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

On 12/29/18, Mithun Cy <mithun(dot)cy(at)enterprisedb(dot)com> wrote:
> Results are execution time(unit ms) taken by copy statement when number of
> records equal to exact number which fit HEAP_FSM_CREATION_THRESHOLD = 4
> pages. For fill factor 20 it is till tid (3, 43) and for scale factor 70
> till tid (3, 157). Result is taken as a median of 10 runs.

> So 2-3% consistent regression, And on every run I can see for patch v11
> execution time is slightly more than base.

Thanks for testing!

> I also tried to insert more
> records till 8 pages and same regression is observed! So I guess even
> HEAP_FSM_CREATION_THRESHOLD = 4 is not perfect!

That's curious, because once the table exceeds the threshold, it would
be allowed to update the FSM, and in the process write 3 pages that it
didn't have to in the 4 page test. The master branch has the FSM
already, so I would expect the 8 page case to regress more.

What I can do later is provide a supplementary patch to go on top of
mine that only checks the last block. If that improves performance,
I'll alter my patch to only check every other page.

-John Naylor