Re: Unhappy about API changes in the no-fsm-for-small-rels patch

On Thu, Apr 18, 2019 at 2:10 PM John Naylor <john(dot)naylor(at)2ndquadrant(dot)com> wrote:
>
> On Thu, Apr 18, 2019 at 2:48 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > I respect and will follow whatever will be the consensus after
> > discussion. However, I request you to wait for some time to let the
> > discussion conclude. If we can't get to an
> > agreement or one of John or me can't implement what is decided, then
> > we can anyway revert it.
>
> Agreed. I suspect the most realistic way to address most of the
> objections in a short amount of time would be to:
>
> 1. rip out the local map
> 2. restore hio.c to only checking the last block in the relation if
> there is no FSM (and lower the threshold to reduce wasted space)
> 3. reduce calls to smgr_exists()
>

Won't you need an extra call to RelationGetNumberofBlocks to find the
last block? Also won't it be less efficient in terms of dealing with
bloat as compare to current patch? I think if we go this route, then
we might need to revisit it in the future to optimize it, but maybe
that is the best alternative as of now.

I am thinking that we should at least give it a try to move the map to
rel cache level to see how easy or difficult it is and also let's wait
for a day or two to see if Andres/Tom has to say anything about this
or on the response by me above to improve the current patch.

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