2015-06-03 19:36:26 mw1148 wikidatawiki exception INFO: [8ae26643] /w/api.php?rcprop=user%7Ccomment%7Ctimestamp%7Ctitle%7Cids%7Csizes%7Credirect%7Cloginfo%7Cflags&maxlag=5&format=json&rclimit=5&list=recentchanges&rcnamespace=6%7C7&rcshow=&continue=&meta=userinfo&indexpageids=&action=query&uiprop=blockinfo%7Chasmsg   DBQueryError from line 1276 of /srv/mediawiki/php-1.26wmf8/includes/db/Database.php: A database error has occurred. Did you forget to run maintenance/update.php after upgrading?  See: https://www.mediawiki.org/wiki/Manual:Upgrading#Run_the_update_script
Query: SELECT  rc_id,rc_timestamp,rc_namespace,rc_title,rc_cur_id,rc_type,rc_deleted,rc_this_oldid,rc_last_oldid,rc_comment,rc_user,rc_user_text,rc_minor,rc_type,rc_bot,rc_old_len,rc_new_len,rc_logid,rc_log_type,rc_log_action,rc_params,page_is_redirect  FROM `recentchanges` FORCE INDEX (rc_timestamp) LEFT JOIN `page` ON ((rc_namespace=page_namespace) AND (rc_title=page_title))  WHERE rc_namespace IN ('6','7')  AND rc_type IN ('0','1','3')   ORDER BY rc_timestamp DESC,rc_id DESC LIMIT 6  
Function: ApiQueryRecentChanges::run
Error: 2013 Lost connection to MySQL server during query (10.64.16.144)

#0 /srv/mediawiki/php-1.26wmf8/includes/db/Database.php(1214): DatabaseBase->reportQueryError()
#1 /srv/mediawiki/php-1.26wmf8/includes/db/Database.php(1756): DatabaseBase->query()
#2 /srv/mediawiki/php-1.26wmf8/includes/api/ApiQueryBase.php(376): DatabaseBase->select()
#3 /srv/mediawiki/php-1.26wmf8/includes/api/ApiQueryRecentChanges.php(367): ApiQueryBase->select()
#4 /srv/mediawiki/php-1.26wmf8/includes/api/ApiQueryRecentChanges.php(131): ApiQueryRecentChanges->run()
#5 /srv/mediawiki/php-1.26wmf8/includes/api/ApiQuery.php(286): ApiQueryRecentChanges->execute()
#6 /srv/mediawiki/php-1.26wmf8/includes/api/ApiMain.php(1131): ApiQuery->execute()
#7 /srv/mediawiki/php-1.26wmf8/includes/api/ApiMain.php(469): ApiMain->executeAction()
#8 /srv/mediawiki/php-1.26wmf8/includes/api/ApiMain.php(442): ApiMain->executeActionWithErrorHandling()
#9 /srv/mediawiki/php-1.26wmf8/api.php(88): ApiMain->execute()
#10 /srv/mediawiki/w/api.php(3): include()
#11 {main} {"private":false}

mysql> EXPLAIN SELECT  rc_id,rc_timestamp,rc_namespace,rc_title,rc_cur_id,rc_type,rc_deleted,rc_this_oldid,rc_last_oldid,rc_comment,rc_user,rc_user_text,rc_minor,rc_type,rc_bot,rc_old_len,rc_new_len,rc_logid,rc_log_type,rc_log_action,rc_params,page_is_redirect  FROM `recentchanges` FORCE INDEX (rc_timestamp) LEFT JOIN `page` ON ((rc_namespace=page_namespace) AND (rc_title=page_title))  WHERE rc_namespace IN ('6','7')  AND rc_type IN ('0','1','3')   ORDER BY rc_timestamp DESC,rc_id DESC LIMIT 6\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: recentchanges
         type: index
possible_keys: NULL
          key: rc_timestamp
      key_len: 16
          ref: NULL
         rows: 6
        Extra: Using where
*************************** 2. row ***************************
           id: 1
  select_type: SIMPLE
        table: page
         type: eq_ref
possible_keys: name_title
          key: name_title
      key_len: 261
          ref: wikidatawiki.recentchanges.rc_namespace,wikidatawiki.recentchanges.rc_title
         rows: 1
        Extra: 
2 rows in set (0.02 sec)

