[QGIS-Developer] Reduced compatibility with old PosgreSQL/PostGIS databases in v. 4.0.0

[Stefanos Natsis]

Hi,

One breaking change I'm aware of in QGIS 4 is that we've used the `CREATE
TABLE IF NOT EXISTS` idiom for the `qgis_projects` table (for storing
projects in the database) which was introduced in PostgreSQL 9.1

Best,
Stefanos

On Tue, 31 Mar 2026 at 15:55, Even Rouault via QGIS-Developer <
qgis-developer at lists.osgeo.org> wrote:

> Carlo,
>
> you're conflating two different things:
>
> - PostgreSQL & PostGIS version support in GDAL.  It might still semi work
> for you with dropped supported version by chance/accident.
>
> - PostgreSQL & PostGIS version support in QGIS PostgreSQL provider.
> Looking quickly at git log, I don't see anything explicit abut dropping
> them. I suppose that support for those older versions broke by accident or
> wasn't explicitly mentionned.
>
> In any case those ancient versions aren't supported, have likely unfixed
> security issues, and it would be hard for us to test against them.
>
> So use older QGIS versions if you really need to stick with your ancient
> PostgreSQL & PostGIS version. There's hardly no chance you can convince us
> (at least me for the code I'm responsible of) to bring back support for them
>
> Even
> Le 31/03/2026 à 14:44, Carlo A. Bertelli (Charta s.r.l.) via
> QGIS-Developer a écrit :
>
> I understand that GDAL declares
>
>> Starting with GDAL 3.9, only PostgreSQL >= 9 and PostGIS >= 2 are
>> supported.
>
> but version 3.44 still can open layers from a v. 8.4 database and PostGIS
> 1.5.
> Now version 4 does not open layers from this database.
> GDAL v. 3.12.3 per se can open these layers, ogrinfo works well, ogr2ogr
> lets me upload data from files to the same database.
> What happened with the new version? I cannot even change parameters per
> table. Is there a solution for this?
> Unfortunately I cannot change the database nor upgrade it, even if I would
> like very much.
> c
>
> --
> --------------------------------------------------------------------------
> Carlo A. Bertelli
>    Charta servizi e sistemi per il territorio e la storia ambientale srl
>           Dipendenze del palazzo Doria,
>           vc. alla Chiesa della Maddalena 9/2 16124      Genova (Italy)
>           tel./fax +39(0)10 2475439  +39 0108566195  mobile:+39 393
> 1590711
>    e-mail: bertelli at chartasrl.eu      http://www.chartasrl.eu
> --------------------------------------------------------------------------
>
>
>
>
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