MyISAM में अन्य पढ़ने को ब्लॉक क्यों पढ़ता है?

Question

मेरे पास एक बहुत लंबा चल रहा है। यह एक बार एक cronjob रन एक दिन है, लेकिन पूरे डीबी नीचे बंद कर दिया जाता है, जब यह चल रहा है:

mysql> show full processlist; 
+--------+------+-----------+------+---------+------+--------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 
| Id  | User | Host  | db | Command | Time | State  | Info                                                                                                                                                                                                                                                                | 
+--------+------+-----------+------+---------+------+--------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 
| 464971 | paul | localhost | paul | Sleep | 2264 |    | NULL                                                                                                                                                                                                                                                                | 
| 472177 | paul | localhost | paul | Sleep | 96 |    | NULL                                                                                                                                                                                                                                                                | 
| 479527 | paul | localhost | paul | Sleep | 1765 |    | NULL                                                                                                                                                                                                                                                                | 
| 479528 | paul | localhost | paul | Sleep | 1765 |    | NULL                                                                                                                                                                                                                                                                | 
| 479623 | paul | localhost | paul | Query | 83 | Locked  | SELECT `metaward_alias`.`id`, `metaward_alias`.`modified`, `metaward_alias`.`created`, `metaward_alias`.`string_id`, `metaward_alias`.`shortname`, `metaward_alias`.`remote_image`, `metaward_alias`.`image`, `metaward_alias`.`user_id`, `metaward_alias`.`type_id`, `metaward_alias`.`md5` FROM `metaward_alias` WHERE `metaward_alias`.`string_id` = 'http://profiles.us.playstation.com/playstation/psn/profiles/Kool_Aid_Dude27' ORDER BY `metaward_alias`.`modified` DESC                                                                                                                                             | 
| 479624 | paul | localhost | paul | Sleep | 82 |    | NULL                                                                                                                                                                                                                                                                | 
| 480057 | paul | localhost | paul | Query | 88 | Locked  | UPDATE `metaward_award` SET `modified` = '2009-09-16 02:12:37', `created` = '2009-09-08 12:06:44', `string_id` = 'isaw5t', `owner_id` = 1135, `name` = '50 online matches won', `description` = 'Aim to win 50 online matches. (ranked match)', `owner_points` = 50, `url` = 'http://live.xbox.com/en-US/profile/Achievements/ViewAchievementDetails.aspx?tid=%09%5d%3a%13%1f%5d%1fGt%06', `remote_image` = 'http://tiles.xbox.com/tiles/6G/dm/1oCLiGJhbC9CCxtyGy1TVkRBL2FjaC8wLzE2AAAAAOfn5-lJZ-Q=.jpg', `image` = 'award/isaw5t.png', `parent_award_id` = 115242, `slug` = '50-online-matches-won-1', `points` = 43.9 WHERE `metaward_award`.`id` = 116054                                                                                                  | 
| 480571 | paul | localhost | paul | Query | 84 | Locked  | SELECT `metaward_alias`.`id`, `metaward_alias`.`modified`, `metaward_alias`.`created`, `metaward_alias`.`string_id`, `metaward_alias`.`shortname`, `metaward_alias`.`remote_image`, `metaward_alias`.`image`, `metaward_alias`.`user_id`, `metaward_alias`.`type_id`, `metaward_alias`.`md5` FROM `metaward_alias` WHERE `metaward_alias`.`string_id` = 'http://live.xbox.com/en-US/profile/profile.aspx?GamerTag=Hendricks' ORDER BY `metaward_alias`.`modified` DESC                                                                                                                                               | 
| 480578 | paul | localhost | paul | Query | 86 | Locked  | UPDATE `metaward_alias` SET `modified` = '2009-09-16 02:12:38', `created` = '2009-09-09 01:21:08', `string_id` = 'http://live.xbox.com/en-US/profile/profile.aspx?GamerTag=jobbie%20man', `shortname` = 'jobbie man', `remote_image` = 'http://avatar.xboxlive.com/avatar/jobbie%20man/avatarpic-l.png', `image` = 'alias/2ec3d391a311be936d9603f99dcfa353.png', `user_id` = NULL, `type_id` = 1135, `md5` = '2ec3d391a311be936d9603f99dcfa353' WHERE `metaward_alias`.`id` = 705419                                                                                                                                            | 
