Re: WIP: Avoid creation of the free space map for small tables - Mailing list pgsql-hackers

From Amit Kapila
Subject Re: WIP: Avoid creation of the free space map for small tables
Date
Msg-id CAA4eK1J0k7zfLLuyWfB3Y+PsBYfHXuiV264nvnJkxXAJuqPcMQ@mail.gmail.com
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In response to Re: WIP: Avoid creation of the free space map for small tables  (John Naylor <john.naylor@2ndquadrant.com>)
Responses Re: WIP: Avoid creation of the free space map for small tables  (John Naylor <john.naylor@2ndquadrant.com>)
List pgsql-hackers
On Wed, Jan 30, 2019 at 8:11 PM John Naylor <john.naylor@2ndquadrant.com> wrote:
>
> On Wed, Jan 30, 2019 at 2:11 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > This is much better than the earlier version of test and there is no
> > dependency on the vacuum.  However, I feel still there is some
> > dependency on how the rows will fit in a page and we have seen some
> > related failures due to alignment stuff.  By looking at the test, I
> > can't envision any such problem, but how about if we just write some
> > simple tests where we can check that the FSM won't be created for very
> > small number of records say one or two and then when we increase the
> > records FSM gets created, here if we want, we can even use vacuum to
> > ensure FSM gets created.  Once we are sure that the main patch passes
> > all the buildfarm tests, we can extend the test to something advanced
> > as you are proposing now.  I think that will reduce the chances of
> > failure, what do you think?
>
> That's probably a good idea to limit risk. I just very basic tests
> now, and vacuum before every relation size check to make sure any FSM
> extension (whether desired or not) is invoked. Also, in my last patch
> I forgot to implement explicit checks of the block number instead of
> assuming how many rows will fit on a page. I've used a plpgsql code
> block to do this.
>

-- Extend table with enough blocks to exceed the FSM threshold
 -- FSM is created and extended to 3 blocks

The second comment line seems redundant to me, so I have removed that
and integrated it in the main patch.


With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

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