From: Tom Lane <tgl@sss.pgh.pa.us>
To: Corey Huinker <corey.huinker@gmail.com>
cc: Jeff Davis <pgsql@j-davis.com>, Magnus Hagander <magnus@hagander.net>,
        Stephen Frost <sfrost@snowman.net>,
        Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>,
        Matthias van de Meent <boekewurm+postgres@gmail.com>,
        Peter Smith <smithpb2250@gmail.com>,
        PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
        Tomas Vondra <tomas.vondra@enterprisedb.com>
Subject: Re: Statistics Import and Export
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Comments: In-reply-to Corey Huinker <corey.huinker@gmail.com>
	message dated "Wed, 03 Apr 2024 14:13:04 -0400"
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Date: Wed, 03 Apr 2024 16:02:47 -0400
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Corey Huinker <corey.huinker@gmail.com> writes:
>> As far as that goes, it shouldn't be that hard to deal with, at least
>> not for "soft" errors which hopefully cover most input-function
>> failures these days.  You should be invoking array_in via
>> InputFunctionCallSafe and passing a suitably-set-up ErrorSaveContext.
>> (Look at pg_input_error_info() for useful precedent.)

> Ah, my understanding may be out of date. I was under the impression that
> that mechanism relied on the the cooperation of the per-element input
> function, so even if we got all the builtin datatypes to play nice with
> *Safe(), we were always going to be at risk with a user-defined input
> function.

That's correct, but it's silly not to do what we can.  Also, I imagine
that there is going to be high evolutionary pressure on UDTs to
support soft error mode for COPY, so over time the problem will
decrease --- as long as we invoke the soft error mode.

> 1. NULL input =>  Return NULL. (because strict).
> 2. Actual error (permissions, cache lookup not found, etc) => Raise ERROR
> (thus ruining binary upgrade)
> 3. Call values are so bad (examples: attname not found, required stat
> missing) that nothing can recover => WARN, return FALSE.
> 4. At least one stakind-stat is wonky (impossible for datatype, missing
> stat pair, wrong type on input parameter), but that's the worst of it => 1
> to N WARNs, write stats that do make sense, return TRUE.
> 5. Hunky-dory. => No warns. Write all stats. return TRUE.

> Which of those seem like good ereturn candidates to you?

I'm good with all those behaviors.  On reflection, the design I was
vaguely imagining wouldn't cope with case 4 (multiple WARNs per call)
so never mind that.

			regards, tom lane