我正试图围绕偶尔出现的InnoDB僵局：
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LATEST DETECTED DEADLOCK
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110511 10:45:59
*** (1) TRANSACTION:
TRANSACTION 0 959459752, ACTIVE 0 sec, process no 24148, OS thread id 2958613424 starting index read
mysql tables in use 16, locked 16
LOCK WAIT 2 lock struct(s), heap size 320
MySQL thread id 13029007, query id 85826239 localhost andrew updating
DELETE FROM `clients_permission_assignments` WHERE permission_assignment_id = 3761 AND client_id IN (52621)
*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 0 page no 1490959 n bits 864 index `unique_index` of table `test/clients_permission_assignments` trx id 0 959459752 lock_mode X waiting
Record lock, heap no 202 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
0: len 4; hex 8000cd8d; asc ;; 1: len 4; hex 80000eb1; asc ;; 2: len 6; hex 0000006b7d5c; asc k}\;;
*** (2) TRANSACTION:
TRANSACTION 0 959459751, ACTIVE 0 sec, process no 24148, OS thread id 1996331952 fetching rows, thread declared inside InnoDB 354
mysql tables in use 16, locked 16
20 lock struct(s), heap size 2496, undo log entries 1
MySQL thread id 13019094, query id 85826237 localhost andrew Copying to tmp table
CREATE TEMPORARY TABLE tmp_tests_people_cleanup_table (SELECT unit_code FROM (
SELECT u.unit_code, COUNT(u.unit_code) AS cnt FROM staging.client_test_utilization u
LEFT JOIN permission_assignments pa ON pa.person_id =
(SELECT person_id FROM permission_assignments pa WHERE pa.id = OLD.permission_assignment_id)
LEFT JOIN permissions p ON pa.permission_id = p.id
LEFT JOIN clients_permission_assignments cpa ON cpa.permission_assignment_id = pa.id
LEFT JOIN clients c ON c.id = cpa.client_id
LEFT JOIN staging.client_test_utilization u2 ON CONCAT('C',u2.client_number) = c.number
AND u2.unit_code = u.unit_code
WHERE p.label = 'Receive Test Updates'
AND CONCAT('C',u.client_number) = (SELECT number from clients WHERE id = OLD.client_id)
AND u2.id IS NULL GROUP BY u.unit_code
) tbl
WHERE cnt = (SELECT COUNT(*) FROM permission_assignments pa
LEFT JOIN permissions p ON pa.permission_id = p.id
LEFT JOIN clients_permission_assignments cpa ON cpa.permission_assignment_id = pa.id
WHERE p.label = 'Receive Test Updates' AND pa.person_id =
(SELECT person_id FROM permission_assignments pa WHERE pa.id = OLD.permission_assignment_id))
OR (SELECT COUNT(*) FROM permission_assignments pa
LEFT JOIN permissions p ON pa.permission_id = p.id
LEFT JOIN clients_permission_assignments cpa ON cpa.permission_assignment_id = pa.id
WHERE p.label = 'Receive Test Updates' AND pa.person_id =
(SELECT person_id FROM permission_assignments pa WHERE pa.id = OLD.permission_assignment_id)) = 0)
*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 0 page no 1490959 n bits 864 index `unique_index` of table `test/clients_permission_assignments` trx id 0 959459751 lock_mode X locks rec but not gap
Record lock, heap no 202 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
0: len 4; hex 8000cd8d; asc ;; 1: len 4; hex 80000eb1; asc ;; 2: len 6; hex 0000006b7d5c; asc k}\;;
*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 0 page no 1490959 n bits 864 index `unique_index` of table `test/clients_permission_assignments` trx id 0 959459751 lock mode S waiting
Record lock, heap no 202 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
0: len 4; hex 8000cd8d; asc ;; 1: len 4; hex 80000eb1; asc ;; 2: len 6; hex 0000006b7d5c; asc k}\;;
*** WE ROLL BACK TRANSACTION (1)
我当时不知道，但似乎INSERT ... SELECT，CREATE ... SELECT锁定SELECT查询中的所有表。如您所见，有很多表包含连接和子查询。我认为锁将是一个共享（S）锁，但从上面的数据来看，它似乎拥有一个独占（X）锁;我不明白为什么。
也许如果有人可以帮我解释为什么在CREATE上有一个独占（X）锁定... SELECT查询我可以尝试解决这个死锁问题。或许我可以从僵局中获得进一步的帮助。
谢谢。
答案 0 :(得分：0)
我发现独占锁不是来自CREATE ... SELECT查询，而是它之前的查询，它必须在同一个事务中。
我遗漏了一个重要的细节：CREATE ... SELECT查询是clients_permission_assignments上的AFTER DELETE触发器。我发现问题是DELETE查询在某些clients_permission_assignments记录上持有独占锁，并且在每次删除之后，CREATE ... SELECT查询尝试在已经具有独占锁的记录上获取共享锁DELETE查询。 CREATE ... SELECT查询必须等待删除所有行并释放独占锁。但是，当这个过程发生时，用户没有享受等待，所以他们再次启动了DELETE查询，这导致了死锁。
谢谢。