Horton

Re: Should we increase the default vacuum_cost_limit?

Julien Rouhaud <rjuju123@gmail.com>

View thread View on postgr.es
From: Julien Rouhaud <rjuju123@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, David Rowley <david.rowley@2ndquadrant.com>, Jeff Janes <jeff.janes@gmail.com>, Jeremy Schneider <schnjere@amazon.com>, Joe Conway <mail@joeconway.com>, Peter Geoghegan <pg@bowt.ie>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2019-03-10T13:18:26Z
Lists: pgsql-hackers 
On Sat, Mar 9, 2019 at 11:14 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> BTW ... I noticed while fooling with this that GUC's out-of-range
> messages can be confusing:
>
> regression=# set vacuum_cost_delay = '1s';
> ERROR:  1000 is outside the valid range for parameter "vacuum_cost_delay" (0 .. 100)
>
> One's immediate reaction to that is "I put in 1, not 1000".  I think
> it'd be much clearer if we included the unit we'd converted to, thus:
>
> ERROR:  1000 ms is outside the valid range for parameter "vacuum_cost_delay" (0 .. 100)
>
> (Notice that this also implicitly tells what units the range limits
> are being quoted in.

I like it!

> A small problem with this idea is that GUC_UNIT_[X]BLOCK variables don't
> really have a natural unit name.  If we follow the lead of pg_settings,
> such errors would look something like
>
> ERROR:  1000 8kB is outside the valid range for ...
>
> I can't think of a better idea, though, and it'd still be clearer than
> what happens now.
>
> Barring objections I'll go make this happen.

No objection here.

Commits

  1. Allow fractional input values for integer GUCs, and improve rounding logic.

  2. Reduce the default value of autovacuum_vacuum_cost_delay to 2ms.

  3. Revert "Increase the default vacuum_cost_limit from 200 to 2000"

  4. Convert [autovacuum_]vacuum_cost_delay into floating-point GUCs.

  5. Include GUC's unit, if it has one, in out-of-range error messages.

  6. Disallow NaN as a value for floating-point GUCs.

  7. Increase the default vacuum_cost_limit from 200 to 2000