* (
bug 25734) API: possible issue with revids validation
It seems, on databases with loads of revision rows (ie enwiki, not testwiki), although the EXPLAIN is sane, it's doing something stupid (table scan? I've nfi). So, as any revision id's less than 0 aren't valid, just prefilter them from the database SQL query
mysql> DESCRIBE SELECT /* ApiPageSet::initFromRevIDs */ rev_id,rev_page FROM `revision`,`page` WHERE rev_id IN ('10','20','30','40','-50','60') AND (rev_page = page_id);
+----+-------------+----------+-------+-------------------------------+---------+---------+-----------------------+-------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+----------+-------+-------------------------------+---------+---------+-----------------------+-------+--------------------------+
| 1 | SIMPLE | page | index | PRIMARY | PRIMARY | 4 | NULL | 22982 | Using index |
| 1 | SIMPLE | revision | ref | PRIMARY,rev_id,page_timestamp | PRIMARY | 4 | testwiki.page.page_id | 1 | Using where; Using index |
+----+-------------+----------+-------+-------------------------------+---------+---------+-----------------------+-------+--------------------------+