| From: | jian he <jian(dot)universality(at)gmail(dot)com> |
|---|---|
| To: | Andy Fan <zhihuifan1213(at)163(dot)com> |
| Cc: | Amit Langote <amitlangote09(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Erik Rijkers <er(at)xs4all(dot)nl>, Andres Freund <andres(at)anarazel(dot)de>, Andrew Dunstan <andrew(at)dunslane(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Peter Eisentraut <peter(at)eisentraut(dot)org> |
| Subject: | Re: remaining sql/json patches |
| Date: | 2024-03-07 04:08:21 |
| Message-ID: | CACJufxGtetrn34Hwnb9D2if5D_HOPAh235MtEZ1meVYx-BiNtg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Mar 5, 2024 at 12:38 PM Andy Fan <zhihuifan1213(at)163(dot)com> wrote:
>
>
> In the commit message of 0001, we have:
>
> """
> Both JSON_VALUE() and JSON_QUERY() functions have options for
> handling EMPTY and ERROR conditions, which can be used to specify
> the behavior when no values are matched and when an error occurs
> during evaluation, respectively.
>
> All of these functions only operate on jsonb values. The workaround
> for now is to cast the argument to jsonb.
> """
>
> which is not clear for me why we introduce JSON_VALUE() function, is it
> for handling EMPTY or ERROR conditions? I think the existing cast
> workaround have a similar capacity?
>
I guess because it's in the standard.
but I don't see individual sql standard Identifier, JSON_VALUE in
sql_features.txt
I do see JSON_QUERY.
mysql also have JSON_VALUE, [1]
EMPTY, ERROR: there is a standard Identifier: T825: SQL/JSON: ON EMPTY
and ON ERROR clauses
[1] https://dev.mysql.com/doc/refman/8.0/en/json-search-functions.html#function_json-value
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