From: | Shridhar Daithankar <shridhar_daithankar(at)persistent(dot)co(dot)in> |
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To: | |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Some thoughts about i/o priorities and throttling vacuum |
Date: | 2003-10-17 14:53:35 |
Message-ID: | 3F90026F.3020300@persistent.co.in |
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Lists: | pgsql-hackers |
Matthew T. O'Connor wrote:
> On Fri, 2003-10-17 at 10:25, Shridhar Daithankar wrote:
>
>>OK. So here is what I understand. I have a table which contains 100 rows which
>>appeated there due to some insert operation. Then I vacuum it. And sit there for
>>internity for rest of the database to approach the singularity(the xid
>>wraparound..:-) Nice term, isn't it?).
>>
>>So this static table is vulnerable to xid wraparound? I doubt.
>
>
> No that table would probably be ok, because you did a vacuum on it after
> the inserts. The problem is that pg_autovacuum may choose not to do a
> vacuum if you didn't cross a threshold, or someone outside of
> pg_autovacuum may have done the vacuum and autovac doesn't know about
> it, so it can't guarantee that all tables in the database are safe from
> xid wraparound.
>
> One additional thing, some of this might be possible if pg_autovacuum
> saved its data between restarts. Right now it restarts with no memory
> of what happened before.
Well, the unmaintened gborg version adopted approach of storing such info. in a
table, so that it survives postgresql/pg_atuvacuum restart or both.
That was considered a tablespace pollution back then. But personally I think, it
should be ok. If ever it goes to catalogues, I would rather add few columns to
pg_class for such a stat. But again, thats not my call to make.
Shridhar
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