Re: Accessing schema data in information schema

Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> How does one get at the missing fields. The only way I know is
> selecting from the sequence, but how does one work this into this
> query? Somehow it seems that these things should be stored in a real
> system catalog.

Yeah. I've occasionally toyed with the idea that sequences should be
rows in a single catalog instead of independent tables as they are now.
This would make for a much smaller disk footprint (with consequent I/O
savings) and would solve problems like the one you have. Unfortunately
the backward-compatibility issues seem a bit daunting :-(. It's
probably not completely impossible, but how do we preserve the existing
behavior that you can "SELECT * FROM seqname" and get the parameters?

Ideally I'd like
SELECT * FROM seqname; -- gets params of one sequence
SELECT * FROM pg_sequence; -- gets params of all sequences

One possible kluge is to make all the sequences be child tables of a
pg_sequence catalog that exists only to be their inheritance parent.
This seems pretty ugly from a performance point of view though.
Selecting from pg_sequence would be really expensive if you have a lot
of sequences, and there wouldn't be any opportunity for reducing the
disk footprint.

(Thinks a bit...) Maybe it would work for pg_sequence to be a real
catalog with a row per sequence, and we also create a view named after
the sequence that simply selects from pg_sequence with an appropriate
WHERE condition.

Plan C would be to say that we don't need to preserve "SELECT * FROM
seqname", but I'll bet there would be some hollering.

regards, tom lane