On 2016-01-11 22:06, gnosygnu wrote:
So, to answer your question, the IDs never change. 14640471 will always point to Mars, while 699008434 points to the 2016-01-09 revision for Mars.
While it's unlikely/rare, I think the page id can change when a page is deleted and re-created, and maybe some other cases. MediaWiki tries to keep it constant (for example, I think it's preserved after deletion and undeletion), but it's not always possible. It should be fine to use to track pages across renames, though, at least most of the time.
That said, different dumps will have different revision_ids, because an article may be updated. If Mars gets updated tomorrow, and the English Wikipedia dump is generated afterwards, then that dump will list Mars with a new revision_id (something higher than 6999008434).
Please don't assume that revision id's are increasing. Weird things can happen with import, export and page history merges :)