Re: visibility map and reltuples - Mailing list pgsql-hackers

From Heikki Linnakangas
Subject Re: visibility map and reltuples
Date
Msg-id 49465A7A.2070103@enterprisedb.com
Whole thread Raw
In response to Re: visibility map and reltuples  (Greg Stark <greg.stark@enterprisedb.com>)
Responses Re: visibility map and reltuples  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
Greg Stark wrote:
> I wonder if we should switch to keeping reltuplesperpage instead. Then a 
> partial vacuum could update it by taking the average number of tuples 
> per page forbthe pages it saw. Perhaps adjusting it to the weights 
> average between the old value and the new value based on how many pages 
> were seen.

The pages scanned by a partial vacuum isn't a random sample of pages in 
the table. That would bias the reltuplesperpage value towards those 
pages that are updated more.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com


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