Hi !
I have created simply plugin which allows administrator to assign country to K2 Item.
Country is stored in k2_item table (column plugins) in json format.

Is there any way to filter category items by country using events like onK2PrepareContent etc. ?

Thanks for help.

Hi. No unfortunately you cannot search by JSON. You will have to modify your plugin to use it's own database so you can add extra queries. A more simple solution would be to use extra fields and use an extension which can filter items based on extra fields.

Thanks for the answer.
I have one more question. Is possible to override or modify method (db query) which retrieves items from database without hacking k2 core files?
Thanks.

No currently this is not an easy task. I think it would be more easy to duplicate the K2 view ( or module ) you wish to modify and then modify the code there.