Re: Autovacuum fails to keep visibility map up-to-date in mostly-insert-only-tables

On Thu, Oct  9, 2014 at 02:34:17PM +0400, Alexey Bashtanov wrote:
> Hello!
> 
> Autovacuum daemon performs vacuum when the number of rows
> updated/deleted (n_dead_tuples) reaches some threshold.
> Similarly it performs analyze when the number of rows changed in any
> way (incl. inserted).
> When a table is mostly insert-only, its visibility map is not
> updated as vacuum threshold is almost never reached, but analyze
> does not update visibility map.
> 
> Why could it be a bad idea to run vacuum after some number of any
> changes including inserts, like analyze?
> Or at least make it tunable by user (add a second bunch of paramters
> to control second vacuum threshold, disabled by default)?

I agree this is a serious problem.  We have discussed various options,
but have not decided on anything.  The TODO list has:
https://wiki.postgresql.org/wiki/Todo
Improve setting of visibility map bits for read-only and insert-onlyworkloads
http://www.postgresql.org/message-id/20130906001437.GA29264@momjian.us


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http://enterprisedb.com
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