Re: Error-safe user functions

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andrew Dunstan <andrew(at)dunslane(dot)net>
Cc: Amul Sul <sulamul(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Alexander Korotkov <aekorotkov(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Corey Huinker <corey(dot)huinker(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Joe Conway <mail(at)joeconway(dot)com>, Nikita Glukhov <n(dot)gluhov(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Error-safe user functions
Date: 2022-12-24 15:42:35
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Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> As I was giving this a final polish I noticed this in jspConvertRegexFlags:

>     /*
>      * We'll never need sub-match details at execution.  While
>      * RE_compile_and_execute would set this flag anyway, force it on here to
>      * ensure that the regex cache entries created by makeItemLikeRegex are
>      * useful.
>      */
>     cflags |= REG_NOSUB;

> Clearly the comment would no longer be true. I guess I should just
> remove this?

Yeah, we can just drop that I guess. I'm slightly worried that we might
need it again after some future refactoring; but it's not really worth
devising a re-worded comment to justify keeping it.

Also, I realized that I failed in my reviewerly duty by not noticing
that you'd forgotten to pg_regfree the regex after successful
compilation. Running something like this exposes the memory leak
very quickly:

select pg_input_is_valid('$ ? (@ like_regex "pattern" flag "smixq")', 'jsonpath')
from generate_series(1,10000000);

The attached delta patch takes care of it. (Per comment at pg_regcomp,
we don't need this after a failure return.)

regards, tom lane

Attachment Content-Type Size
dont-leak-compiled-regex.patch text/x-diff 466 bytes

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