Re: PG 15 (and to a smaller degree 14) regression due to ExprEvalStep size

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Andres Freund <andres(at)anarazel(dot)de>, Michael Paquier <michael(at)paquier(dot)xyz>, John Naylor <john(dot)naylor(at)enterprisedb(dot)com>, "Jonathan S(dot) Katz" <jkatz(at)postgresql(dot)org>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, David Rowley <dgrowleyml(at)gmail(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Nikita Glukhov <n(dot)gluhov(at)postgrespro(dot)ru>
Subject: Re: PG 15 (and to a smaller degree 14) regression due to ExprEvalStep size
Date: 2022-07-18 19:09:39
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On 2022-07-15 Fr 17:07, Andres Freund wrote:
> Hi,
> On 2022-07-08 17:05:49 -0400, Andrew Dunstan wrote:
>> On 2022-07-05 Tu 15:04, Andrew Dunstan wrote:
>>> On 2022-07-05 Tu 14:36, Andres Freund wrote:
>>>>>> I think Andrew's beta 2 comment was more about my other architectural
>>>>>> complains around the json expression eval stuff.
>>>>> Right. That's being worked on but it's not going to be a mechanical fix.
>>>> Any updates here?
>>> Not yet. A colleague and I are working on it. I'll post a status this
>>> week if we can't post a fix.
>> We're still working on it. We've made substantial progress but there are
>> some tests failing that we need to fix.
> I think we need to resolve this soon - or consider the alternatives. A lot of
> the new json stuff doesn't seem fully baked, so I'm starting to wonder if we
> have to consider pushing it a release further down.
> Perhaps you could post your current state? I might be able to help resolving
> some of the problems.

Ok. Here is the state of things. This has proved to be rather more
intractable than I expected. Almost all the legwork here has been done
by Amit Langote, for which he deserves both my thanks and considerable
credit, but I take responsibility for it.

I just discovered today that this scheme is failing under
"force_parallel_mode = regress". I have as yet no idea if that can be
fixed simply or not. Apart from that I think the main outstanding issue
is to fill in the gaps in llvm_compile_expr().

If you have help you can offer that would be very welcome.

I'd still very much like to get this done, but if the decision is we've
run out of time I'll be sad but understand.



Andrew Dunstan

Attachment Content-Type Size
0001-in-JsonExprState-just-store-a-pointer-to-the-input-F.patch text/x-patch 2.2 KB
0002-Evaluate-various-JsonExpr-sub-expressions-using-pare.patch text/x-patch 35.5 KB
0003-Use-one-ExprState-to-implement-JsonItemCoercions.patch text/x-patch 17.1 KB

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