Apologize but I really don't have much information for the question.
I have a single MySQL MySIAM engine table that's holding around 80K records (continually increase).
Today it's suddenly stop responding.
I can't even do a single query (e.g. SELECT * FROM table LIMIT 1), the server just spend time executing and look like will never stop.
I can't dump table to make backup.
However, another tables in the same database, same engine (MySIAM) are working just fine.
I'm not sure where to go from here. Not sure if it's DEADLOCK or anything.
All data in that table is really important. You direction pointing to help me identify the problem would be really appreciated. For example, are there any command to check table if it's corrupt by what reasons, etc.
UPDATE:::::
I can't use CHECK TABLE neither, it also take forever execution time.
UPDATE ::::
I did research and come up with something about REPAIR TABLE.
However, it's suggested that I should do the backup first.
As I can't do the back for this table, would it be OK to use the REPAIR command anyway?
::::::::::::: SOLVED :::::::::::
Follow Cristian's help, use SHOW PROCESSLIST; command. I see that there is a process with state 'Copying to tmp table' that hold another process.
So I use KILL <process id> to kill that process and everything released to normal.
Cheers
Chanon
Sorry but I can't comment your question... :)
Exactly which version of MySQL you run, 5.1.xx?
Can you post you SHOW PROCESSLIST; status?
UPDATE: Chanon, after this event, and to prevent this problem, you have to review and optimize the query that send MySQL in "Copying to tmp table" state, in order to avoid slowness and a risk of "disk full" for your temporary partition.
I used a loop in my php script to run insert queries into my db. The loop was looping thousand times. I stop my php script while it was till running. Nevertheless, my db table keeps on getting populated continously. I guess that there must be a queue. but this is only a guess. So I am wondering if I can stop all the pending queries from being executed? Also I am wondering if it is possible to see that queue somewhere? Thank you in advance for your replies. Cheers. Marc.
There is no queue, unless you were using INSERT DELAYED.
You can kill the process that is inserting the data like this:
Run SHOW PROCESSLIST to find the id of the connecton you want to kill
Then run KILL CONNECTION <thread_id> to kill that connection.
SHOW PROCESSLIST will give you a list of all currently running queries
Recently, I noticed that my MySQL server processes a lot of INSERT's. How can I detect user or DB on which is this activivty??
insert 33 k 97.96 k 44.21%
SHOW FULL PROCESSLIST will return every connection, user, and query currently active, if you have the PROCESS permission. That's more for immediate problems, but it has the least overhead.
If you use query logging, then instead of the regular query log (it can slow your server down noticeably) use the binary log to keep it minimal. It only tracks actions that change tables, like CREATE/DROP/ALTER and INSERT/UPDATE/REPLACE.
What you should log periodically (once a minute):
SHOW FULL PROCESSLIST;
SHOW GLOBAL STATUS;
with slow log enabled this will give you huge chance that any question can be solved.
If you have binary logging enabled you can check time/user who inserted rows.
If you have general log enabled then everything is logged.
Look in your query logs. This will show every connect into MySQL, and show every command that they execute.
From a script I sent a query like this thousands of times to my local database:
update some_table set some_column = some_value
I forgot to add the where part, so the same column was set to the same a value for all the rows in the table and this was done thousands of times and the column was indexed, so the corresponding index was probably updated too lots of times.
I noticed something was wrong, because it took too long, so I killed the script. I even rebooted my computer since then, but something stuck in the table, because simple queries take a very long time to run and when I try dropping the relevant index it fails with this message:
Lock wait timeout exceeded; try restarting transaction
It's an innodb table, so stuck the transaction is probably implicit. How can I fix this table and remove the stuck transaction from it?
I had a similar problem and solved it by checking the threads that are running.
To see the running threads use the following command in mysql command line interface:
SHOW PROCESSLIST;
It can also be sent from phpMyAdmin if you don't have access to mysql command line interface.
This will display a list of threads with corresponding ids and execution time, so you can KILL the threads that are taking too much time to execute.
In phpMyAdmin you will have a button for stopping threads by using KILL, if you are using command line interface just use the KILL command followed by the thread id, like in the following example:
KILL 115;
This will terminate the connection for the corresponding thread.
You can check the currently running transactions with
SELECT * FROM `information_schema`.`innodb_trx` ORDER BY `trx_started`
Your transaction should be one of the first, because it's the oldest in the list. Now just take the value from trx_mysql_thread_id and send it the KILL command:
KILL 1234;
If you're unsure which transaction is yours, repeat the first query very often and see which transactions persist.
Check InnoDB status for locks
SHOW ENGINE InnoDB STATUS;
Check MySQL open tables
SHOW OPEN TABLES WHERE In_use > 0;
Check pending InnoDB transactions
SELECT * FROM `information_schema`.`innodb_trx` ORDER BY `trx_started`;
Check lock dependency - what blocks what
SELECT * FROM `information_schema`.`innodb_locks`;
After investigating the results above, you should be able to see what is locking what.
