id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
17785	PostgreSQL Introspection: get_relations() broken after drop column	Thomas Güttler	nobody	"Hi,

if a column gets dropped postgreSQL does not update the attnum of columns which have a higher attnum:

{{{

# oid: select oid from pg_class where relname='modwork_buchungskreis';

modwork_eins_d=> select attrelid, attname, atttypid,  attnum from pg_attribute where attrelid = 149923 order by attnum; attrelid |           attname            | atttypid | attnum 
----------+------------------------------+----------+--------
   149923 | tableoid                     |       26 |     -7
   149923 | cmax                         |       29 |     -6
   149923 | xmax                         |       28 |     -5
   149923 | cmin                         |       29 |     -4
   149923 | xmin                         |       28 |     -3
   149923 | ctid                         |       27 |     -1
   149923 | id                           |     1043 |      1
   149923 | name                         |     1043 |      2
   149923 | ........pg.dropped.3........ |        0 |      3
   149923 | ........pg.dropped.4........ |        0 |      4
   149923 | default                      |       16 |      5
   149923 | beschreibung                 |     1043 |      6
   149923 | archiv                       |     1043 |      7
   149923 | email_sender_id              |     1043 |      8


}}}

BTW, the same bug is in django/db/backends/postgresql/introspection.py

Patch attached. I think it is overkill to write a unittest for this. Please let me know if you want a test.
"	Bug	closed	Database layer (models, ORM)	1.3	Normal	fixed	psycopg2 introspection	hv	Ready for checkin	1	0	0	0	0	0