[postgis-users] 'postgis.backend' is already set

Regina Obe lr at pcorp.us
Tue May 30 01:45:25 PDT 2017

It's a symptom that you have a mix of two PostGIS libraries in your db.

Common causes are:

1) Postgis_SFCGAL older version is installed:

If for example you installed postgis_sfcgal, make sure you upgraded that.  

In 2.1.3 this would have been installed with scripts (not extensions).
Best bet in that case would be to use the uninstall_sfcgal.sql script which is located in contrib/postgis/2.1

And then reinstall using CREATE EXTENSION postgis_sfcgal;

2) The other cause for this is if you installed the legacy.sql file.  You'll need to rerun using the newer legacy.sql packaged with 2.3.2.
3) Postgis topology - I don't think an older PostGIS topology makes any direct references to postgis, so shouldn't cause this issue, but still best to keep this one up to date.

Hope that helps,
PostGIS PSC Member

-----Original Message-----
From: postgis-users [mailto:postgis-users-bounces at lists.osgeo.org] On Behalf Of Arnaud L.
Sent: Tuesday, May 30, 2017 3:43 AM
To: PostGIS Users Discussion <postgis-users at lists.osgeo.org>
Subject: [postgis-users] 'postgis.backend' is already set

Hi all !

After upgrading to Postgis 2.2 (from 2.1.3 I believe), my server log is filled with these messages :

"WARNING 'postgis.backend' is already set and cannot be changed until you reconnect"

I have read some discussions about this message and the closed trac ticket as well, but they all concern upgrade problems (i.e. upgrade fails because of this message).
In my case the upgrade did not fail and my PostGIS runs perfectly fine, appart from this message.
Is it a symptom that something is going bad on my server ? How can I get rid of it ?

OS : Windows Server 2013 64 bits
PostGreSQL : PostgreSQL 9.5.3, compiled by Visual C++ build 1800, 64-bit PostGIS (installed via stack builder) : POSTGIS="2.3.2 r15302"
GEOS="3.6.1-CAPI-1.10.1 r4317" PROJ="Rel. 4.9.1, 04 March 2015"
GDAL="GDAL 2.1.3, released 2017/20/01" LIBXML="2.7.8" LIBJSON="0.12" RASTER

Thanks !

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