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

On Mon, Feb 4, 2019 at 9:24 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Mon, Feb 4, 2019 at 8:47 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> One more similar failure:
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=lapwing&dt=2019-02-04%2003%3A20%3A01
>
> So, basically, this is due to difference in the number of tuples that
> can fit on a page. The freespace in FSM for the page is shown
> different because of available space on a particular page. This can
> vary due to alignment. It seems to me we can't rely on FSM contents
> if there are many tuples in a relation. One idea is to get rid of
> dependency on FSM contents in this test, can you think of any better
> way to have consistent FSM contents across different platforms?
>

One more idea could be that we devise a test (say with a char/varchar)
such that it always consume same space in a page irrespective of its
alignment. Yet another way could be we use explain (costs off,
analyze on, timing off, summary off) ..., this will ensure that we
will have test coverage for function fsm_page_contents, but we don't
rely on its contents. What do you think? I will go with last option
to stablize the buildfarm tests unless anyone thinks otherwise or has
better idea. I willprobably wait for 20 minutes or so to see if
anyone has inputs.

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