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Re: AW: AW: AW: AW: WAL-based allocation of XIDs is insecur e

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Zeugswetter Andreas SB <ZeugswetterA(at)wien(dot)spardat(dot)at>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: AW: AW: AW: AW: WAL-based allocation of XIDs is insecur e
Date: 2001-03-06 18:18:53
Message-ID: 6595.983902733@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Zeugswetter Andreas SB  <ZeugswetterA(at)wien(dot)spardat(dot)at> writes:
> I do not however see how the current solution fixes the original problem,
> that we don't have a rollback for index modifications.
> The index would potentially point to an empty heaptuple slot.

How?  There will be an XLOG entry inserting the heap tuple before the
XLOG entry that updates the index.  Rollforward will redo both.  The
heap tuple might not get committed, but it'll be there.

> Additionally I do not see how this all works for userland index types.

None of it works for index types that don't do XLOG entries (which I
think may currently be true for everything except btree :-( ...).  I
don't see how that changes if we alter the way this bit is done.

			regards, tom lane

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