So, this turns out trickier than I thought. logging has these indexes:

KEY `type_time` (`log_type`,`log_timestamp`),
KEY `user_time` (`log_user`,`log_timestamp`),
KEY `page_time` (`log_namespace`,`log_title`,`log_timestamp`),
KEY `times` (`log_timestamp`),
KEY `log_page_id_time` (`log_page`,`log_timestamp`),
KEY `log_user_text_time` (`log_user_text`(16),`log_timestamp`),
KEY `log_title_time` (`log_title`(16),`log_timestamp`),
KEY `log_user_type_time` (`log_user`,`log_type`,`log_timestamp`),
KEY `log_title_type_time` (`log_title`(16),`log_type`,`log_timestamp`)

Since we need to select by type (delete) the natural index would be type_time. But then we need to link it to archive table (presumably to index only those who have archive entries) but archive table is:

KEY `name_title_timestamp` (`ar_namespace`,`ar_title`,`ar_timestamp`),
KEY `usertext_timestamp` (`ar_user_text`,`ar_timestamp`),
KEY `ar_revid` (`ar_rev_id`)

i.e. there is no index to link it to logging table for specific deletion. We could use namespace+title, but that produces bad query according to explain.

In general, it is not clear which entries we want to get, since half of the info seems to be in logging table (timestamp) and half in the archive table. Should we use only the logging table and ignore archive altogether, even with the risk that the page has been restored since and so should not be deleted? Note that if somebody deletes two revisions and then restores one (not necessarily the latest!) then the page would both have logging delete entry (actually, two of them) and archive entry, all under the same page ID. Not entirely clear what should happen in this case and how we should handle these deletes.

Change 374416 had a related patch set uploaded (by Smalyshev; owner: Smalyshev):
[mediawiki/extensions/CirrusSearch@master] Use correct table to find deletes.

https://gerrit.wikimedia.org/r/374416

Change 374416 merged by jenkins-bot:
[mediawiki/extensions/CirrusSearch@master] Use correct table to find deletes.

https://gerrit.wikimedia.org/r/374416