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Re: AW: AW: Re: Backup and Recovery

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Zeugswetter Andreas SB <ZeugswetterA(at)wien(dot)spardat(dot)at>
Cc: Vadim Mikheev <vmikheev(at)sectorbase(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: AW: AW: Re: Backup and Recovery
Date: 2001-07-06 14:20:48
Message-ID: 9920.994429248@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Zeugswetter Andreas SB <ZeugswetterA(at)wien(dot)spardat(dot)at> writes:
>> Wouldn't it be the same as the case where we *do* have UNDO?  How is a
>> removed tuple different from a tuple that was never there?

> HiHi, the problem is a subtile one. What if a previously aborted txn 
> produced a btree page split, that would otherwise not have happened ?

Good point.  We'd have to recognize btree splits (and possibly some
other operations) as things that must be done anyway, even if their
originating transaction is aborted.

There already is a mechanism for doing that: xlog entries can be written
without any transaction identifier (see XLOG_NO_TRAN).  Seems to me that
btree split XLOG records should be getting written that way now --- Vadim,
don't you agree?

			regards, tom lane

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