On Sun, Jun 5, 2016 at 12:29 AM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> Michael Paquier <michael.paqu...@gmail.com> writes:
>> This is still failing:
>> =# select indexdef from pg_catalog.pg_indexes where indexdef is not NULL;
>> ERROR:  XX000: cache lookup failed for index 2619
>> LOCATION:  pg_get_indexdef_worker, ruleutils.c:1054
>> Do we want to improve at least the error message?
> Maybe we should just make the function silently return NULL if the OID
> doesn't refer to an index relation.  There's precedent for that sort
> of behavior ...

For views it is simply returned "Not a view", and for rules that's
"-". All the others behave like similarly to indexes:
=# select pg_get_constraintdef(0);
ERROR:  XX000: cache lookup failed for constraint 0
=# select pg_get_triggerdef(0);
ERROR:  XX000: could not find tuple for trigger 0
=# select pg_get_functiondef(0);
ERROR:  XX000: cache lookup failed for function 0
=# select pg_get_viewdef(0);
 Not a view
(1 row)
=# select pg_get_ruledef(0);
(1 row)

So yes we could just return NULL for all of them, or make them throw
an error. Anyway, my vote goes for a HEAD-only change, and just throw
NULL... This way an application still has the option to fallback to
something else with a CASE at SQL level without using plpgsql to catch
the error.

Also, I have not monitored the code much regarding some code paths
that rely on the existing rules, but I would imagine that there are
things depending on the current behavior as well.

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