On Wed, 2021-09-29 at 11:26 +0200, Peter J. Holzer wrote:
> I discovered this technique back in my Oracle days but it dropped out of
> my toolbox when I switched to PostgreSQL. Recently I had reason to
> revisit it, so I thought I should share it (trivial though it is).
>
> So the solution is to use a single sequence for all the id columns.
>
> Possible drawbacks:
>
> * The ids will grow faster, and they will be large even on small
> tables. It may be a bit irritating if you have a table with just 5
> rows and the ids are 5, 6, 7, 12654, 345953.
That's why use use "bigint".
> * Bottleneck? Using a single sequence was said to be a performance
> bottleneck in Oracle. I didn't notice a performance difference then
> and I doubt it would be one in PostgreSQL, but if in doubt, measure!
That's no problem if you define the sequence with a CACHE value
above 1, so that not every "nextval" call hits the sequence.
> * Doesn't work with IDENTIY - those columns always use implicit
> sequences.
Right.
> * currval() is pretty useless with a global sequence. But I basically
> never use that anyway.
Same here.
I think identity columns are a Good Thing, particularly when CREATED ALWAYS,
and I don't see the advantage of a database-wide unique identifier.
But if it gives you a warm fuzzy feeling, go fot it :^)
Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com
