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(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026