Re: WIP: Avoid creation of the free space map for small tables

On Wed, Jan 30, 2019 at 10:41 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> On Wed, Jan 30, 2019 at 4:33 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Tue, Jan 29, 2019 at 8:12 PM John Naylor <john(dot)naylor(at)2ndquadrant(dot)com> wrote:
> > >
> > > On Tue, Jan 29, 2019 at 11:56 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > >
> > > > You can find this change in attached patch. Then, I ran the make
> > > > check in src/bin/pgbench multiple times using test_conc_insert.sh.
> > > > You can vary the number of times the test should run, if you are not
> > > > able to reproduce it with this.
> > > >
> > > > The attached patch (clear_local_map_if_exists_1.patch) atop the main
> > > > patch fixes the issue for me. Kindly verify the same.
> > >
> > > I got one failure in 50 runs. With the new patch, I didn't get any
> > > failures in 300 runs.
> > >
> >
> > Thanks for verification. I have included it in the attached patch and
> > I have also modified the page.sql test to have enough number of pages
> > in relation so that FSM will get created irrespective of alignment
> > boundaries. Masahiko San, can you verify if this now works for you?
> >
>
> Thank you for updating the patch!
>
> The modified page.sql test could fail if the block size is more than
> 8kB?

That's right, but I don't think current regression tests will work for
block size greater than 8KB. I have tried with 16 and 32 as block
size, there were few failures on the head itself.

> We can ensure the number of pages are more than 4 by checking it
> and adding more data if no enough but I'm really not sure we should
> care the bigger-block size cases.
>

Yeah, I am not sure either. I think as this is an existing test, we
should not try to change it too much. However, if both you and John
feel it is better to change, we can go with that.

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