[Qgis-developer] QGIS Multi-threaded Rendering

Martin Dobias wonder.sk at gmail.com
Fri Jan 10 22:08:11 PST 2014

Hi Denis

I have just tested with one postgis layer being loaded twice. Turning
editing mode on/off worked smoothly as expected. Could you please try
to track down in what cases it crashes? For example:
- does it happen only with postgis layers?
- must be the layer loaded multiple times in order to crash?
- what if rendering is not turned on when turning on editing mode?

Also, a backtrace would be useful...


On Fri, Jan 10, 2014 at 9:34 PM, Denis Rouzaud <denis.rouzaud at gmail.com> wrote:
> Hi Martin,
> I noticed that QGIS crashes (with the multi-threaded rendering) when you
> turn editing mode on for a layer if this layer exists several times in the
> legend (i.e. the same layer is loaded several times with different styles or
> whatever).
> I observed this at least for postgres.
> Cheers,
> Denis
> On 07. 01. 14 22:23, Andreas Neumann wrote:
>> Hi Martin,
>> I tested it and can confirm that the PostgreSQL pooling works fine and
>> fast now.
>> I see more than 4 Postgis connections though. But maybe these
>> connections are from other plugins using Postgis connections as well.
>> Good to see progress!
>> Thanks,
>> Andreas
>> Am 06.01.2014 13:31, schrieb Martin Dobias:
>>> Hi Andreas
>>> On Fri, Dec 13, 2013 at 8:31 PM, Andreas Neumann <a.neumann at carto.net>
>>> wrote:
>>>> Hi Martin,
>>>> I guess I am also running into the PostgreSQL issue. In general my
>>>> PostgreSQL based projects with many layers freeze after a very short
>>>> time, while the SpatiaLite based projects work very nicely.
>>>> Too many PostgreSQL connections? Can we limit the PostgreSQL connections
>>>> or can you better re-use existing connections?
>>> A quick followup - today I have pushed some changes that introduce a
>>> connection pool for PostgreSQL. This should remove the problem with
>>> too many connections. It limits the maximum number of concurrent
>>> connections from one QGIS instance to four. Also, when the connections
>>> are not used for some time, they get closed to save resources (right
>>> now it is after one minute).
>>> Please test and let me know if things work better now.
>>> I will probably also look at pooling of SpatiaLite connections - right
>>> now the queries within SQLite are serialized, so within one SpatiaLite
>>> database you will not see any performance gain with parallel
>>> rendering.
>>> Regards
>>> Martin
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