detecting locked tables mysql (locked by LOCK TABLE)

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I would like to know whether there is an option to detect locked tables in mysql or not. I mean locked by LOCK TABLE table WRITE/READ command?

mysql locking

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edited Aug 26 ‘12 at 1:36

pero
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asked Mar 23 ‘10 at 12:55

Marcin
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Why don‘t you unlock the table first ? – David V. Mar 23 ‘10 at 13:07

@David V.: I guess because he needs to know it is locked first? Or maybe he want‘s to avoid ‘touching‘ the table when/if it is locked? – lexu Mar 23 ‘10 at 13:11

O_O Ooooh my bad, I read that as "delete" (and deleting in the title) locked tables. – David V. Mar 23 ‘10 at 13:42

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5 Answers

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You can‘t for non-named locks!

More info: http://forums.mysql.com/read.php?21,222363,223774#msg-223774

Not unless you use an advisory lock first. You might also want to look into using INSERT DELAYED instead.

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edited Sep 15 at 9:32

answered Apr 5 ‘10 at 18:48

confiq
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up vote29down vote

You can use SHOW OPEN TABLES to show each table‘s lock status. More details on the command‘s doc page are here.

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answered Apr 5 ‘10 at 18:41

Marc B
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Use SHOW OPEN TABLES: http://dev.mysql.com/doc/refman/5.1/en/show-open-tables.html

You can do something like this

SHOW OPEN TABLES WHERE `Table` LIKE ‘%foo%‘ AND Database LIKE ‘[DBNAME]‘ AND In_use > 0;

to check any locked tables in a database.

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edited Oct 25 ‘13 at 12:07

borrel
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answered Aug 25 ‘12 at 7:10

Aruman
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Note: I can only get this query to work if I use `Database` instead of just Database – rinogo Feb 11 at 23:06

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up vote3down vote

You can create your own lock with GET_LOCK(lockName,timeOut)

If you do a GET_LOCK(lockName, 0) with a 0 time out before you lock the tables and then follow that with a RELEASE_LOCK(lockName) then all other threads performing a GET_LOCK() will get a value of 0 which will tell them that the lock is being held by another thread.

However this won‘t work if you don‘t have all threads calling GET_LOCK() before locking tables. The documentation for locking tables is here

Hope that helps!

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answered Mar 31 ‘10 at 11:07