[mapguide-internals] PATCH: GwsQueryEngine chooses incorrect join algorithm for joins involving SDF/SHP sources

[GIS4U]

Nice find, thanks for posting the change.

Code change makes sense to me based on what I read.

Jonathon

On Wed, Dec 14, 2011 at 10:10 AM, Bruce Dechant
<bruce.dechant at autodesk.com>wrote:

> Jackie,
>
> The patch looks good.
> This will be a big improvement when using SDF/SHP for joins - nice work!
>
> Thanks,
> Bruce
>
> -----Original Message-----
> From: mapguide-internals-bounces at lists.osgeo.org [mailto:
> mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Jackie Ng
> Sent: Wednesday, December 14, 2011 9:00 AM
> To: mapguide-internals at lists.osgeo.org
> Subject: [mapguide-internals] PATCH: GwsQueryEngine chooses incorrect join
> algorithm for joins involving SDF/SHP sources
>
> Hi All,
>
> I have attached a patch for ticket #1888 (GwsQueryEngine evaluates
> incorrect join algorithm for joins involving SDF/SHP sources)
>
> http://trac.osgeo.org/mapguide/ticket/1888
>
> Simply put, the reason Feature Joins can perform really terrible for joins
> involving SDF or SHP files is because sortability is a critical factor in
> join algorithm selection, and under the existing code the SDF and SHP
> providers both fail the sortability check, which gives us the worst choices
> in join algorithms.
>
> This check is wrong because the two providers can actually output sorted
> query results via the FdoIExtendedSelect command, but that command only
> allows sorting on one property.
>
> So the sortability check has been updated in this patch. A side of the
> join is now considered sortable if:
>
>  1. It supports standard select ordering -OR-  2. It supports the
> FdoIExtendedSelect command (or
> SdfIExtendedSelect/ShpIExtendedSelect) and we're only joining on one
> property.
>
> The existing code already takes advantage of extended select w/ ordering
> if available so nothing needs to be done there.
>
> Please review. Thanks
>
> - Jackie
>
> --
> View this message in context:
> http://osgeo-org.1803224.n2.nabble.com/PATCH-GwsQueryEngine-chooses-incorrect-join-algorithm-for-joins-involving-SDF-SHP-sources-tp7093987p7093987.html
> Sent from the MapGuide Internals mailing list archive at Nabble.com.
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