Re: Idea for nested transactions / savepoints

Bruce Momjian <pgman@candle.pha.pa.us> writes:
>> The complaints about WAL size amount to "we don't have the disk space
>> to keep track of this, for long-running transactions".  If it doesn't
>> fit on disk, how likely is it that it will fit in memory?

> Sure, we can put on the disk if that is better.

I think you missed my point.  Unless something can be done to make the
log info a lot smaller than it is now, keeping it all around until
transaction end is just not pleasant.  Waving your hands and saying
that we'll keep it in a different place doesn't affect the fundamental
problem: if the transaction runs a long time, the log is too darn big.

There probably are things we can do --- for example, I bet an UNDO
log kept in this way wouldn't need to include page images.  But it's
that sort of consideration that will make or break UNDO, not where
we store the info.
        regards, tom lane