| From: | Scott Ribe <scott_ribe(at)elevated-dev(dot)com> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | PostgreSQL General <pgsql-general(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: bad JIT decision |
| Date: | 2020-07-24 22:32:01 |
| Message-ID: | 559519F3-5285-4F2B-A88F-0067382761A7@elevated-dev.com |
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| Thread: | |
| Lists: | pgsql-general |
> On Jul 24, 2020, at 4:26 PM, David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
>
> It does not really take into account the cost of jitting.
That is what I was missing.
I read about JIT when 12 was pre-release; in re-reading after my post I see that it does not attempt to estimate JIT cost. And in thinking about it, I realize that would be next to impossible to anticipate how expensive LLVM optimizstion was going to be.
In the case where a set of functions is replicated across partitions, it would be possible to do them once, then project the cost of the copies. Perhaps for PG 14 as better support for the combination of JIT optimization and highly-partitioned data ;-)
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