Re: How long - Vacumm full - 10 million to 90,000

From: Steve Crawford <scrawford(at)pinpointresearch(dot)com>
To: emilu(at)encs(dot)concordia(dot)ca
Cc: PostgreSQL-SQL <pgsql-sql(at)postgresql(dot)org>
Subject: Re: How long - Vacumm full - 10 million to 90,000
Date: 2008-05-29 16:44:11
Message-ID: 483EDD5B.3030608@pinpointresearch.com
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Emi Lu wrote:
> ...
> I have a table from around 10 million to 90,000, after deletion, I
> tried to use vacuum full, but it seems that it takes forever to
> finish. Could anyone tell me how long it will take to finish the
> Recovering disk space please?
No. Probably a looooonnnnnng time.

In a case like this where you are retaining less than 1% of your records
you are likely to see far, far faster results using CLUSTER - with the
added advantage that CLUSTER will create fresh indexes for you, too.

Alternately, you can:
CREATE TABLE xxx as SELECT * from yourtable;
TRUNCATE yourtable;
INSERT into yourtable SELECT * from xxx;
DROP TABLE xxx;

If you are so close to out-of-space on your disk that you don't have the
room those 90,000 records will require, you may have to dump/restore
using another machine.

Cheers,
Steve

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