Re: Heavily modified big table bloat even in auto vacuum is running

On 12 November 2013 08:47 Amit Kapila wrote:
> On Mon, Nov 11, 2013 at 3:14 PM, Haribabu kommi
> <haribabu(dot)kommi(at)huawei(dot)com> wrote:
> > On 08 November 2013 18:35 Amit Kapila wrote:
> >> On Fri, Nov 8, 2013 at 10:56 AM, Haribabu kommi
> >> <haribabu(dot)kommi(at)huawei(dot)com> wrote:
> >> > On 07 November 2013 09:42 Amit Kapila wrote:
> >> > 1. Taking a copy of n_dead_tuples before VACUUM starts and then
> >> subtract it once it is done.
> >> > This approach doesn't include the tuples which are remains
> >> > during
> >> the vacuum operation.

Patch is modified as take a copy of n_dead_tuples during vacuum start and use
the same while calculating the new dead tuples at end of vacuum.

> >> By the way, do you have test case or can you try to write a test
> case
> >> which can show this problem and then after fix, you can verify if
> the
> >> problem is resolved.
> >
> > The simulated index bloat problem can be generated using the attached
> script and sql.
> > With the fix of setting the dead tuples properly,
>
> Which fix here you are referring to, is it the one which you have
> proposed with your initial mail?
>
> > the bloat is reduced and by changing the vacuum cost Parameters the
> > bloat is avoided.

With the simulated bloat test run for 1 hour the bloat occurred as below,

Unpatched - 1532MB
Patched - 1474MB

With this patched approach the bloat is reduced.

Regards,
Hari babu.