Search Postgresql Archives

Re: Mysteriously varying index scan costs

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Pavan Deolasee wrote:
> On Mon, Sep 24, 2018 at 2:20 PM, Laurenz Albe <laurenz.albe@xxxxxxxxxxx> wrote:
> > 
> > But how can it be that the first run has to touch 74917 blocks,
> > while whe second run only needs to touch 1185?
> > 
> 
> The first index scan may have killed lots of index tuples.

So the first index scan visited lots of table tuples, found them
dead, and set the LP_DEAD flag on the corresponding index items
so that subsequent index scans could ignore them, right?

Thanks, that must be the correct explanation.  It correlates nicely
with the dirtied pages, too.

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com





[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]

  Powered by Linux