On Thu, Aug 22, 2019 at 1:34 AM Dilip Kumar <dilipbal...@gmail.com> wrote: > Yeah, we can handle the bulk fetch as you suggested and it will make > it a lot easier. But, currently while registering the undo request > (especially during the first pass) we need to compute the from_urecptr > and the to_urecptr. And, for computing the from_urecptr, we have the > end location of the transaction because we have the uur_next in the > transaction header and that will tell us the end of our transaction > but we still don't know the undo record pointer of the last record of > the transaction. As of know, we read previous 2 bytes from the end of > the transaction to know the length of the last record and from there > we can compute the undo record pointer of the last record and that is > our from_urecptr.=
I don't understand this. If we're registering an undo request at "do" time, we don't need to compute the starting location; we can just remember the UndoRecPtr of the first record we inserted. If we're reregistering an undo request after a restart, we can (and, I think, should) work forward from the discard location rather than backward from the insert location. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
