The new page move code violates the unique index on namespace+title when renaming a page over a
redirect.

Steps to reproduce:

1. Create page 'First title'
2. Move 'First title' to 'Second title'
3. Move 'Second title' to 'First title'

Actual behavior: Database error.

Expected behavior: The 'First title' and 'Second title' cur entries should have their titles swapped, and the
redirect rewritten appropriately.

Failed query:

UPDATE cur SET cur_touched='20041207081745',cur_namespace='0',cur_title='First_title' WHERE
cur_id='948'

from within function "Title::moveOverExistingRedirect". MySQL returned error "1062: Duplicate entry '0-
First_title' for key 2".

Version: 1.4.x
Severity: normal