Re: Shouldn't jsonpath .string() Unwrap?

From: "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>
To: "David E(dot) Wheeler" <david(at)justatheory(dot)com>, andrew(at)dunslane(dot)net
Cc: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Shouldn't jsonpath .string() Unwrap?
Date: 2024-06-12 20:02:44
Message-ID: CAKFQuwacXyOuRCkQZaJmzXu2jkPz629GFZS2AdjZa8T32FKDow@mail.gmail.com
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On Sat, Jun 8, 2024 at 3:50 PM David E. Wheeler <david(at)justatheory(dot)com>
wrote:

> Hackers,
>
> Most of the jsonpath methods auto-unwrap in lax mode:
>
> david=# select jsonb_path_query('[-2,5]', '$.abs()');
> jsonb_path_query
> ------------------
> 2
> 5
> (2 rows)
>
> The obvious exceptions are size() and type(), which apply directly to
> arrays, so no need to unwrap:
>
> david=# select jsonb_path_query('[-2,5]', '$.size()');
> jsonb_path_query
> ------------------
> 2
> (1 row)
>
> david=# select jsonb_path_query('[-2,5]', '$.type()');
> jsonb_path_query
> ------------------
> "array"
>
> But what about string()? Is there some reason it doesn’t unwrap?
>
> david=# select jsonb_path_query('[-2,5]', '$.string()');
> ERROR: jsonpath item method .string() can only be applied to a bool,
> string, numeric, or datetime value
>
> What I expect:
>
> david=# select jsonb_path_query('[-2,5]', '$.string()');
> jsonb_path_query
> —————————
> "2"
> "5"
> (2 rows)
>
> However, I do see a test[1] for this behavior, so maybe there’s a reason
> for it?
>
>
Adding Andrew.

I'm willing to call this an open item against this feature as I don't see
any documentation explaining that string() behaves differently than the
others.

David J.

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