| From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Joachim Wieland <joe(at)mcknight(dot)de>, Marko Tiikkaja <marko(dot)tiikkaja(at)2ndquadrant(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: synchronized snapshots |
| Date: | 2011-10-19 16:20:17 |
| Message-ID: | 4E9EF8C1.3020907@enterprisedb.com |
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| Lists: | pgsql-hackers |
On 19.10.2011 19:17, Tom Lane wrote:
> Joachim Wieland<joe(at)mcknight(dot)de> writes:
>> [ synchronized-snapshots patch ]
>
> Looking through this code, it strikes me that SET TRANSACTION SNAPSHOT
> is fundamentally incompatible with SERIALIZABLE READ ONLY DEFERRABLE
> mode. That mode assumes that you should be able to just take a new
> snapshot, repeatedly, until you get one that's "safe". With the patch
> as written, if the supplied snapshot is "unsafe", GetSafeSnapshot()
> will just go into an infinite loop.
>
> AFAICS we should just throw an error if SET TRANSACTION SNAPSHOT is done
> in a transaction with those properties. Has anyone got another
> interpretation? Would it be better to silently ignore the DEFERRABLE
> property?
An error seems appropriate to me.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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