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? :-) -- Simon Riggs 2ndQuadrant http://www.2ndQuadrant.com ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
