From: | "Mikheev, Vadim" <vmikheev(at)SECTORBASE(dot)COM> |
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To: | "'Bruce Momjian'" <pgman(at)candle(dot)pha(dot)pa(dot)us> |
Cc: | "'Tom Lane'" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
Subject: | RE: Plans for solving the VACUUM problem |
Date: | 2001-05-19 01:10:10 |
Message-ID: | 3705826352029646A3E91C53F7189E3201662E@sectorbase2.sectorbase.com |
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Lists: | pgsql-hackers |
> 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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