Re: partition tree inspection functions

On Mon, Oct 01, 2018 at 04:27:57PM +0900, Amit Langote wrote:
> Yeah, maybe there is no reason to delay proceeding with
> pg_partition_children which provides a useful functionality.

So, I have been looking at your patch, and there are a couple of things
which could be improved.

Putting the new function pg_partition_children() in partition.c is a
bad idea I think. So instead I think that we should put that in a
different location, say utils/adt/partitionfuncs.c.

+ TupleDescInitEntry(tupdesc, (AttrNumber) 1, "relid",
+ REGCLASSOID, -1, 0);
+ TupleDescInitEntry(tupdesc, (AttrNumber) 2, "parentid",
+ REGCLASSOID, -1, 0);
REGCLASSOID is used mainly for casting, so instead let's use OIDOID like
any other system function.

+ values[2] = psprintf("%d", level);
+ values[3] = psprintf("%c", relkind == RELKIND_PARTITIONED_TABLE ?
+ 'f' :
+ 't');
Using Datum objects is more elegant in this context.

isleaf is not particularly useful as it can just be fetched with a join
on pg_class/relkind. So I think that we had better remove it.

I have cleaned up a bit tests, removing duplicates and most of the
things which touched the size of relations to have something more
portable.

We could have a flavor using a relation name in input with qualified
names handled properly (see pg_get_viewdef_name for example), not sure
if that's really mandatory so I left that out. I have also added some
comments here and there. The docs could be worded a bit better still.

My result is the patch attached. What do you think?
--
Michael