Properties created should be included as a statistic. Query that retrieves the info:
use wikidatawiki_p; SELECT actor_name AS 'User', COUNT(*) AS 'Properties created' FROM revision_userindex JOIN page ON rev_page = page_id JOIN actor ON rev_actor = actor_id WHERE page_namespace = 120 AND rev_parent_id = 0 GROUP BY rev_actor
I ran it a few times, and it took between 3.5 seconds and just under a minute. Combined with caching, it should be pretty fast
This is similar to T171996 in that the architecture currently revolves solely around logged actions. We can add in extra queries for sure, it just might require a lot of reworking of the code.
Admin Stats surprisingly runs pretty fast on Wikidata. I'm guessing there a lot fewer logged actions than other wikis like English Wikipedia (at least fewer admins). https://xtools.wmflabs.org/adminstats/www.wikidata.org/2019-04-25/2020-04-25 (maximum date range) ran in just 4.5 seconds, so I think we can afford the query for properties created.
I won't have time to work on this for a while but I'm more than happy to do code review.
Not without some major reworking, no. The actions reported in AdminStats come from a configuration file where you specify the log type and log action – nothing more. We'll need some custom handling to support properties created, but if/when we do this then yes, I think using the page creation log will probably be more efficient (though the data only goes back to June 2018).