[fdo-users] PostGIS FDO Provider performance issues

[Dan Stoica]

My bet is that "something else" is the look up for the property in the logical/physical collections of properties.
E.g. for 20 properties in the class the provider will do aprox. 2,000,000 wide string comparisons for 200,000 rows.
Actually it is 4 million because of IsNull() calls. This is the performance killer.

The problem has been solved for rdbms providers by caching the properties in the order they are fetched (at the first fetch). So the property will be found either in the same position (after a IsNull) or in the next slot. This is equivalent to fetching a property by index rather by name.

The implementation is in GenericRdbms:
FdoRdbmsFeatureReader::Property2ColNameChar()

Hope this helps,
Dan.

-----Original Message-----
From: fdo-users-bounces at lists.osgeo.org [mailto:fdo-users-bounces at lists.osgeo.org] On Behalf Of Zac Spitzer
Sent: Wednesday, June 11, 2008 3:03 AM
To: FDO Users Mail List
Subject: Re: [fdo-users] PostGIS FDO Provider performance issues

I would agree it's too much overhead, as this happening with Oracle as
well ( anyone else seen
this happen with another db?) perhaps there is something else in play.

How many rows are fetched by the client? Fetching one row at a time is
slower than returning blocks of 100 rows..

Using mapguide, it's always the mapguide process (ie FDO) and not the
database which is showing the high cpu

z



On Wed, Jun 11, 2008 at 4:56 PM, Carl Jokl <carl.jokl at keynetix.com> wrote:
>
> It is true that there is extra overhead in performing the conversion or going
> through FDO but I think it is fair to say that having PostGIS 16 to 20 times
> slower on the same data is more of a performance hit than would have been
> expected.
> --
> View this message in context: http://www.nabble.com/PostGIS-FDO-Provider-performance-issues-tp17756475p17771210.html
> Sent from the FDO Users mailing list archive at Nabble.com.
>
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> fdo-users mailing list
> fdo-users at lists.osgeo.org
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--
Zac Spitzer -
http://zacster.blogspot.com (My Blog)
+61 405 847 168
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