Added to TODO: * Allow one transaction to see tuples using the snapshot of another transaction
This would assist multiple backends in working together. http://archives.postgresql.org/pgsql-hackers/2008-01/msg00400.php --------------------------------------------------------------------------- Chris Browne wrote: > [EMAIL PROTECTED] (Simon Riggs) writes: > > On Fri, 2008-01-11 at 20:39 +0000, Simon Riggs wrote: > >> On Fri, 2008-01-11 at 15:05 -0500, Tom Lane wrote: > >> Simon Riggs <[EMAIL PROTECTED]> writes: > >> > > If we had a function > >> > > replace_serializable_snapshot(master_xid, txid_snapshot) > >> > > this would allow us to use the txid_snapshot values to replace our > >> > > transaction's serializable snapshot. > >> > > >> > ... whereupon we'd get wrong answers. Certainly you could not allow > >> > transaction xmin to go backwards, and I'm not sure what other > >> > restrictions there would be, but the whole thing gives me the willies. > > > > Sorry, forgot to add > > - global xmin isn't going backwards > > - neither is latest completed xid > > > > The xmin of the transaction will go backwards, but as long as we don't > > do anything prior to the setting of the cloned snapshot, what can go > > wrong? :-) > > Note that we required that the "provider transaction" have the > attributes IsXactIsoLevelSerializable and XactReadOnly both being > true, so we have the mandates that the resultant backend process: > > a) Is in read only mode, and > b) Is in serializable mode. > > That's a pair of (possibly stretching-wide!) suspenders worth of > support from Evil... > -- > (format nil "[EMAIL PROTECTED]" "cbbrowne" "cbbrowne.com") > http://linuxfinances.info/info/internet.html > Trying to be happy is like trying to build a machine for which the > only specification is that it should run noiselessly. > > ---------------------------(end of broadcast)--------------------------- > TIP 6: explain analyze is your friend -- Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us EnterpriseDB http://enterprisedb.com + If your life is a hard drive, Christ can be your backup. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
