Itwiki sysops, ordered by their "age" at the first time they were made sysop

This query sucks. But it works! (Or, does it?)
Several notes:
 - renamed users don't appear cleanly, or have duplicate entries, or user_registration is greather than log_timestamp
 - this should use actor

 - old users don't have user_registration (see e.g. T24097). For them we use the timestamp of the first edit, just like fixUserRegistration would do; to avoid a full table scan, the revision query is limited on rev_id using a hardcoded value
 - old rights log entries don't have params for added/removed groups... These are circumvented with a check on the summary.
- in old entries, the target (log_title) may start with a lowercase letter [0] or be 'User:User:username' [1]. This also breaks log entries on-wiki...

[0]: https://it.wikipedia.org/w/index.php?title=Speciale:Registri&offset=20060323000000&limit=1&type=rights&user=Gac&page=&wpdate=2006-03-22&tagfilter=&day=22&month=3&year=2006
[1]: https://it.wikipedia.org/wiki/Speciale:Registri?type=&user=&page=Utente%3AUtente%3AOrbiliusMagister&wpdate=&tagfilter=

SQL

use itwiki_p;
select user_name,
	@us_reg := COALESCE(
      user_registration,
      ( SELECT MIN(rev_timestamp) FROM revision WHERE rev_id < 2450000 AND rev_user = user_id )
    ) as registration,
    @sys_tim := log.log_timestamp as sysop_timestamp,
    DATEDIFF( @sys_tim, @us_reg ) as days
from user
right -- this should be a simple join, but a right join ensures that data is displayed even for users without registration
join (
  select
  log_timestamp, replace( replace( CONCAT( UCASE( CAST( LEFT( log_title, 1) as CHAR ) ), SUBSTRING( log_title, 2 ) ),'_', ' '), 'Utente:', '' ) as name
     from logging where
     	log_type = 'rights' and (
     		(
                cast(log_params as char) rlike 'newgroups.+sysop' and
     			(char_length(cast(log_params as char))-char_length(replace(cast(log_params as char), 'sysop','')) = char_length('sysop'))
            ) or cast(log_params as char) rlike '[^\n]*\n.*sysop'
          or ( log_timestamp < '20060613000000' and (select cast(comment_text as char) as summary from comment where comment_id = log_comment_id) rlike '[sS]ysop' )
        ) 
     group by name
     order by log_id
) as log on log.name = user.user_name
order by days

SQL

Checking query status...