Does Innodb have U-Lock ?

[SeWoong Jeon]

Hi , I'm using MySQL Enterprise 5.0.40.
I have some problem about Innodb deadlock.

(Trx1) UPDATE tb_sample SET cnt=cnt+1 WHERE pk=10
(Trx2) UPDATE tb_sample SET cnt=0 WHERE pk=10

Trx1 get S-Lock for read "cnt"
Trx2 request X-Lock, but wait for end of Trx1
Trx1 request X-Lock for update, but wait for end of Trx2
--> DeadLock!! Trx2 was roll-backed by Innodb

MSSQL use U-Lock to prevent such situration of deadlock in repeatable read or serializable transaction.
http://msdn.microsoft.com/en-us/library/ms175519.aspx

Doesn't Innodb have U-Lock?
If InnoDB doesn't have U-Lock, I think Trx1 have to get X-Lock first not S-Lock.
How can I solve this deadlock problem?

===================================================
this is my real deadlock message
Primary of "buddylist" table is "userid + buddyid"
===================================================

*** (1) TRANSACTION:
TRANSACTION 0 1340575717, ACTIVE 0 sec, process no 12769, OS thread id 1262823776 starting index read
mysql tables in use 1, locked 1
LOCK WAIT 2 lock struct(s), heap size 368
MySQL thread id 648655934, query id 7991043214 192.168.1.80 was updating
DELETE FROM MyDB.buddylist WHERE userid='[e-mail]' AND buddyid='[e-mail]' AND (btype='1' OR btype='2' OR btype='3')
*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 669 page no 226142 n bits 248 index `PRIMARY` of table `MyDB/buddylist` trx id 0 1340575717 lock_mode X locks rec but not gap waiting
Record lock, heap no 163 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
0: len 19; hex 726a73646c32303430406e617665722e636f6d; asc [e-mail];; 1: len 18; hex 676f766c34323037406e617665722e636f6d; asc [e-mail];; 2: len 6; hex 00004aee94ad; asc J ;; 3: len 7; hex 000000002d24b6; asc -$ ;; 4: len 1; hex 81; asc ;; 5: len 8; hex 80001243736601be; asc Csf ;;

*** (2) TRANSACTION:
TRANSACTION 0 1340575719, ACTIVE 0 sec, process no 12769, OS thread id 1297701216 starting index read, thread declared inside InnoDB 500
mysql tables in use 1, locked 1
3 lock struct(s), heap size 1216
MySQL thread id 648655935, query id 7991043224 192.168.1.79 was Updating
UPDATE MyDB.buddylist SET btype=btype|4 WHERE userid='[e-mail]' AND buddyid='[e-mail]'
*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 669 page no 226142 n bits 248 index `PRIMARY` of table `MyDB/buddylist` trx id 0 1340575719 lock mode S locks rec but not gap
Record lock, heap no 163 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
0: len 19; hex 726a73646c32303430406e617665722e636f6d; asc [e-mail];; 1: len 18; hex 676f766c34323037406e617665722e636f6d; asc [e-mail];; 2: len 6; hex 00004aee94ad; asc J ;; 3: len 7; hex 000000002d24b6; asc -$ ;; 4: len 1; hex 81; asc ;; 5: len 8; hex 80001243736601be; asc Csf ;;

*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 669 page no 226142 n bits 248 index `PRIMARY` of table `MyDB/buddylist` trx id 0 1340575719 lock_mode X locks rec but not gap waiting
Record lock, heap no 163 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
0: len 19; hex 726a73646c32303430406e617665722e636f6d; asc [e-mail];; 1: len 18; hex 676f766c34323037406e617665722e636f6d; asc [e-mail];; 2: len 6; hex 00004aee94ad; asc J ;; 3: len 7; hex 000000002d24b6; asc -$ ;; 4: len 1; hex 81; asc ;; 5: len 8; hex 80001243736601be; asc Csf ;;

*** WE ROLL BACK TRANSACTION (2)



Edited 5 time(s). Last edit at 09/23/2008 08:59AM by SeWoong Jeon.