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Re: detection of VACUUM in progress

From: Ben-Nes Yonatan <da(at)canaan(dot)co(dot)il>
To: Bohdan Linda <bohdan(dot)linda(at)seznam(dot)cz>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: detection of VACUUM in progress
Date: 2005-08-31 16:16:35
Message-ID: 4315D7E3.2070201@canaan.co.il (view raw or flat)
Thread:
Lists: pgsql-general
Bohdan Linda wrote:
>>From the postgresql manual 
>>http://www.postgresql.org/docs/8.0/interactive/maintenance.html :
>>" The standard form of VACUUM is best used with the goal of maintaining 
>>a fairly level steady-state usage of disk space. If you need to return 
>>disk space to the operating system you can use VACUUM FULL ? but what's 
>>the point of releasing disk space that will only have to be allocated 
>>again soon? Moderately frequent standard VACUUM runs are a better 
>>approach than infrequent VACUUM FULL runs for maintaining 
>>heavily-updated tables."
>>
>>From this I conclude that an ordinary VACUUM is sufficent to your 
>>purpose cause you insert/delete almost the same amount of data daily.
>>
>>But then again I can be mistaken so if anyone can back me up here or 
>>throw the manual on me will be nice ;P
> 
> 
> 
> If I vacuum only the table, the records may be used by new lines, that is
> fine. Problem is, that when creating select on such table, it takes more
> pages to be read from the IO (it will read laso deleted rows) thus the
> select will last a bit longer. 
> 
> regards,
> Bohdan 
> 

As far as I understand the vacuum process, it does delete the "deleted 
rows" so the next queries after the vacuum will not read those rows.
Of course that the table will be the same size as with the "deleted 
rows" but I dont think that with a proper index it will result in any 
meaningful overhead...

But then again its just my opinion and anyway lately im feeling 
increasingly amateur at this subject... :)

Cheers!
Ben-Nes Yonatan

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