Re: partition tree inspection functions

On Fri, Oct 19, 2018 at 06:55:09PM +0900, Amit Langote wrote:
> Yeah, we could make it the responsibility of the callers of
> find_all_inheritors and find_inheritance_children to check relhassubclass
> as an optimization and remove any reference to relhassubclass from
> pg_inherits.c.  Although we can write such a patch, it seems like it'd be
> bigger than the patch to ensure the correct value of relhassubclass for
> indexes, which I just posted on the other thread [1].

And what is present as patch 0001 on this thread has been committed as
55853d6, so we are good for this part.

>> Anyway, it seems that you are right here.  Just setting relhassubclass
>> for partitioned indexes feels more natural with what's on HEAD now.
>> Even if I'd like to see all those hypothetical columns in pg_class go
>> away, that cannot happen without a close lookup at the performance
>> impact.
> 
> Okay, I updated the patch on this thread.

Thanks for the new version.

> Since the updated patch depends on the correct value of relhassubclass
> being set for indexes, this patch should be applied on top of the other
> patch.  I've attached here both.

-       if (!has_subclass(parentrelId))
+       if (get_rel_relkind(parentrelId) != RELKIND_PARTITIONED_INDEX &&
+               !has_subclass(parentrelId))
                return NIL;

You don't need this bit anymore, relhassubclass is now set for
partitioned indexes.

+      ereport(ERROR,
+              (errcode(ERRCODE_WRONG_OBJECT_TYPE),
+               errmsg("\"%s\" is not a table, a foreign table, or an index",
+                      get_rel_name(rootrelid))));
Should this also list "partitioned tables and partitioned indexes"?  The
style is heavy, but that maps with what pgstattuple does..

The tests should include also something for a leaf index when fed to
pg_partition_tree() (in order to control the index names you could just
attach an index to a partition after creating it, but I leave that up to
you).

+ pg_partition_tree(oid)
+       setof record

The change to regclass has not been reflected yet in the documentation
and the implementation, because...

> Another change I made is something Robert and Alvaro seem to agree about
> -- to use regclass instead of oid type as input/output columns.

...  I am in minority here, it feels lonely ;)
--
Michael