Horton

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

Andrew Dunstan <andrew@dunslane.net>

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From: Andrew Dunstan <andrew@dunslane.net>
To: "David G. Johnston" <david.g.johnston@gmail.com>, "David E. Wheeler" <david@justatheory.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Jeevan Chalke <jeevan.chalke@enterprisedb.com>
Date: 2024-06-13T19:53:17Z
Lists: pgsql-hackers

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  1. Teach jsonpath string() to unwrap in lax mode

On 2024-06-12 We 16:02, David G. Johnston wrote:
> On Sat, Jun 8, 2024 at 3:50 PM David E. Wheeler 
> <david@justatheory.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.
>
>

Hmm. You might be right. Many of these items have this code, but the 
string() branch does not:

    if (unwrap && JsonbType(jb) == jbvArray)
         return executeItemUnwrapTargetArray(cxt, jsp, jb, found,
                                             false);


cheers


andrew

--
Andrew Dunstan
EDB:https://www.enterprisedb.com