What happens when a vacuum full is canceled? Is any of the completed
work retained, or is everything lost?



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The general principle is that any transaction that is being canceled
is fully lost and the database remains in the same state as before
the transaction was started.

I don't know the pgsql internals but I don't see why this shouldn't
be the case for a VACUUM too.

Marc

At 1:23 PM -0400 4/21/04, Michael Guerin wrote:

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Sure, however this is not a data consistency issue, it's a maintenance
routine. If its shuffling around data to free up pages, it seems it
should be able to save some of this work. For instance, SQL server has
a command to defrag an index: dbcc indexdefrag which I believe is
similar to vacuum, in that it reorganizes the data check out:.
http://msdn.microsoft.com/library/de..._dbcc_30o9.asp


M. Bastin wrote:


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Michael Guerin <guerin (AT) rentec (DOT) com> writes:
You lose it all; in fact you are worse off than when you started,
because there is now *more* work for the next vacuum to do --- it
has to clean up the dead tuples that the canceled vacuum created
(in the process of moving data around) and never got to commit.

However, this is on a per-table basis --- if you are running a
database-wide vacuum full, it commits after each table, so the
already-processed tables are done.

regards, tom lane

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