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Re: info on open tables




2018/09/28 07:48 ... Machiel Richards:
       During the times when it experiences issues, I found that there is always about 4-5 processes on mysql that gets stuck on "closing table" state and once the software (opensips) is restarted due to a sigfault, then these queries are killed as well.


       Based on information found we added grafana graphs and did notice that the table_open_cache is fully used during the time of the sigfaults and the queries getting stuck so we tested by increasing the table_open_cache.


      This did however not resolve the issue as we simply saw table_open_cache using the full value of 3000 and once again the same behaviour.



      When running "Show open tables" though, we find that the amount of open tables is only 283 and a count of all tables returned that there is only 381 tables on the server.


     However when running "Show global status like 'open_tables' we get a value of 2900.


     So my questions are as follows :


      1. Why is the table_open_cache used up if there are not even that many tables.

      2. Why does these values differ so much? or do they provide different info.


These occur to me:

"If you have no privileges for a table, it does not show up in the output from SHOW OPEN TABLES."

If an table is kept open, but there is no action, does it stay in the cache?

One shows really only the tables, the other shows a table with its user.

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