| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Noah Misch <noah(at)leadboat(dot)com> |
| Subject: | Re: New IndexAM API controlling index vacuum strategies |
| Date: | 2021-03-23 03:33:55 |
| Message-ID: | CAH2-Wz=W_70JdwmgJZ7KoaY1rP=HV2NiobGJPweUbXQOrmkTbg@mail.gmail.com |
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On Mon, Mar 22, 2021 at 8:28 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> You seem to be concerned about a similar contradiction. In fact it's
> *very* similar contradiction, because this new GUC is naturally a
> "sibling GUC" of both vacuum_freeze_table_age and
> autovacuum_vacuum_max_age (the "units" are the same, though the
> behavior that each GUC triggers is different -- but
> vacuum_freeze_table_age and autovacuum_vacuum_max_age are both already
> *similar and different* in the same way). So perhaps the solution
> should be similar -- silently interpret the setting of the new GUC to
> resolve the contradiction.
More concretely, maybe the new GUC is forced to be 1.05 of
vacuum_freeze_table_age. Of course that scheme is a bit arbitrary --
but so is the existing 0.95 scheme.
There may be some value in picking a scheme that "advertises" that all
three GUCs are symmetrical, or at least related -- all three divide up
the table's XID space.
--
Peter Geoghegan
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