| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Jim Nasby <jim(at)nasby(dot)net> |
| Cc: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Why is autovacuum_freeze_max_age a postmaster setting? |
| Date: | 2014-03-21 21:55:45 |
| Message-ID: | 20140321215545.GE17111@alap3.anarazel.de |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Hi,
On 2014-03-21 16:49:53 -0500, Jim Nasby wrote:
> Why do we require a restart to change autovacuum_freeze_max_age? Can’t
> we respawn the autovac workers to pick up the setting? (Or just pass
> the HUP down to them?)
It's more complex than notifying the workers. There's limits in shared
memory that's computed based on it. Check
varsup.c:SetTransactionIdLimit(). It's not entirely trivial to trigger
recomputation of that value via the GUC machinery in a sensible way...
But yes, I'd wished it were PGC_SIGHUP before as well.
I guess we could delegate responsibility of updating the shared memory
value to the autovac launcher?
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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