Re: lazy vacuum blocks analyze

Alvaro Herrera píše v st 06. 05. 2009 v 15:11 -0400:
> Zdenek Kotala wrote:
> 
> > If there is not another problem I suggest to use two different locks for
> > vacuum and analyze.
> 
> By itself that won't work -- see vac_update_relstats.

It says:

*      Note another assumption: that two VACUUMs/ANALYZEs on a table can't
*      run in parallel, nor can VACUUM/ANALYZE run in parallel with a
*      schema alteration such as adding an index, rule, or trigger.  Otherwise
*      our updates of relhasindex etc might overwrite uncommitted updates.

But what "two VACUUMs/ANALYZEs on a table" exactly means? It is not
clear here if VACUUMxANALYZE parallel run is allowed or not. I also
don't see explanation why it is not allowed? From code I don't see any
problem here.
Zdenek