Wrong table cache hit rate calculation

[MichaIng]

Based on https://github.com/major/MySQLTuner-perl/blob/master/mysqltuner.pl#L2706 the table cache hit rate is currently calculated as ratio of Open_tables and Opened_Tables, hence the currently opened non-temporary tables and the overall opened tables. But this does not represent that cache hit rate where the table_open_cache recommended should be based on, does it?

There are two stats for table cache hits and misses which seem to be the correct ones here:

MariaDB [(none)]> show global status like 'Table_open_cache_%';
+-----------------------------------+----------+
| Variable_name                     | Value    |
+-----------------------------------+----------+
| Table_open_cache_active_instances | 1        |
| Table_open_cache_hits             | 22555304 |
| Table_open_cache_misses           | 2866     |
| Table_open_cache_overflows        | 0        |
+-----------------------------------+----------+

=>

int( $mystat{'Table_open_cache_hits'} * 100 / ( $mystat{'Table_open_cache_hits'} + $mystat{'Table_open_cache_misses'} ) );

[MichaIng]

Many thanks for 2079639, it works as expected here now.

Btw, I just verified that these variables are the same on MySQL, but they have been introduced with v5.6: https://dev.mysql.com/doc/refman/5.6/en/added-deprecated-removed.html

[sbrowne-godaddy]

Whilst a little late, this now breaks the math if Table_open_cache_hits or Table_open_cache_misses isn't present in the hash. The items the math depends upon are no longer having their existence tested.