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

From: Andres Freund <andres(at)anarazel(dot)de>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, John Naylor <john(dot)naylor(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Unhappy about API changes in the no-fsm-for-small-rels patch
Date: 2019-04-18 21:10:29
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On 2019-04-17 12:20:29 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2019-04-17 15:49:29 +0530, Amit Kapila wrote:
> >> OTOH, if we want to extend it later for whatever reason to a relation
> >> level cache, it shouldn't be that difficult as the implementation is
> >> mostly contained in freespace.c (fsm* functions) and I think the
> >> relation is accessible in most places. We might need to rip out some
> >> calls to clearlocalmap.
> > But it really isn't contained to freespace.c. That's my primary
> > concern. You added new parameters (undocumented ones!),
> > FSMClearLocalMap() needs to be called by callers and xlog, etc.
> Given where we are in the release cycle, and the major architectural
> concerns that have been raised about this patch, should we just
> revert it and try again in v13, rather than trying to fix it under
> time pressure? It's not like there's not anything else on our
> plates to fix before beta.

Hm. I'm of split mind here:

It's a nice improvement, and the fixes probably wouldn't be that
hard. And we could have piped up a bit earlier about these concerns (I
only noticed this when rebasing zheap onto the newest version of

But as you it's also late, and there's other stuff to do. Although I
think neither Amit nor John is heavily involved in any...

My compromise suggestion would be to try to give John and Amit ~2 weeks
to come up with a cleanup proposal, and then decide whether to 1) revert
2) apply the new patch, 3) decide to live with the warts for 12, and
apply the patch in 13. As we would already have a patch, 3) seems like
it'd be more tenable than without.



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