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Re: SQL/JSON: functions

Andrew Dunstan <andrew@dunslane.net>

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From: Andrew Dunstan <andrew@dunslane.net>
To: Himanshu Upadhyaya <upadhyaya.himanshu@gmail.com>
Cc: Nikita Glukhov <n.gluhov@postgrespro.ru>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Dmitry Dolgov <9erthalion6@gmail.com>, Oleg Bartunov <obartunov@postgrespro.ru>, Erik Rijkers <er@xs4all.nl>
Date: 2022-03-01T21:41:38Z
Lists: pgsql-hackers 
On 2/1/22 14:11,I wrote:
>
> 2. The new GUC "sql_json" is a bit of a worry. I understand what it's
> trying to do, but I'm trying to convince myself it's not going to be a
> fruitful source of error reports, especially if people switch it in the
> middle of a session. Maybe it should be an initdb option instead of a GUC?
>
>


So far my efforts have not borne fruit. Here's why:


andrew=# set sql_json = jsonb;
SET
andrew=# create table abc (x text, y json);
CREATE TABLE
andrew=# \d abc
               Table "public.abc"
 Column | Type | Collation | Nullable | Default
--------+------+-----------+----------+---------
 x      | text |           |          |
 y      | json |           |          |

andrew=# insert into abc values ('a','{"q":1}');
INSERT 0 1
andrew=# select json_each(y) from abc;
ERROR:  function json_each(json) does not exist
LINE 1: select json_each(y) from abc;
               ^
HINT:  No function matches the given name and argument types. You might
need to add explicit type casts.
andrew=# select jsonb_each(y) from abc;
 jsonb_each
------------
 (q,1)
(1 row)


The description tells them the column is json, but the json_* functions
don't work on the column and you need to use the jsonb functions. That
seems to me a recipe for major confusion. It might be better if we set
it at initdb time so it couldn't be changed, but even so it could be
horribly confusing.

This is certainly severable from the rest of these patches. I'm not sure
how severable it is from the SQL/JSON Table patches.


cheers


andrew

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

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. JSON_TABLE: Add support for NESTED paths and columns

  2. Add basic JSON_TABLE() functionality

  3. Add SQL/JSON query functions

  4. Add soft error handling to some expression nodes

  5. Adjust populate_record_field() to handle errors softly

  6. Refactor code used by jsonpath executor to fetch variables

  7. Add more SQL/JSON constructor functions

  8. SQL/JSON: support the IS JSON predicate

  9. SQL/JSON: add standard JSON constructor functions

  10. Improve readability of SQL/JSON documentation.

  11. Documentation for SQL/JSON features

  12. RETURNING clause for JSON() and JSON_SCALAR()

  13. SQL JSON functions

  14. SQL/JSON query functions

  15. IS JSON predicate

  16. SQL/JSON constructors

  17. Common SQL/JSON clauses

  18. Doc: remove obsolete entries in table of BRIN strategy numbers.

  19. Doc: standardize markup a bit more.

  20. Make pg_regress.c unset PGDATABASE during make installcheck.

  21. Fix handling of GENERATED columns in CREATE TABLE LIKE INCLUDING DEFAULTS.