Re: Bug in autovacuum.c? - Mailing list pgsql-hackers

From Jim Nasby
Subject Re: Bug in autovacuum.c?
Date
Msg-id D9F4A89E-4EB2-4B4C-B0A4-E9E2144BDC22@nasby.net
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In response to Re: Bug in autovacuum.c?  (Bruce Momjian <bruce@momjian.us>)
List pgsql-hackers
On Apr 1, 2011, at 4:48 PM, Bruce Momjian wrote:
> I am not so concerned about this case but about other cases where we are
> computing xid distances across the invalid range.

Bruce, I think you hit the nail on the head earlier:

> To do the right thing every computation that passes over the xid
> wraparound bounary should subtract FirstNormalTransactionId, not just
> those that fall in the boundry.

Put another way: XID calculations should not use just +/-, but an operator (presumably a macro) that understands
wraparoundand the special values. Surely we have a similar problem in the code that increments XIDs, and possibly other
placesas well. 
--
Jim C. Nasby, Database Architect                   jim@nasby.net
512.569.9461 (cell)                         http://jim.nasby.net




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