> Vadim, can you remind me what UNDO is used for?
Ok, last reminder -:))
On transaction abort, read WAL records and undo (rollback)
changes made in storage. Would allow:
1. Reclaim space allocated by aborted transactions.
2. Implement SAVEPOINTs.
Just to remind -:) - in the event of error discovered by server
- duplicate key, deadlock, command mistyping, etc, - transaction
will be rolled back to the nearest implicit savepoint setted
just before query execution; - or transaction can be aborted by
ROLLBACK TO <savepoint_name> command to some explicit savepoint
setted by user. Transaction rolled back to savepoint may be continued.
3. Reuse transaction IDs on postmaster restart.
4. Split pg_log into small files with ability to remove old ones (which
do not hold statuses for any running transactions).
Vadim
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