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Subject: Re: PATCH: jsonpath string methods: lower, upper, initcap, l/r/btrim,
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From: "David E. Wheeler" <david@justatheory.com>
In-Reply-To: <CA+v5N41ApiOdU6VyxaY0_8o=2LLmr_h20R-_am5DK0KxsV2tZg@mail.gmail.com>
Date: Fri, 27 Sep 2024 10:45:23 +0100
Cc: Alexander Korotkov <aekorotkov@gmail.com>,
 Tom Lane <tgl@sss.pgh.pa.us>,
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To: Florents Tselai <florents.tselai@gmail.com>
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On Sep 26, 2024, at 13:59, Florents Tselai <florents.tselai@gmail.com> =
wrote:

> Speaking of extensible: the jsonpath standard does mention function =
extensions [1] ,
> so it looks like we're covered by the standard, and the mutability =
aspect is an implementation detail. No?

That=E2=80=99s not the standard used for Postgres jsonpath. Postgres =
follows the SQL/JSON standard in the SQL standard, which is not publicly =
available, but a few people on the list have copies they=E2=80=99ve =
purchased and so could provide some context.

In a previous post I wondered if the SQL standard had some facility for =
function extensions, but I suspect not. Maybe in the next iteration?

> And having said that, the whole jsonb/jsonpath parser/executor =
infrastructure is extremely powerful
> and kinda under-utilized if we use it "only" for jsonpath.
> Tbh, I can see it supporting more specific DSLs and even offering =
hooks for extensions.
> And I know for certain I'm not the only one thinking about this.
> See [2] for example where they've lifted, shifted and renamed the =
jsonb/jsonpath infra to build a separate language for graphs

I=E2=80=99m all for extensibility, though jsonpath does need to continue =
to comply with the SQL standard. Do you have some idea of the sorts of =
hooks that would allow extension authors to use some of that underlying =
capability?

Best,

David