Horton

Shouldn't jsonpath .string() Unwrap?

David E. Wheeler <david@justatheory.com>

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From: "David E. Wheeler" <david@justatheory.com>
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-06-08T22:49:38Z
Lists: pgsql-hackers

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

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?

Best,

David

[1]: https://github.com/postgres/postgres/blob/REL_17_BETA1/src/test/regress/expected/jsonb_jsonpath.out#L2527-L2530