| 480579 | paul | localhost | paul | Query | 88 | Locked  | SELECT `metaward_award`.`id`, `metaward_award`.`modified`, `metaward_award`.`created`, `metaward_award`.`string_id`, `metaward_award`.`owner_id`, `metaward_award`.`name`, `metaward_award`.`description`, `metaward_award`.`owner_points`, `metaward_award`.`url`, `metaward_award`.`remote_image`, `metaward_award`.`image`, `metaward_award`.`parent_award_id`, `metaward_award`.`slug`, `metaward_award`.`points`, T3.`id`, T3.`modified`, T3.`created`, T3.`string_id`, T3.`owner_id`, T3.`name`, T3.`description`, T3.`owner_points`, T3.`url`, T3.`remote_image`, T3.`image`, T3.`parent_award_id`, T3.`slug`, T3.`points` FROM `metaward_award` LEFT OUTER JOIN `metaward_award` T3 ON (`metaward_award`.`parent_award_id` = T3.`id`) WHERE (`metaward_award`.`owner_id` = 1135 AND `metaward_award`.`owner_points` = 20 AND `metaward_award`.`name` = 'Marksman: Campaign' AND `metaward_award`.`parent_award_id` = 27034 AND `metaward_award`.`description` = 'Kill 4 enemies with one clip of a sniper rifle.') ORDER BY `metaward_award`.`modified` DESC | 
| 480580 | paul | localhost | paul | Query | 88 | Locked  | SELECT `metaward_award`.`id`, `metaward_award`.`modified`, `metaward_award`.`created`, `metaward_award`.`string_id`, `metaward_award`.`owner_id`, `metaward_award`.`name`, `metaward_award`.`description`, `metaward_award`.`owner_points`, `metaward_award`.`url`, `metaward_award`.`remote_image`, `metaward_award`.`image`, `metaward_award`.`parent_award_id`, `metaward_award`.`slug`, `metaward_award`.`points`, T3.`id`, T3.`modified`, T3.`created`, T3.`string_id`, T3.`owner_id`, T3.`name`, T3.`description`, T3.`owner_points`, T3.`url`, T3.`remote_image`, T3.`image`, T3.`parent_award_id`, T3.`slug`, T3.`points` FROM `metaward_award` LEFT OUTER JOIN `metaward_award` T3 ON (`metaward_award`.`parent_award_id` = T3.`id`) WHERE (`metaward_award`.`owner_id` = 1135 AND `metaward_award`.`owner_points` = 5 AND `metaward_award`.`name` = 'Headshot Honcho' AND `metaward_award`.`parent_award_id` = 101442 AND `metaward_award`.`description` = 'Kill 10 enemies with headshots in a ranked free for all playlist or in campaign.') ORDER BY `metaward_award`.`modified` DESC | 
| 480581 | paul | localhost | paul | Query | 86 | Locked  | SELECT `metaward_alias`.`id`, `metaward_alias`.`modified`, `metaward_alias`.`created`, `metaward_alias`.`string_id`, `metaward_alias`.`shortname`, `metaward_alias`.`remote_image`, `metaward_alias`.`image`, `metaward_alias`.`user_id`, `metaward_alias`.`type_id`, `metaward_alias`.`md5` FROM `metaward_alias` WHERE `metaward_alias`.`string_id` = 'http://www.wowarmory.com/character-sheet.xml?r=Aegwynn&cn=Fantazamor' ORDER BY `metaward_alias`.`modified` DESC                                                                                                                                              | 
| 480626 | paul | localhost | paul | Query | 88 | Sending data | SELECT COUNT(*) FROM `metaward_alias` INNER JOIN `metaward_achiever` ON (`metaward_alias`.`id` = `metaward_achiever`.`alias_id`) INNER JOIN `metaward_award` ON (`metaward_achiever`.`award_id` = `metaward_award`.`id`) WHERE `metaward_award`.`owner_id` = 9                                                                                                                                                                                                 | 
| 480630 | paul | localhost | paul | Query | 71 | Locked  | SELECT `metaward_alias`.`id`, `metaward_alias`.`modified`, `metaward_alias`.`created`, `metaward_alias`.`string_id`, `metaward_alias`.`shortname`, `metaward_alias`.`remote_image`, `metaward_alias`.`image`, `metaward_alias`.`user_id`, `metaward_alias`.`type_id`, `metaward_alias`.`md5`, T2.`id`, T2.`modified`, T2.`created`, T2.`string_id`, T2.`shortname`, T2.`remote_image`, T2.`image`, T2.`user_id`, T2.`type_id`, T2.`md5`, T3.`id`, T3.`modified`, T3.`created`, T3.`string_id`, T3.`shortname`, T3.`remote_image`, T3.`image`, T3.`user_id`, T3.`type_id`, T3.`md5`, T4.`id`, T4.`modified`, T4.`created`, T4.`string_id`, T4.`shortname`, T4.`remote_image`, T4.`image`, T4.`user_id`, T4.`type_id`, T4.`md5`, T5.`id`, T5.`modified`, T5.`created`, T5.`string_id`, T5.`shortname`, T5.`remote_image`, T5.`image`, T5.`user_id`, T5.`type_id`, T5.`md5`, T6.`id`, T6.`modified`, T6.`created`, T6.`string_id`, T6.`shortname`, T6.`remote_image`, T6.`image`, T6.`user_id`, T6.`type_id`, T6.`md5` FROM `metaward_alias` INNER JOIN `metaward_alias` T2 ON (`metaward_alias`.`type_id` = T2.`id`) INNER JOIN `metaward_alias` T3 ON (T2.`type_id` = T3.`id`) INNER JOIN `metaward_alias` T4 ON (T3.`type_id` = T4.`id`) INNER JOIN `metaward_alias` T5 ON (T4.`type_id` = T5.`id`) INNER JOIN `metaward_alias` T6 ON (T5.`type_id` = T6.`id`) WHERE `metaward_alias`.`string_id` = 'http://kongregate.com/accounts/SrGato' ORDER BY `metaward_alias`.`modified` DESC | 
| 480632 | paul | localhost | paul | Query | 0 | NULL   | show full processlist                                                                                                                                                                                                                                                           | 
+--------+------+-----------+------+---------+------+--------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 
15 rows in set (0.00 sec) 

