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https://issues.apache.org/jira/browse/JENA-111?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13098278#comment-13098278
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Andy Seaborne commented on JENA-111:
------------------------------------
For reference, the full possible stack of modifiers possible in a single level
of SPARQL query is:
Limit/Offset
Distinct/reduce
project
OrderBy
Bindings
having
select expressions
group
but, by using subSELECTs, you can write any sequence you want.
SELECT DISTINCT ?x
{
?x :p 123 .
} ORDER BY ?x LIMIT 2
(slice _ 2
(distinct
(project (?x)
(order (?x)
(bgp (triple ?x :p 123))))))
> Improving TopN optimization in case of an intermediate OpModifier
> -----------------------------------------------------------------
>
> Key: JENA-111
> URL: https://issues.apache.org/jira/browse/JENA-111
> Project: Jena
> Issue Type: Improvement
> Components: ARQ
> Reporter: Sara Magliacane
> Assignee: Paolo Castagna
> Priority: Minor
> Labels: arq, optimization
> Attachments: topk_project.patch
>
>
> In the TopN optimization (Jena-89) it would be useful to handle also the
> case in which there are some other OpModifiers (I think they are the only
> category of Ops that can be in that position in the tree) between Slice and
> Order By, for example OpProject:
> (slice _1
> (project ?s ...
> (order by <condition>
> ->
> (project ?s ...
> (top 1 <condition>
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