Horton

Re: start of transaction (was: Re: [PERFORM] Help with count(*))

Bruce Momjian <pgman@candle.pha.pa.us>

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From: Bruce Momjian <pgman@candle.pha.pa.us>
To: Hannu Krosing <hannu@tm.ee>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Neil Conway <neilc@samurai.com>, Will LaShell <will@lashell.net>, Christopher Browne <cbbrowne@acm.org>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2003-11-18T00:52:51Z
Lists: pgsql-hackers, pgsql-performance 
Hannu Krosing wrote:
> Bruce Momjian kirjutas E, 17.11.2003 kell 02:31:
> 
> > Defining now() as the first call seems pretty arbitrary to me.  I can't
> > think of any time-based interface that has that API.  And what if a
> > trigger called now() in an earlier query and you didn't even know about
> > it.
> 
> That would be OK. The whole point of that previous discussion was to
> have now() that returns the same value over the span of the whole
> transaction.

I think my issue is that there isn't any predictable way for a user to
know when the now() time is recorded.  By using start of transaction, at
least we know for sure the point in time it is showing.

> It would be even better to have now() that returns the time current
> transaction is COMMITted as this is the time other backend become aware
> of it ;)

True, but implementing that would be very hard.

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