Table_definition_cache on FromDual GmbH

Linux system calls of MySQL process

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 15 Mar 2019 17:06:24 +0000

We had the problem today that a MySQL Galera Cluster node with the multi-tenancy pattern caused a lot of system time (sy 75%, load average about 30 (you really must read this article by Brendan Gregg, it is worth it!)) so we wanted to find what system calls are being used to see what could cause this issue (to verify if it is a TOC or a TDC problem:

Table definition cache too small

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 15 Jul 2015 06:08:36 +0000

The number of table definitions (SHOW CREATE TABLE<br>G) that can be stored in the table definition cache (table_definition_cache). If you have a large number of tables (
> 400) in your database instance, you should consider a larger table definition cache to increase your database throughput and decrease your query latency.
The command SELECT COUNT(*) FROM information_schema.tables; shows you how many tables and thus table definitions you have. The global status Open_table_definitions is the current amount of open table definitions.

How MySQL behaves with many schemata, tables and partitions

oli.sennhauser@fromdual.com (Oli Sennhauser) — Wed, 30 Nov 2011 15:35:28 +0000

Introduction

Recently a customer claimed that his queries were slow some times and sometimes they were fast.

Configuration of MySQL for Shared Hosting

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 22 Apr 2011 13:03:31 +0000

If you ask around about shared hosting setups with MySQL everybody is frightened. In fact it looks like shared hosting is one of the most difficult setups you can get.