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Re: nested xacts and phantom Xids

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl>,Patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: nested xacts and phantom Xids
Date: 2004-06-20 21:34:41
Message-ID: 10197.1087767281@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> I don't feel too bad about the runtime cost if only subtransactions are
> paying that cost.

That's exactly why I'm so exercised about what's been done to the
HeapTupleSet/Get macros.  That's significant cost that's paid even when
you're not using *any* of this stuff.

> I know we are really stretching the system here but I
> would like to try a little more rather than give up and taking a space
> hit for all tuples.

I don't even have any confidence that there are no fundamental bugs
in the phantom-xid concept :-(.  I'd be willing to play along if an
implementation that seemed acceptable speedwise were being offered,
but this thing is not preferable to four-more-bytes even if it works.

			regards, tom lane

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