Re: Deriving Recovery Snapshots

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