com.bigdata.rdf.sparql.ast.optimizers

Class ASTFlattenUnionsOptimizer

java.lang.Object

com.bigdata.rdf.sparql.ast.optimizers.ASTFlattenUnionsOptimizer

All Implemented Interfaces:

IASTOptimizer

public class ASTFlattenUnionsOptimizer
extends Object
implements IASTOptimizer

Flatten nested UNIONs whenever possible.

 UNION(A,B,C) := UNION(A,UNION(B,C)) -or- UNION(UNION(A,B),C))
 

Note: This must run before the ASTEmptyGroupOptimizer in order to eliminate certain UNION/group combinations.

Note: The bigdata SPARQL parser no longer produces this nested UNION construction. However, it is possible that other SPARQL parsers or hand construction can still produce this nesting pattern, in which case this optimizer will flatten out that pattern.

Version:

$Id: ASTFlattenUnionsOptimizer.java 5314 2011-10-12 12:51:13Z thompsonbry $

Author:

Bryan Thompson

Constructor Summary

Constructors

Constructor and Description
ASTFlattenUnionsOptimizer()

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

ASTFlattenUnionsOptimizer

public ASTFlattenUnionsOptimizer()

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.