https://lists.wikimedia.org/pipermail/cloud/2019-November/000852.html

SQL

USE commonswiki_p;

SELECT log_timestamp AS first_upload,
    uploads,
    (
        SELECT actor_user
        FROM actor_logging
        WHERE actor_id = act
    ) AS username
FROM logging_userindex
INNER JOIN (
    SELECT MIN(log_id) AS first_upload_id,
        COUNT(log_timestamp) AS uploads,
        log_actor AS act
    FROM logging_userindex
    WHERE log_type = "upload"
    GROUP BY log_actor
) AS first_uploads
ON log_id = first_upload_id
AND log_id IN (
    SELECT ct_log_id
    FROM change_tag
    WHERE ct_tag_id = 21
);

/*

+------+--------------------+------------+--------+----------------------------------------------------------------------------+----------------------+---------+----------------------------------+----------+---------------------------------------------------------------------+
| id   | select_type        | table      | type   | possible_keys                                                              | key                  | key_len | ref                              | rows     | Extra                                                               |
+------+--------------------+------------+--------+----------------------------------------------------------------------------+----------------------+---------+----------------------------------+----------+---------------------------------------------------------------------+
|    1 | PRIMARY            | change_tag | ref    | change_tag_log_tag_id,change_tag_tag_id_id                                 | change_tag_tag_id_id | 4       | const                            |   371428 | Using where; Using index                                            |
|    1 | PRIMARY            | logging    | eq_ref | PRIMARY,type_time,log_type_action                                          | PRIMARY              | 4       | commonswiki.change_tag.ct_log_id |        1 | Using where                                                         |
|    1 | PRIMARY            | <derived3> | ref    | key0                                                                       | key0                 | 9       | commonswiki.change_tag.ct_log_id |       10 | Using where                                                         |
|    3 | DERIVED            | logging    | ref    | type_time,log_type_action                                                  | type_time            | 34      | const                            | 52691072 | Using index condition; Using where; Using temporary; Using filesort |
|    2 | DEPENDENT SUBQUERY | actor      | eq_ref | PRIMARY                                                                    | PRIMARY              | 8       | first_uploads.act                |        1 | Using where                                                         |
|    7 | DEPENDENT SUBQUERY | logging    | ref    | type_time,actor_time,log_actor_type_time,log_actor_deleted,log_type_action | actor_time           | 8       | commonswiki.actor.actor_id       | 97712560 | Using where                                                         |
+------+--------------------+------------+--------+----------------------------------------------------------------------------+----------------------+---------+----------------------------------+----------+---------------------------------------------------------------------+

*/
SQL

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