Re: Transaction Snapshots and Hot Standby

Simon Riggs <simon@2ndQuadrant.com> writes:

> So passing xl_xmin from master to standby seems not necessary to me. The
> standby's OldestXmin needs to be passed through to the master, not the
> other way around so that WAL records for tuple removal are not
> generated.

I think most people were pretty leery of doing it that way because it means
activity on the standby database can cause the master to bloat. The consensus
seemed to be headed towards having WAL replay on the standby stall if it meets
a tuple removal record for a tuple that's visible to a query running on it.
Probably with a mechanism to configure a maximum amount of time it can be
stalled before shooting those queries.

--  Gregory Stark EnterpriseDB          http://www.enterprisedb.com Ask me about EnterpriseDB's RemoteDBA services!