| From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Deriving Recovery Snapshots |
| Date: | 2008-10-22 17:42:03 |
| Message-ID: | 48FF65EB.4080205@enterprisedb.com |
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| Lists: | pgsql-hackers |
Simon Riggs wrote:
> On Wed, 2008-10-22 at 17:18 +0300, Heikki Linnakangas wrote:
>
>> It doesn't need to be in subtrans before it appears on
>> disk, AFAICS.
>
> I don't make these rules. Read comments in AssignTransactionId().
You mean this one:
> /*
> * Generate a new Xid and record it in PG_PROC and pg_subtrans.
> *
> * NB: we must make the subtrans entry BEFORE the Xid appears anywhere in
> * shared storage other than PG_PROC; because if there's no room for it in
> * PG_PROC, the subtrans entry is needed to ensure that other backends see
> * the Xid as "running". See GetNewTransactionId.
> */
? The way I read that is that as long as there's an entry in
UnobservedXids, we don't need a subtrans entry.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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