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Re: [Bizgres-general] WAL bypass for INSERT, UPDATE and

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [Bizgres-general] WAL bypass for INSERT, UPDATE and
Date: 2005-12-24 04:06:21
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Greg Stark <gsstark(at)mit(dot)edu> writes:
> It seems to me the only rational way to approach this is to have a per-table
> flag that sets that table to be non-logged. Essentially changing a table's
> behaviour to that of a temporary table except that other transactions can see
> it.

But what's the point?  Nowhere in your scenario is there a reason why
we need to have multiple sessions working on the data being loaded.
So a temp table solves the problem perfectly.  (Temp tables do span
transactions, just not sessions.)

I've got a fundamental philosophical objection to proposals in this
line, which I suppose I'd better state for the record.  I don't like
inventing nonstandard SQL extensions or peculiar semantics just to gain
performance.  It imposes extra complexity on users that they could do
without; the first time someone loses critical data because he didn't
fully understand the tradeoffs involved, he'll have a justifiable gripe.
I also don't like playing Oracle's or MySQL's game by inventing
proprietary syntax.  We claim to believe in standards compliance, so we
should have a pretty high bar for inventing nonstandard syntax.  When
the proposed change has a narrow use-case and is only going to yield
marginal improvements even in that case, I think we should just say no.

Bottom line: if we can't figure out how to do it transparently, I think
we haven't thought hard enough.

			regards, tom lane

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