| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Vacuum, Freeze and Analyze: the big picture |
| Date: | 2013-06-03 18:56:35 |
| Message-ID: | 51ACE6E3.4000309@agliodbs.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On 06/03/2013 11:12 AM, Andres Freund wrote:
> On 2013-06-03 11:00:38 -0700, Josh Berkus wrote:
>>
>>>> Also, locking while it does its work.
>>>
>>> Eh?
>>
>> Even if we're doing lazy vacuum, we have to lock a few pages at a time
>> of each table. This does result in response time delays on the current
>> workload, which can be quite bad if it's a highly contended table already.
>
> We don't really lock more pages at a time than normal DML does. 1 heap
> page at a time, possibly several index pages at once.
Really? I though vacuum held onto its locks until it reached
vacuum_cost. If it doesn't, then maybe we should adjust the default for
vacuum_cost_limit upwards.
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com
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