Обсуждение: auto-vacuum vs. full table update

An update to our system means I'm going to be rewriting every row of
some large tables (20 million rows by 15 columns).  In a situation
like this, can auto-vacuum take care of it, or should I plan on
vacuum-full/reindex to clean up?

This is 8.4.4.

Thanks,
Craig

On 04/26/2012 12:49 PM, Craig James wrote:
>
> An update to our system means I'm going to be rewriting every row of
> some large tables (20 million rows by 15 columns).  In a situation
> like this, can auto-vacuum take care of it, or should I plan on
> vacuum-full/reindex to clean up?
>

If you rewrite the whole table, you will end up with a table twice the
size, it will not be compacted but as the table grows, the old space
will be reused.

jD

> This is 8.4.4.
>
> Thanks,
> Craig
>


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On 04/26/2012 12:49 PM, Craig James wrote:
> An update to our system means I'm going to be rewriting every row of
> some large tables (20 million rows by 15 columns).  In a situation
> like this, can auto-vacuum take care of it, or should I plan on
> vacuum-full/reindex to clean up?
>
If you want to reclaim the space, a vacuum-full/reindex will do it. But
you are probably better off using cluster. Way faster and you get new
indexes as a by-product. Both methods require an exclusive lock on the
table. If you can't afford the downtime, check out pg_reorg
(http://pgfoundry.org/projects/reorg/)

Cheers,
Steve

Craig James <cjames@emolecules.com> wrote:
> An update to our system means I'm going to be rewriting every row
> of some large tables (20 million rows by 15 columns).  In a
> situation like this, can auto-vacuum take care of it, or should I
> plan on vacuum-full/reindex to clean up?
>
> This is 8.4.4.

If there is any way for you to update in "chunks", with a vacuum
after each chunk, that will prevent the extreme bloat.

-Kevin