| From: | "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> |
|---|---|
| To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Robert Treat" <xzilla(at)users(dot)sourceforge(dot)net> |
| Cc: | "Decibel!" <decibel(at)decibel(dot)org>, "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>, "Bruce Momjian" <bruce(at)momjian(dot)us>, <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: XID wraparound and busy databases |
| Date: | 2007-08-15 22:58:19 |
| Message-ID: | 46C33EBA.EE98.0025.0@wicourts.gov |
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| Lists: | pgsql-hackers |
>>> On Wed, Aug 15, 2007 at 5:06 PM, in message <7968(dot)1187215570(at)sss(dot)pgh(dot)pa(dot)us>,
Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Treat <xzilla(at)users(dot)sourceforge(dot)net> writes:
>> I'm a little confused, wouldnt the transaction that waits 30 minutes before
>> modifying data need to get an XID that jives with the system when it's
>> transaction started, not when it began manipulating data?
>
> Why?
>
>> Would it really be safe to take a new snapshot at that time,
>
> You wouldn't take a new snapshot. The thought that occurs to me is that
> there's no reason that a transaction has to have an XID for itself
> before it takes a snapshot. We always special-case our own XID anyway.
I'm having trouble picturing how that would work with a transaction using
the SERIALIZABLE transaction isolation level, or would this just be done at
the READ COMMITTED level?
-Kevin
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