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From "Andy Seaborne (JIRA)" <>
Subject [jira] [Commented] (JENA-111) Improving TopN optimization in case of an intermediate OpModifier
Date Sun, 11 Sep 2011 19:36:09 GMT


Andy Seaborne commented on JENA-111:

There is a bug in the transformation (it fails to check there is a LIMIT at all).  fixed.

Then adding code for case 4 (which is case 3 in the code) seems to work.  Please review the
current TransformTopN

Test from the patch applied to the source code except slice_order_to_topn_0{5,6,7}a() which
are false tests (they are for case 3 above which isn't a valid optimization).

Note that the case of plain project over order is commented out in TransformTopN - if uncommented.
I'm getting warnings about unclosed iterators - which suggests something is not passing down
,close() calls.    Warnings are from "Solution Sequence" / "Limit 3" (recorded as JENA-114).

TestOptimizer.slice_order_to_topn_01a() is comments out because of this.

> Improving TopN optimization in case of an intermediate OpModifier
> -----------------------------------------------------------------
>                 Key: JENA-111
>                 URL:
>             Project: Jena
>          Issue Type: Improvement
>          Components: ARQ
>            Reporter: Sara Magliacane
>            Assignee: Paolo Castagna
>            Priority: Minor
>              Labels: arq, optimization
>         Attachments: JENA-111_ARQ_r1165795.patch, 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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