The root cause of the issue might be in your code too - please check the related functions especially for annotations if you use JPA like Hibernate.
For example, as described here, the misuse of the following annotation might cause locks in the database:
#Transactional(propagation = Propagation.REQUIRES_NEW)
This started happening to me when my database size grew and I was doing a lot of transactions on it.
Truth is there is probably some way to optimize either your queries or your DB but try these 2 queries for a work around fix.
Run this:
SET GLOBAL innodb_lock_wait_timeout = 5000;
And then this:
SET innodb_lock_wait_timeout = 5000;
When you establish a connection for a transaction, you acquire a lock before performing the transaction. If not able to acquire the lock, then you try for sometime. If lock is still not obtainable, then lock wait time exceeded error is thrown. Why you will not able to acquire a lock is that you are not closing the connection. So, when you are trying to get a lock second time, you will not be able to acquire the lock as your previous connection is still unclosed and holding the lock.
Solution: close the connection or setAutoCommit(true) (according to your design) to release the lock.
Restart MySQL, it works fine.
BUT beware that if such a query is stuck, there is a problem somewhere :
in your query (misplaced char, cartesian product, ...)
very numerous records to edit
complex joins or tests (MD5, substrings, LIKE %...%, etc.)
data structure problem
foreign key model (chain/loop locking)
misindexed data
As #syedrakib said, it works but this is no long-living solution for production.
Beware : doing the restart can affect your data with inconsistent state.
Also, you can check how MySQL handles your query with the EXPLAIN keyword and see if something is possible there to speed up the query (indexes, complex tests,...).
Goto processes in mysql.
So can see there is task still working.
Kill the particular process or wait until process complete.
I ran into the same problem with an "update"-statement. My solution was simply to run through the operations available in phpMyAdmin for the table. I optimized, flushed and defragmented the table (not in that order). No need to drop the table and restore it from backup for me. :)
I had the same issue. I think it was a deadlock issue with SQL. You can just force close the SQL process from Task Manager. If that didn't fix it, just restart your computer. You don't need to drop the table and reload the data.
I had this problem when trying to delete a certain group of records (using MS Access 2007 with an ODBC connection to MySQL on a web server). Typically I would delete certain records from MySQL then replace with updated records (cascade delete several related records, this streamlines deleting all related records for a single record deletion).
I tried to run through the operations available in phpMyAdmin for the table (optimize,flush, etc), but I was getting a need permission to RELOAD error when I tried to flush. Since my database is on a web server, I couldn't restart the database. Restoring from a backup was not an option.
I tried running delete query for this group of records on the cPanel mySQL access on the web. Got same error message.
My solution: I used Sun's (Oracle's) free MySQL Query Browser (that I previously installed on my computer) and ran the delete query there. It worked right away, Problem solved. I was then able to once again perform the function using the Access script using the ODBC Access to MySQL connection.
Issue in my case: Some updates were made to some rows within a transaction and before the transaction was committed, in another place, the same rows were being updated outside this transaction. Ensuring that all the updates to the rows are made within the same transaction resolved my issue.
issue resolved in my case by changing delete to truncate
issue-
query:
delete from Survey1.sr_survey_generic_details
mycursor.execute(query)
fix-
query:
truncate table Survey1.sr_survey_generic_details
mycursor.execute(query)
This happened to me when I was accessing the database from multiple platforms, for example from dbeaver and control panels. At some point dbeaver got stuck and therefore the other panels couldn't process additional information. The solution is to reboot all access points to the database. close them all and restart.
Fixed it.
Make sure you doesn't have mismatched data type insert in query.
I had an issue where i was trying "user browser agent data" in VARCHAR(255) and having issue with this lock however when I changed it to TEXT(255) it fixed it.
So most likely it is a mismatch of data type.
I solved the problem by dropping the table and restoring it from backup.
I have some strange bug into a application(or is it the MySQL build?) that causes queries to remain in "locked" state forever, filling up the max number of threads.
I read about setting the wait_timeout variable to kill the "bogus" threads after a period of time. This works ok, but I would like to log the killed queries for further inspection/making sure backup scripts are not killed.
Is there any possibility to do that?
Thanks.
You might be able to use the slow log, but I'm not sure if the problem is that they never complete. Worth a shot.
Also, you may be able to see what's going on by running SHOW FULL PROCESSLIST while you've got dead threads. It should show you what the problem is and what the query was.
If you can simulate this in a development environment, you could also turn on general query logging (which records every statement) and then just tail the log after it crashes.
In the past, I have tagged queries with a unique comment (per query type):
/* Query_12345 */ SELECT ... FROM ... WHERE ... LIMIT ...
A background process would poll SHOW FULL PROCESSLIST and look for any queries that were more than X seconds long, and tagged with Query_NNNNN.
Finally, it would kill them if they went on too long. This allowed the server to breath while we figured out how to optimize the 80,000,000 record table that was slowing things down.