I have a custom post type where the user can set a video 'url' custom field. I need to download meta-data about the video (e.g. title, description, thumbnail) and store it along with the rest of the post's data.
Since downloading this data can be a bit long, I'd like to do this only when it's necessary, i.e. when the 'url' field has changed.
Is there a way to check whether a field's value has changed on