Execution time:
Empty set (20.50 sec)

PAGER set to stdout
+----------------------------+---------+
| Variable_name              | Value   |
+----------------------------+---------+
| Handler_commit             | 1       |
| Handler_delete             | 0       |
| Handler_discover           | 0       |
| Handler_external_lock      | 0       |
| Handler_icp_attempts       | 0       |
| Handler_icp_match          | 0       |
| Handler_mrr_init           | 0       |
| Handler_mrr_key_refills    | 0       |
| Handler_mrr_rowid_refills  | 0       |
| Handler_prepare            | 0       |
| Handler_read_first         | 0       |
| Handler_read_key           | 0       |
| Handler_read_last          | 1       |
| Handler_read_next          | 0       |
| Handler_read_prev          | 6847234 |
| Handler_read_rnd           | 0       |
| Handler_read_rnd_deleted   | 0       |
| Handler_read_rnd_next      | 0       |
| Handler_rollback           | 0       |
| Handler_savepoint          | 0       |
| Handler_savepoint_rollback | 0       |
| Handler_tmp_update         | 0       |
| Handler_tmp_write          | 0       |
| Handler_update             | 0       |
| Handler_write              | 0       |
+----------------------------+---------+
25 rows in set (0.00 sec)

mysql> SHOW PROFILE FOR QUERY 2;
+----------------------+-----------+
| Status               | Duration  |
+----------------------+-----------+
| starting             |  0.000133 |
| checking permissions |  0.000009 |
| checking permissions |  0.000007 |
| Opening tables       |  0.000023 |
| After opening tables |  0.000010 |
| System lock          |  0.000008 |
| Table lock           |  0.000066 |
| After table lock     |  0.000009 |
| init                 |  0.000050 |
| optimizing           |  0.000021 |
| statistics           |  0.000034 |
| preparing            |  0.000034 |
| executing            |  0.000007 |
| Sorting result       |  0.000010 |
| Sending data         | 22.417293 |
| end                  |  0.000028 |
| query end            |  0.000013 |
| closing tables       |  0.000029 |
| freeing items        |  0.000017 |
| updating status      |  0.000033 |
| logging slow query   |  0.000014 |
| cleaning up          |  0.000012 |
+----------------------+-----------+
22 rows in set (0.00 sec)

mysql> EXPLAIN SELECT  rc_id,rc_timestamp,rc_namespace,rc_title,rc_cur_id,rc_type,rc_deleted,rc_this_oldid,rc_last_oldid,rc_comment,rc_user,rc_user_text,rc_minor,rc_type,rc_bot,rc_old_len,rc_new_len,rc_logid,rc_log_type,rc_log_action,rc_params,page_is_redirect  FROM `recentchanges` LEFT JOIN `page` ON ((rc_namespace=page_namespace) AND (rc_title=page_title))  WHERE rc_namespace IN ('6','7')  AND rc_type IN ('0','1','3')   ORDER BY rc_timestamp DESC,rc_id DESC LIMIT 6\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: recentchanges
         type: range
possible_keys: rc_namespace_title,rc_ns_usertext,tmp_3
          key: rc_namespace_title
      key_len: 4
          ref: NULL
         rows: 2
        Extra: Using index condition; Using where; Using filesort
*************************** 2. row ***************************
           id: 1
  select_type: SIMPLE
        table: page
         type: eq_ref
possible_keys: name_title
          key: name_title
      key_len: 261
          ref: wikidatawiki.recentchanges.rc_namespace,wikidatawiki.recentchanges.rc_title
         rows: 1
        Extra: 
2 rows in set (0.15 sec)

Execution time:
Empty set (0.00 sec)

