On Mon, Jan 11, 2016 at 10:37 PM, Bartosz Dziewoński matma.rex@gmail.com wrote:
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.
The patch to preserve IDs over undeletion was merged today (so don't expect IDs to be unchanging in older dumps). Also, pages can be split and joined through partial undeletion of revisions, in which case it is hard to tell what staying constant even means. You can swap the ID of any two pages, for example, without any changes in their text or history, with the right sequence of deletions, undeletions and page moves. Also, when a page is moved, the ID and the title are disassociated (which is probably what you'd want in that case).