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
25476	Use pg_catalog tables to introspect constraints	heasus	nobody	"Using inspectdb of Django1.8.4 with psycopg2 2.6.1 to import an existing db, get_constraints() attempts to read table constraints. It exits here parsing foreign keys with the traceback:

{{{
File ""/home/www/db/lib/python3.4/site-packages/django/db/backends/postgresql_psycopg2/introspection.py"", line 171, in get_constraints
""foreign_key"": tuple(used_cols[0].split(""."", 1)) if kind.lower() == ""foreign key"" else None,
IndexError: list index out of range
}}}

The array of columns returned from the db is populated:

{{{
SELECT
kc.constraint_name,
kc.column_name,
c.constraint_type,
array(SELECT table_name::text || '.' || column_name::text
FROM information_schema.constraint_column_usage
WHERE constraint_name = kc.constraint_name)
FROM information_schema.key_column_usage AS kc
JOIN information_schema.table_constraints AS c ON
kc.table_schema = c.table_schema AND
kc.table_name = c.table_name AND
kc.constraint_name = c.constraint_name
WHERE
kc.table_schema = 'public' AND
kc.table_name = 'things'

ORDER BY kc.ordinal_position ASC;
}}}

{{{
constraint_name     | column_name | constraint_type |                array

------------------------+-------------+-----------------+-----------------------

things_pkey | trunk | PRIMARY KEY | {things.trunk,things.c
hild}
things_child_fkey | child | FOREIGN KEY | {children.idx}
things_trunk_fkey | trunk | FOREIGN KEY | {children.idx}
things_pkey | child | PRIMARY KEY | {things.trunk,things.c
hild}
}}}

but empty from cursor.fetchall(): for constraint, column, kind, used_cols in cursor.fetchall(). A script using psycopg2 directly does not exhibit this problem. I;ve also tried a current development checkout of django.

This is as far as I've traced this so far and it does not seem to be a known issue."	Cleanup/optimization	closed	Database layer (models, ORM)	dev	Normal	fixed	psycopg2 fetchall inspectdb permissions	gagangupt16@… marcos@…	Accepted	1	0	0	1	0	0