detecting locked tables mysql (locked by LOCK TABLE)

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 8,31832755

asked Mar 23 '10 at 12:55 Marcin 2,18452553

Why don't you unlock the table first ? –  David V. Mar 23 '10 at 13:07

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@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 905719

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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 203k16128227

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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 578314

answered Aug 25 '12 at 7:10 Aruman 39638

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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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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 Giles Smith 1087

this only works for named locks what about non named locks? –  Marcin Apr 5 '10 at 12:32

You can't for non named locks –  Giles Smith Apr 6 '10 at 16:31

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This article describes how to get information about locked MySQL resources. mysqladmin debugmight also be of some use.

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edited Mar 23 '10 at 13:12

answered Mar 23 '10 at 13:06 Tomislav Nakic-Alfirevic 5,76211735

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its fine but what about MyISAM being locked ? cheers –  Marcin Mar 23 '10 at 13:56

Sorry, can't help you there. –  Tomislav Nakic-Alfirevic Mar 23 '10 at 15:02

http://stackoverflow.com/questions/2499976/detecting-locked-tables-mysql-locked-by-lock-table