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: 2022-03-01 21:41:38
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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}');
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;
(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.



Andrew Dunstan

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