| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Bruce Momjian <bruce(at)momjian(dot)us> |
| Cc: | Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Bug in autovacuum.c? |
| Date: | 2011-03-31 18:59:38 |
| Message-ID: | 201103311859.p2VIxcU09117@momjian.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Bruce Momjian wrote:
> > Yeah, I think this change would have the effect of moving the freeze
> > limit by one (or two?) counts. Given the moving nature of values
> > returned by ReadNewTransactionId this would probably have no practical
> > effect. Still, the code as is seems more natural to me (Tom wrote this
> > bit IIRC, not me).
>
> I am now thinking the code is correct --- it maps values from 0 to
> FirstNormalTransactionId into the top of the (unsigned) xid range.
> Unless someone objects, I will add a C comment about this behavior so
> future readers are not confused.
OK, now I think it is wrong. :-)
The effect is to map max xid + 1 to max xid -
FirstNormalTransactionId(3) + 1, which makes the xid look like it is
going backwards, less than max xid --- not good.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
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