I use SQLDelight's MySQL dialect on my server. Recently I plan to migrate a table to combine many fields into a JSON field so the server code no longer needs to know the complex data structure. As part of the migration, I need to do something like this during runtime - when the sever sees a client with the new version, it knows the client won't access the old table anymore, so it's safe to migrate the record to new table.

INSERT OR IGNORE INTO new_table SELECT id, a, b, JSON_OBJECT('c', c, 'd', JSON_OBJECT(…)) FROM old_table WHERE id = ?;

The only problem is - Unlike the SQLite dialect, the MySQL dialect doesn't recognize JSON_OBJECT or other JSON expressions, even though in this case it doesn't have to - no matter how complex the query is, the result is not passed back to Kotlin.

I wish I could add the feature by myself, but I'm pretty new to Kotlin. So my question is: is there a way to evade the rigid syntax check? I could also retrieve from old table, convert the format in Kotlin, then write to the new table, but that would take hundreds of lines of complex code, instead of just one INSERT.

CodePudding user response：

I assume from your links you're on the alpha releases already, in alpha03 you can add currently unsupported behaviour by creating a local SQLDelight module (see this example) and adding the JSON_OBJECT to the functionType override. Also new function types are one of the easiest things to contribute up to SQLDelight so if you want it in the next release