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

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