PAGER set to stdout
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| Handler_commit             | 1     |
| Handler_delete             | 0     |
| Handler_discover           | 0     |
| Handler_external_lock      | 0     |
| Handler_icp_attempts       | 0     |
| Handler_icp_match          | 0     |
| Handler_mrr_init           | 0     |
| Handler_mrr_key_refills    | 0     |
| Handler_mrr_rowid_refills  | 0     |
| Handler_prepare            | 0     |
| Handler_read_first         | 0     |
| Handler_read_key           | 2     |
| Handler_read_last          | 0     |
| Handler_read_next          | 0     |
| Handler_read_prev          | 0     |
| Handler_read_rnd           | 0     |
| Handler_read_rnd_deleted   | 0     |
| Handler_read_rnd_next      | 0     |
| Handler_rollback           | 0     |
| Handler_savepoint          | 0     |
| Handler_savepoint_rollback | 0     |
| Handler_tmp_update         | 0     |
| Handler_tmp_write          | 0     |
| Handler_update             | 0     |
| Handler_write              | 0     |
+----------------------------+-------+
25 rows in set (0.00 sec)

mysql> SHOW PROFILE FOR QUERY 6;
+----------------------+----------+
| Status               | Duration |
+----------------------+----------+
| starting             | 0.000127 |
| checking permissions | 0.000010 |
| checking permissions | 0.000008 |
| Opening tables       | 0.000037 |
| After opening tables | 0.000011 |
| System lock          | 0.000009 |
| Table lock           | 0.000009 |
| After table lock     | 0.000010 |
| init                 | 0.000059 |
| optimizing           | 0.000025 |
| statistics           | 0.000126 |
| preparing            | 0.000043 |
| executing            | 0.000009 |
| Sorting result       | 0.000046 |
| Sending data         | 0.000040 |
| end                  | 0.000010 |
| query end            | 0.000012 |
| closing tables       | 0.000013 |
| freeing items        | 0.000012 |
| updating status      | 0.000033 |
| cleaning up          | 0.000009 |
+----------------------+----------+
21 rows in set (0.00 sec)

SELECT  rc_id,rc_timestamp,rc_namespace,rc_title,rc_cur_id,rc_type,rc_deleted,rc_this_oldid,rc_last_oldid,rc_comment,rc_user,rc_user_text,rc_minor,rc_type,rc_bot,rc_old_len,rc_new_len,rc_logid,rc_log_type,rc_log_action,rc_params,page_is_redirect  FROM `recentchanges` FORCE INDEX (rc_timestamp) LEFT JOIN `page` ON ((rc_namespace=page_namespace) AND (rc_title=page_title)) 

 -- rc_type will usually be like this. I don't think it'll ever be omitted, but could include all known types.
 WHERE rc_type IN ('0','1','3')
 -- rc_namespace could have anywhere from one namespace to all of them, or this might be omitted entirely.
 -- The bit after the AND might be omitted, although that should be relatively rare when rc_namespace isn't also omitted.
 WHERE rc_namespace IN ('0','1') AND (rc_type != 3 OR (rc_deleted & 1) != 1)
 -- This sort of thing comes from continuation, and i'd guess would be fairly common.
 WHERE rc_timestamp < '20150101000000' OR (rc_timestamp = '20150101000000' AND rc_id <= 123456)
 -- Ranges on rc_timestamp are possible.
 WHERE rc_timestamp <= '20150101000000'
 WHERE rc_timestamp >= '20140101000000'
 WHERE rc_timestamp <= '20150101000000' AND rc_timestamp >= '20140101000000'
 -- Any of these might be included (in any combination), each as = 0 or != 0.
 WHERE rc_minor = 0
 WHERE rc_bot = 0
 WHERE rc_patrolled = 0
 WHERE rc_user = 0
 -- Can test for a user, by name. The rc_deleted bit might be omitted, but that'd be uncommon.
 WHERE rc_user_text = 'Example' AND (rc_deleted & 4) != 4
 WHERE rc_user_text != 'Example' AND (rc_deleted & 4) != 4
 -- Might include this.
 WHERE rc_this_oldid = page_latest
 -- Might even include this.
 INNER JOIN change_tag ON (rc_id=ct_rc_id)
 WHERE ct_tag IN ('...')

 -- LIMIT could be anything from 2 to 5001. Ordering could be ASC.
 ORDER BY rc_timestamp DESC,rc_id DESC LIMIT 6