Peter Eisentraut <pete...@gmx.net> writes: > On sön, 2010-09-19 at 09:41 +0000, saer...@hotmail.com wrote: >> The Sequence view in the information schema is incomplete. It does not >> return a Sequence's maximum_value, minimum_value or increment. Please >> complete the view.
> This is known and documented: > http://www.postgresql.org/docs/8.4/static/infoschema-sequences.html > Should still be fixed eventually, of course. I think the difficulty is in the fact that you can't join to a sequence whose name isn't predetermined. In the past we've speculated about creating a single catalog or view containing all sequences' parameters, so that information_schema.sequences could be implemented with a join to that. However, there's never been any movement on that, and it seems less than trivial to do. What about inventing a function to extract a sequence's parameters? Perhaps something like pg_sequence_parameter(seq regclass, colname text) returns bigint which would do an appropriate permissions check and then fetch the named column. (This could actually be implemented in a line or two in plpgsql, but I think we want it in C because information_schema shouldn't depend on plpgsql.) This would work OK for all the bigint columns, and we could cheat a bit for the boolean columns by returning 0 or 1. You couldn't fetch the sequence_name column this way, but that's okay with me --- we don't maintain that anyway. Given that, the sequence view would include outputs like CAST(pg_sequence_parameter(c.oid, 'max_value') AS cardinal_number) AS maximum_value, The main objection I can see to this is that fetching multiple column values would involve multiple accesses to the sequence. But it's not clear that a solution based on a single view would be any better performance-wise. Another possibility, if we had LATERAL, would be a function that takes just the sequence OID and returns all its parameters as a row. But again, if we want to do it that way then fixing the view will involve waiting for a complex feature that might or might not show up anytime soon. Or maybe we could implement that function, call it like this CAST((pg_sequence_parameters(c.oid)).max_value AS cardinal_number) AS maximum_value, and plan on optimizing the view when we get LATERAL. regards, tom lane -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
