Re: Disk space consumed by pk not returned after vacuum or reindex - Mailing list pgsql-admin

I didn't see you mention what version you're running; index bloat
shouldn't be a big issue in 7.4 and above. You also didn't mention
how often you're vacuuming the table. If you don't vacuum the table
frequently enough, you're going to get bloat, plain and simple.

On Oct 5, 2006, at 11:24 AM, Kevin Johnson wrote:
> Thank you for the suggestion, Bruno.  The clustering did the trick
> in reducing the current disk usage, however eventually the disk
> space get consumed once more.  I fear that we may just need to
> update the version of Postgres to help alleviate index bloat!
>
> Bruno Wolff III wrote:
>> On Wed, Sep 13, 2006 at 09:53:16 -0400, Kevin Johnson
>> <Kevin.Johnson@noaa.gov> wrote:
>>> We have a database, which consistently consumes more and more of
>>> the disk space in it's lvol until it reaches 100%. So far, we
>>> have tried to run a full vacuum on the database, with limited
>>> success. Eventually, we had to drop and reload the database with
>>> the same data inside. It brought the disk usage down to 73%. It
>>> then began to creep once more toward 100%. After some research, I
>>> was able to use the pg_class catalog to find that the items which
>>> are expanding the quickest are  primary key (btree) indexes. I
>>> attempted to run a REINDEX on one of the tables with the pk
>>> taking up the largest amount of space. The usage according to
>>> pg_class dropped dramatically, however the disk space was not
>>> returned to the system. So I attempted another full vacuum
>>> afterwards, and still nothing was returned to the system. These
>>> tables are updated extremely frequently (although their total
>>> number of rows is close to constant), which is my guess as to why
>>> the pk indexes increase so rapidly in terms of their disk usage.
>>> Unfortunately, PostgreSQL knowledge is limited, and I was
>>> wondering if anyone had experienced something similar / knows
>>> what else we can do to return this disk space back to the system?
>> This is possibly index bloat due to new keys always being larger
>> than existing keys. This was fixed in later releases. There is
>> still some potential for bloat due to fragmentation, but I believe
>> that has a constant bound. You might try using the cluster
>> command. I think that will both clean up the indexes and remove
>> dead rows and do it faster than using a vacuum full and
>> reindexing. The downside is that the table will be unavailable
>> during the cluster which might be a deal breaker for you.
--
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)


--
Jim Nasby                                    jimn@enterprisedb.com
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)