Re: SQL/JSON: functions

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Himanshu Upadhyaya <upadhyaya(dot)himanshu(at)gmail(dot)com>
Cc: Nikita Glukhov <n(dot)gluhov(at)postgrespro(dot)ru>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Oleg Bartunov <obartunov(at)postgrespro(dot)ru>, Erik Rijkers <er(at)xs4all(dot)nl>
Subject: Re: SQL/JSON: functions
Date: 2022-03-02 15:19:43
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On 3/1/22 16:41, Andrew Dunstan wrote:
> 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;
> andrew=# create table abc (x text, y json);
> andrew=# \d abc
>                Table ""
>  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.

I have confirmed that this is not required at all for the JSON_TABLE
patch set.

I'll submit new patch sets omitting it shortly. The GUC patch can be
considered separately, probably as release 16 material, but I think as
is it's at best quite incomplete.



Andrew Dunstan

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