Re: Database size

From: Francisco Reyes <lists(at)stringsutils(dot)com>
To: l(dot)rame(at)griensu(dot)com
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Database size
Date: 2010-01-11 18:42:22
Message-ID: cone.1263235342.384926.30109.1000@shelca
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Leonardo M. Ramé writes:

> A customer of mine asked me to periodically delete old, unneeded records
> containing ByteA fields, because he think it will reduce the database
> size on disk. Is this true?.

No.

> For example, in Firebird, the database size
> is not reduced until you do a Backup-Restore of the database.

Not sure about ByteA, but in general... in potgres you need to do that or a
vacuum full.. or copy all the data of the table into a new table and rename.

Having said that.. if you delete old rows and do a vacuum and/or have
autovacuum enabled the space of those old rows can be re-used, slowing down
the growth of the table. So yes, deleting old rows and doing a vacuum is a
good thing.. but no I don't believe it will reduce database size.

I say "don't believe" because I don't recall if byteA was stored in the
table itself or was stored outside using TOAST.. so I am not sure about
how/when space is released for it.

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