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https://issues.apache.org/jira/browse/JENA-780?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14616421#comment-14616421
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ASF subversion and git services commented on JENA-780:
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Commit 459f069355bbe2419db9e628a472532652ac37b6 in jena's branch
refs/heads/master from [~rvesse]
[ https://git-wip-us.apache.org/repos/asf?p=jena.git;h=459f069 ]
Merge branch 'eliminate-assignments-jena3' (JENA-780)
Adds support for the new assignment inlining optimization to the master
branch. This optimisation is off by default but can be enabled by the
context switch optInlineAssignments and made aggressive using the context
switch optInlineAssignmentsAggressive
> Single use extend expressions could be substituted directly for their later
> usage
> ---------------------------------------------------------------------------------
>
> Key: JENA-780
> URL: https://issues.apache.org/jira/browse/JENA-780
> Project: Apache Jena
> Issue Type: Improvement
> Components: ARQ, Optimizer
> Affects Versions: Jena 2.12.0
> Reporter: Rob Vesse
> Assignee: Rob Vesse
> Priority: Minor
> Attachments: JENA-780.patch
>
>
> This RFE is a follow on from JENA-779, the query with a sub-optimal plan
> there uses a {{BIND}} to create a value which is then only used once in a
> subsequent filter.
> Actually that query uses it twice but I think the general approach I am
> trying to describe in this RFE bears consideration. In this case it seems
> like it would be possible to substitute the extend expression for the bound
> variable in the filter expression.
> Simplified variant of original query such that the bound value is only used
> once:
> {noformat}
> SELECT DISTINCT ?uri
> {
> { ?uri ?p ?o }
> UNION
> {
> ?sub ?p ?uri
> FILTER(isIRI(?uri))
> }
> BIND(str(?uri) as ?s)
> FILTER(STRSTARTS(?s, "http://";))
> }
> {noformat}
> Rewritten query:
> {noformat}
> SELECT DISTINCT ?domainName
> {
> { ?uri ?p ?o }
> UNION
> {
> ?sub ?p ?uri
> FILTER(isIRI(?uri))
> }
> FILTER(STRSTARTS(str(?uri), "http://";))
> }
> {noformat}
> Which avoids an extend expression whose value is only used once and will
> ultimately be thrown away.
> From a {{Transform}} standpoint this is likely awkward to implement in a pure
> transform since it requires knowledge about the query structure above the
> {{FILTER}} i.e. whether the bound variable is used elsewhere and so would
> need to use before and after visitors to track that additional state but I
> think this is a feasible optimisation.
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