Bug #103692 Can't use -> or ->> with a user defined variable

• Submitted: 14 May 2021 0:33
• Modified: 14 May 2021 6:34
• Reporter: Justin Levene
• Status: Verified
• Category: MySQL Server: JSON
• Severity: S4 (Feature request)
• Version: 8.0.23, 8.0.25
• OS: Any
• CPU Architecture: Any

[14 May 2021 0:33] Justin Levene

Description:
Using -> or ->> wwith a user defined @ variable isn't allowed.

Also I reported in another bug report, the path can't be a variable or a concat() function. etc.

How to repeat:
set @js = '{"a":"99", "b":"2"}';
set @js = json_object("a",99, "b",2);

select @js->>"$.a";

Using either set won't work, and as this is an alias for json_extract, the following works:

select json_extract(@js, "$.a");

Suggested fix:
To work like json_extract as documented

[14 May 2021 6:34] MySQL Verification Team

Hello Justin Levene,

Thank you for the report and feedback.

regards,
Umesh

[14 May 2021 12:05] Knut Anders Hatlen

It looks like this was an intentional limitation of the original implementation of this syntax.

Both WL#8607 (the -> operator) and WL#9124 (the ->> operator) say under "High Level Architecture":

> f1       is a column identifier, general expressions aren't supported

Since it works as designed, I've recategorized the report from bug to feature request.