[mapguide-internals] What MapGuide does during database schema discovery?

[Zac Spitzer]

surely the native FDO provider is going to perform far better than OGR?


On Wed, Mar 19, 2014 at 9:54 PM, Gabriele Monfardini
<gabrimonfa at gmail.com>wrote:

> Hi all,
>
> I had a PostgreSQL/Postgis database with some schemas and many tables.
> I'm connecting to it using MapGuide 2.5.2, OGR provider and a recompiled
> gdal/ogr library to support PostgreSQL.
>
> All is working fine except for one thing.
> The first time that a map that use this db is opened it takes tens of
> seconds to appear.
> After the first time, the same map is opened in 3-4 seconds as it should.
>
> Investigating this issue the problem seems to be in schema discovery since
> purging cached schema information from maestro triggers again the slow
> start.
>
> Analyzing database log I've found that MapGuide seems to try to evaluate
> the extent of each geometry table in the database (brutally querying SELECT
> Extent(the_geom) on all of them).
>
> And we happen to have a few very complicated views, defined from several
> other views, which are used in a totally unrelated project and never
> in MapGuide. Querying the extent of those views eats a lot of seconds.
>
> Tuning the views is not really an option since evaluating the extent is
> somewhat unexpected on them.
>
> Thus my questions are the following:
>
>    1. What stats is MapGuide collecting on all tables? Are there anything
>    configurable?
>    2. Are there any way to manually exclude problematic tables?
>    In PostGIS <2 I can drop the rows related to those tables from
>    geometry_columns, since MapGuide use geometry_columns, but in PostGIS 2+
>    this is no more possible.
>    I've seen also that another possible workaround is to set the SRID for
>    problematic tables to undefined, but again this is not always possible.
>    Also I've not understood why the SRID does make this difference...
>    3. Why is extent needed? And if really needed why don't use
>    ST_Estimated_Extent (or ST_EstimatedExtent in PostGIS 2.1+) to have a
>    quicker response from the database?
>
>
> Best regards,
>
> Gabriele Monfardini
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>



-- 
Zac Spitzer
+61 405 847 168