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From: David E. Wheeler <[email protected]>
To: Florents Tselai <[email protected]>
Cc: Alexander Korotkov <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: pgsql-hackers <[email protected]>
Subject: Re: PATCH: jsonpath string methods: lower, upper, initcap, l/r/btrim, replace, split_part
Date: Fri, 27 Sep 2024 10:45:23 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+v5N41ApiOdU6VyxaY0_8o=2LLmr_h20R-_am5DK0KxsV2tZg@mail.gmail.com>
References: <CA+v5N40sJF39m0v7h=QN86zGp0CUf9F1WKasnZy9nNVj_VhCZQ@mail.gmail.com>
	<[email protected]>
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On Sep 26, 2024, at 13:59, Florents Tselai <[email protected]> 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’s 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’ve 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’m 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

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