Re: vacuum on table with all rows frozen

On 04/01/2017 09:09 AM, Tom DalPozzo wrote:
> Hi,
> let's suppose I have a table which after beign populated with only
> INSERTs, doesn't receive no more writing queries (neither insert or
> update or delete). Only reading queries.
> Once all table rows get frozen by (auto)vacuum, will a next (auto)vacuum
> scan that table for any reason or does it understand that it would be
> useless (as no more rows to mark as forzen and no dead tuples) ?

What version of Postgres?

Don't vacuum all-frozen pages.:

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=fd31cd265138019dcccc9b5fe53043670898bc9f

That made it into 9.6:
https://www.postgresql.org/docs/9.6/static/release-9-6.html

E.3.3.1.6. VACUUM

Avoid re-vacuuming pages containing only frozen tuples (Masahiko Sawada,
Robert Haas, Andres Freund)

> As I will have hunderds of big tables like that, I want to be sure that
> the vacuum process doesn't waste time.
> Regards
> Pupillo
>
>
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com