Geodjango and PostGIS Exception Error

[2059016j@…]

I have connected an existing POSTGIS database and when I run inspectdb I get Exception: Could not find a geometry or geography column for "raster_columns"."extent"

[Tim Graham]

What's the expected result? What's the type of the "extent" column?

[Harm Geerts <hgeerts@…>]

raster_columns is a view, which is part of the postgis extension for postgresql.
Using postgresql-9.2.4 and postgis-2.0.3

# \d
             List of relations
 Schema |       Name        | Type  | Owner 
--------+-------------------+-------+-------
 public | geography_columns | view  | harm
 public | geometry_columns  | view  | harm
 public | raster_columns    | view  | harm
 public | raster_overviews  | view  | harm
 public | spatial_ref_sys   | table | harm

# \d+ raster_columns
                        View "public.raster_columns"
      Column      |        Type        | Modifiers | Storage  | Description 
------------------+--------------------+-----------+----------+-------------
 r_table_catalog  | name               |           | plain    | 
 r_table_schema   | name               |           | plain    | 
 r_table_name     | name               |           | plain    | 
 r_raster_column  | name               |           | plain    | 
 srid             | integer            |           | plain    | 
 scale_x          | double precision   |           | plain    | 
 scale_y          | double precision   |           | plain    | 
 blocksize_x      | integer            |           | plain    | 
 blocksize_y      | integer            |           | plain    | 
 same_alignment   | boolean            |           | plain    | 
 regular_blocking | boolean            |           | plain    | 
 num_bands        | integer            |           | plain    | 
 pixel_types      | text[]             |           | extended | 
 nodata_values    | double precision[] |           | extended | 
 out_db           | boolean[]          |           | extended | 
 extent           | geometry           |           | main     | 
View definition:
 SELECT current_database() AS r_table_catalog, n.nspname AS r_table_schema, 
    c.relname AS r_table_name, a.attname AS r_raster_column, 
    COALESCE(_raster_constraint_info_srid(n.nspname, c.relname, a.attname), ( SELECT st_srid('010100000000000000000000000000000000000000'::geometry) AS st_srid)) AS srid, 
    _raster_constraint_info_scale(n.nspname, c.relname, a.attname, 'x'::bpchar) AS scale_x, 
    _raster_constraint_info_scale(n.nspname, c.relname, a.attname, 'y'::bpchar) AS scale_y, 
    _raster_constraint_info_blocksize(n.nspname, c.relname, a.attname, 'width'::text) AS blocksize_x, 
    _raster_constraint_info_blocksize(n.nspname, c.relname, a.attname, 'height'::text) AS blocksize_y, 
    COALESCE(_raster_constraint_info_alignment(n.nspname, c.relname, a.attname), false) AS same_alignment, 
    COALESCE(_raster_constraint_info_regular_blocking(n.nspname, c.relname, a.attname), false) AS regular_blocking, 
    _raster_constraint_info_num_bands(n.nspname, c.relname, a.attname) AS num_bands, 
    _raster_constraint_info_pixel_types(n.nspname, c.relname, a.attname) AS pixel_types, 
    _raster_constraint_info_nodata_values(n.nspname, c.relname, a.attname) AS nodata_values, 
    _raster_constraint_info_out_db(n.nspname, c.relname, a.attname) AS out_db, 
    _raster_constraint_info_extent(n.nspname, c.relname, a.attname) AS extent
   FROM pg_class c, pg_attribute a, pg_type t, pg_namespace n
  WHERE t.typname = 'raster'::name AND a.attisdropped = false AND a.atttypid = t.oid AND a.attrelid = c.oid AND c.relnamespace = n.oid AND (c.relkind = 'r'::"char" OR c.relkind = 'v'::"char") AND NOT pg_is_other_temp_schema(c.relnamespace);

These views/tables contain metadata about tables/columns using geometric and/or geographic columns.
However they do not contain metadata about themselves so the type lookup always fails.
​https://github.com/django/django/blob/master/django/contrib/gis/db/backends/postgis/introspection.py#L51

[Harm Geerts <hgeerts@…>]

​https://github.com/django/django/pull/1418

[Tim Graham]

Looks reasonable, someone more familiar with GIS will need to review it. Is there any way to add a test for this?

[Claude Paroz]

Comment left on PR.

As for tests, there are examples in tests/inspectdb/tests.py. I'm not absolutely sure it's feasible, but worth looking into.

[Claude Paroz <claude@…>]

In 240886183b022055b5a5115916c7c9766ec55c51:

Fixed #20829 -- Skip postgis metadata tables with introspection

[Claude Paroz <claude@…>]

In a6ac4f90d0d09da884289d6f03df4e4800c8f742:

[1.6.x] Fixed #20829 -- Skip postgis metadata tables with introspection

Backport of 24088618 from master.