WHERE clause of any named subquery such that there is no more than one ServiceNode in that subquery by lifting out additional ServiceNodes into new named subqueries.

Note: This rewrite step is useful when it is desirable to run the service once (it is also possible to annotate the ServiceCall operator as PipelineOp.Annotations#PIPELINED := false.

By default, if a ServiceNode appears in any position other than the head of a NamedSubqueryRoot, then it will be invoked once for each chunk of solutions which flows through that part of the query plan.

Version:

$Id: ASTServiceNodeOptimizer.java 6068 2012-03-03 21:34:31Z thompsonbry $ FIXME This has been modified to ONLY apply to BD#SEARCH. It may well be that we want to take this out entirely. Our internal search service runs well when lifted out. However, it might run just as well if we specified it as an "at-once" operator.

Author:

Bryan Thompson

Constructor Summary

Constructors

Constructor and Description
ASTServiceNodeOptimizer()

Method Summary

Methods

Modifier and Type	Method and Description
QueryNodeWithBindingSet	optimize(AST2BOpContext context, QueryNodeWithBindingSet input) Optimize the AST.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ASTServiceNodeOptimizer

public ASTServiceNodeOptimizer()

Method Detail

optimize

public QueryNodeWithBindingSet optimize(AST2BOpContext context,
                               QueryNodeWithBindingSet input)

Description copied from interface: IASTOptimizer

Optimize the AST.

Specified by:

optimize in interface IASTOptimizer

Parameters:

context - The evaluation context.

input - The input to the optimizer, consisting of a queryNode and input binding set.

Returns:

An instance of type QueryNodeWithBindingSet.