Re: Savepoints

> > There is no reason for other backend to be able to see savepoint undo
> > information, and keeping it private greatly simplifies the
> > implementation.
> 
> Yes... and requires additional memory/disk space: we keep old records
> in data files and we'll store them again...
> 
> How about: use overwriting smgr + put old records into rollback
> segments - RS - (you have to keep them somewhere till TX's running
> anyway) + use WAL only as REDO log (RS will be used to rollback TX'
> changes and WAL will be used for RS/data files recovery).
> Something like what Oracle does.

I am sorry.  I see what you are saying now.  I missed the words
"overwriting smgr".  You are suggesting going to an overwriting storage
manager.  Is this to be done only because of savepoints.  Doesn't seem
worth it when I have a possible solution without such a drastic change.
Also, overwriting storage manager will require MVCC to read through
there to get accurate MVCC visibility, right?

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026