[Qgis-developer] PostGIS provider estimated extent

[Jürgen E. Fischer]

Hi Jeremy,

On Mon, 15. Mar 2010 at 12:56:23 +1300, Jeremy Palmer wrote:
> I was just wondering about the purpose of r13014 which implemented a
> "setNoExtentEstimate" flag for a PostgreSQL connection. 

> I have a little issue with this when used in conjunction with the new use
> estimated metadata provider option.  Because the PostgreSQL connections are
> pooled for the postgres provider, it is possible to have the connection
> "hasNoExtentEstimate" flag indefinitely set when you can't get a result back
> from estimated_extent function for a table (see line 2777 of
> qgspostgresprovider.cpp).

Yes.  That was the problem.  Trying to use estimates without actually having
any caused the query to fail.  That also invalidates all open cursors.  The
idea was that either all or no tables have estimates.   In the latter case the
very first query would fail and subsequent queries wouldn't try to use
estimates.


Jürgen

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