मैं समझ सकता अपडेट बंद होने, लेकिन क्यों का चयन करता है भी लॉक कर रहे हैं?

Answer 1

सभी चयन लॉक हुए हैं क्योंकि, अपने अद्यतन समाप्त करने के लिए इंतजार कर रहे हैं, भले ही अद्यतन अभी तक

नहीं चल रहा है मैं आपके प्रश्नों था के आदेश लगता है:

1. COUNT का चयन करें (*) से ...
2. अद्यतन metaward_award ...
3. चयन metaward_alias ...
4. ...

QUERY1 निष्पादित हो रहा है .. यह लंबे समय

QUERY2 आता है लेता है, एक लिखने ताला प्राप्त करना चाहते हैं, लेकिन नहीं कर सकते, पढ़ने है क्योंकि, तो यह इंतजार कर रहा है और संकेत यह लॉक करने के लिए

इंतज़ार कर रहा है query3 आता है, पढ़ना चाहता है लेकिन cant, क्योंकि query2 पहले से ही लॉक

अब आप कहेंगे .. MyISAM समवर्ती पढ़ता है, query3 पढ़ना चाहिए जबकि क्वेरी 1 पढ़ रहा है .. लेकिन अगर ऐसा होता, और क्वेरी 3 लंबे समय तक लेता है समय भी, आप क्वेरी 2 पर "भुखमरी" बना सकते हैं, जिसका अर्थ है कि यह कभी नहीं होगा एट निष्पादित करता है, तो QUERY1 & QUERY3 काफी समय लगा और एक दूसरे को, उदाहरण के बाद जाना:

QUERY1 संभालने, QUERY3 exec को

second | action 
1 | query1 starting 
2 | query2 cant start, waiting 
3 | query3 starting 
4 | 
5 | 
6 | qurey1 finished (query2 cant start because query3 is still reading) 
7 | another call for query1 starting 
8 | qurey3 finished (query2 cant start because the new query1 is still reading) 

Answer 2

5 सेकेंड लगते हैं आप --कम-प्राथमिकता सर्वर विकल्प का उपयोग कर सकते हैं टेबल संशोधन संचालन (INSERT, स्थान, हटाएं और अद्यतन) पर चयन विवरण प्राथमिकता देने के लिए अद्यतन

आप अपने कथन के बाद LOW_PRIORITY संशोधक का भी उपयोग कर सकते हैं (उदा। अद्यतन LOW_PRIORITY)

संपादित करें: वहाँ अधिक जानकारी यहाँ है: http://dev.mysql.com/doc/refman/5.0/en/table-locking.html