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I am trying to use some Geography functions, but I am getting an error that (all) functions are not existing. I have checked other Stackexchange posts (e.g. this one), but the solutions did not work for me.

Since no function is available, I assume that something is wrong with the geography tables. I am using POSTGIS 2.0.1, therefore the geography functions should be supported.

database# select postgis_full_version(); 
POSTGIS="2.0.1 r9979" GEOS="3.3.5-CAPI-1.7.5" PROJ="Rel. 4.8.0, 6 March 2012" GDAL="GDAL
1.9.1, released 2012/05/15" LIBXML="2.7.3" LIBJSON="UNKNOWN" TOPOLOGY RASTER

I can see the geography tables in the database and the database owner also owns the geography tables.

 public   | geography_columns | view     | developer
 public   | geometry_columns  | view     | developer
 public   | raster_columns    | view     | developer
 public   | raster_overviews  | view     | developer

What could cause the error below?

function st_collect(geography) does not exist
LINE 1: SELECT ST_xMin(ST_Collect(location)) AS id, ST_xMax(ST_Colle...
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
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1 Answer 1

up vote 3 down vote accepted

According to www.postgis.org/docs/ST_Collect,

ST_Collect — Return a specified ST_Geometry value from a collection of other geometries.

(emphasis mine) but it seems your location column is of type geography.

Perhaps you need to convert the geography to a geometry via casting:

St_Collect (location::geometry)
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Indeed, only a small subset of functions are implemented for geography. For all others, just cast, as suggested here. –  Paul Ramsey Mar 28 '14 at 7:05
Thank you for your answers. The hint regarding geography vs. geometry reminded me that I put geography=True in the GeoDjango model. –  neurix Mar 28 '14 at 17:56
If you want geography back you need to cast back. So ST_Collect(location::geometry)::geography –  LR1234567 Apr 5 '14 at 4:24

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