AFAIK disabled for performance reasons.
"Shows a list of people who contributed to the page in question using the real name specified in the user's preferences. Currently disabled on Wikimedia wikis, but is enabled by default on vanilla MediaWiki."
https://translatewiki.net/w/i.php?title=Translating:MediaWiki&action=credits
Version: unspecified
Severity: enhancement
See Also:
| Status | Subtype | Assigned | Task | ||
|---|---|---|---|---|---|
| Open | Feature | None | T40450 Reimplement MediaWiki's info action (tracking) | ||
| Open | Feature | None | T41533 Include action=credits output into action=info as well | ||
| Open | None | T87268 Copyright license and attribution issues (tracking) | |||
| Open | Feature | None | T30064 Collection extension needs some way to credit original authors of a work | ||
| Open | Feature | None | T49721 Restore action=credits on Wikimedia wikis | ||
| Duplicate | None | T49722 Make action=credits faster | |||
| Open | Feature | None | T49723 Cache action=credits results | ||
| Resolved | Dereckson | T130820 Enable action=credits on test and or beta |
https://github.com/wikimedia/mediawiki/blob/master/includes/page/WikiPage.php#L1000
I presume caching is needed, but not enough (example for Paris on enwiki)
mysql:wikiadmin@db1072 [enwiki]> EXPLAIN SELECT rev_user AS user_id,rev_user_text AS user_name,user_real_name,MAX(rev_timestamp) AS timestamp FROM `revision` LEFT JOIN `user` ON ((rev_user = user_id)) WHERE rev_page = 22989 AND (rev_user_text != '110.171.37.207') AND ((rev_deleted & 4) = 0) GROUP BY rev_user,rev_user_text ORDER BY timestamp DESC; +------+-------------+----------+--------+-----------------------------------------------+----------------+---------+--------------------------+-------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +------+-------------+----------+--------+-----------------------------------------------+----------------+---------+--------------------------+-------+----------------------------------------------+ | 1 | SIMPLE | revision | ref | rev_page_id,page_timestamp,usertext_timestamp | page_timestamp | 4 | const | 27090 | Using where; Using temporary; Using filesort | | 1 | SIMPLE | user | eq_ref | PRIMARY | PRIMARY | 4 | enwiki.revision.rev_user | 1 | | +------+-------------+----------+--------+-----------------------------------------------+----------------+---------+--------------------------+-------+----------------------------------------------+ 2 rows in set (0.09 sec) mysql:wikiadmin@db1072 [enwiki]>
So taking a quick look at this it looks like the expensive bit here is the getContributors method in CreditsAction which calls WikiPage::getContributors which will hit the db every time.
In theory this should be easy to cache in some way