Open Table Cache (1024 limit vs. 100 mil. opened tables)
Posted by: Kim Waldorff Østergaard
Date: February 27, 2019 09:17AM


I'm rather new to MySql but our company administrates a Azure-based Wordpress site having a MySQL @ClearDB. It is not performing well.

Started looking a various things, came to open_tables caching and suspects something is very wrong here.... Also the MySQL Workbench shows "Table Open Cache" efficiency being 0% which triggered me initially.

A few results from queries:

show global status like 'open%' -->

# Variable_name, Value
'Open_files', '249'
'Open_streams', '0'
'Open_table_definitions', '991'
'Open_tables', '1024'
'Opened_files', '353286840'
'Opened_table_definitions', '105680951'
'Opened_tables', '108351330'


# Variable_name, Value
'Uptime', '6549312'
'Uptime_since_flush_status', '6549312'

Some connection query results -->

# Variable_name, Value
Max_used_connections 146
max_connections 1000

I've watched the Opened_tables over 24 minutes, and below are results at time 0, +11m and +23m:

time count increase
15:50 108351330
16:01 108362801 11471
16:13 108375427 12626

So around 10000 increase per 10 minutes, roughly at this time a day (afternoon).

If any suggestions for quick win/optimizations, I'm all ears. Have not yet fully dived into the table cache and max connection logic.

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