On 13.02.2013 15:31, Alexander Korotkov wrote:
On Wed, Feb 13, 2013 at 4:51 PM, Greg Stark<st...@mit.edu>  wrote:

Heikki was talking about a generic WAL record type that would just
store a binary delta between the version of the block when it was
locked and when it was unlocked. That would handle any extension
cleanly as far as data modification goes as long as the extension was
working through our buffer manager. It seems like an attractive idea
to me.

It will, for sure, works well when atomic page changes are enough for us.
However, some operations, for example, page splits, contain changes in
multiple pages. Replaying changes in only some of pages is not fair. Now,
it's hard for me to imagine how to generalize it into generic WAL record
type.

You could have a generic WAL record that applies changes to multiple pages atomically.

- Heikki


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