A canadian citizen can enter Poland for 90 days within 180 days just with a valid passport.
But can this citizen extend his stay as a tourist up to 180 days by asking a D type while IN Poland without having to go back to it's country ?
Or does he/she have to go back to Canada to obtain the D visa.
Is there any other means to achieve that ? (Legal)
Yes, it's possible: forummigracyjne.org/files/180/ulotka_wizy_en.pdf
National visa may be extend by provincial governor (Wojewoda).
He/she can only renew the residence visa issued by the consul if the foreigner fulfils specific requirements.