| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: pg_sequence catalog |
| Date: | 2016-08-31 18:30:02 |
| Message-ID: | 20160831183002.acmwkaovaigm4tjb@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
On 2016-08-31 14:23:41 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2016-08-31 13:59:48 -0400, Tom Lane wrote:
> >> You are ignoring the performance costs associated with eating 100x more
> >> shared buffer space than necessary.
>
> > I doubt that's measurable in any real-world scenario. You seldomly have
> > hundreds of thousands of sequences that you all select from at a high
> > rate.
>
> If there are only a few sequences in the database, cross-sequence
> contention is not going to be a big issue anyway.
Isn't that *precisely* when it's going to matter? If you have 5 active
tables & sequences where the latter previously used independent locks,
and they'd now be contending on a single lock. If you have hundreds of
thousands of active sequences, I doubt individual page locks would
become a point of contention.
Andres
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