As of PostGIS 2.3, the postgis extension was changed to no longer allow relocation.
All function calls within the extension are now schema qualified.
While this change fixed some issues with database restore, it created the issue of
if you installed PostGIS in a schema other than the one you wanted to
it is not intuitive how to move it to a different schema. Luckily there is a way to do this.
For this exercise, I will install PostGIS in the default schema and then demonstrate how to move
it into another schema location.
You can run these steps using psql or pgAdmin or any other PostgreSQL tool you want.
The error ‘postgis.backend’ is already set comes up every so often in PostGIS mailing list.
The issue arises often during or after an upgrade. I’ll go over causes for this I am aware of and how to fix.
The question goes something like this
After upgrading to Postgis 2.3 from 2.1, my server log is
filled with these messages :
“WARNING ‘postgis.backend’ is already set and cannot be changed until
This raster question comes up quite a bit on PostGIS mailing lists and stack overflow and the best answer often involves
the often forgotten
ST_Reclass function that has existed since PostGIS 2.0.
People often resort to the much slower though more flexible
ST_MapAlgebra or dumping out
their rasters as Pixel valued polygons they then filter
with WHERE val > 90,
ST_Reclass does the same thing but orders of magnitude faster.
PostGIS 2.2.0 came out this month, and the SFCGAL extension that offers advanced 3D and volumetric support, in addition to some extended 2D functions like
ST_ApproximateMedialAxis became a standard PostgreSQL extension
and seems to be a fairly popular extension.
I’ve seen several reports on GIS Stack Exchange of people trying to install PostGIS SFCGAL and getting things such as
ERROR: could not open extension control file /Applications/Postgres.app/Contents/Versions/9.5/share/postgresql/extension/postgis_sfcgal.control
as in this question: SFCGAL in PostGIS problem.
There are two main causes for this:
I’ve been asked this question in some shape or form at least 3 times, mostly from people puzzled why they get this error.
The last iteration went something like this:
I can’t use
ST_AsPNG when doing something like
Gives error: Warning: pg_query(): Query failed: ERROR: rt_raster_to_gdal: Could not load the output GDAL driver.