Re: Is there a way to make VACUUM run completely outside

On Mon, Feb 07, 2005 at 07:16:41PM +0200, Hannu Krosing wrote:

> If all the changes it does to internal data storage can be rolled back,
> then I can't see how VACUUM FULL can work at all without requiring 2x
> the filesize for the ROLLBACK.

I think the point is that the table is still consistent if the system
crashes while vacuum is running. For the internal details, see Xvac in
the HeapTupleHeader struct.

> Also, why must it be run outside of transaction block if it can be
> rollbacked ?

A vacuum actually uses several transactions, so it wouldn't work as the
user would expect if run in a transaction. The first one is committed
rather early and new ones are opened and closed. (One per table, IIRC.)

--
Alvaro Herrera (<alvherre[(at)]dcc(dot)uchile(dot)cl>)
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