Optimize on FromDual GmbH

To NULL, or not to NULL, that is the question!

oli.sennhauser@fromdual.com (Oli Sennhauser) — Fri, 14 Dec 2018 08:33:25 +0000

As we already stated in earlier articles in this blog
[1 and 2
] it is a good idea to use NULL values properly in MariaDB and MySQL.

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 much space does NULL need?

oli.sennhauser@fromdual.com (Oli Sennhauser) — Sun, 08 Feb 2026 16:15:00 +0100

The last time I consulted a customer, he came up to me beaming with joy and said that he had taken my advice and changed all the primary key columns from BIGINT (8 bytes) to INT (4 bytes) and that had made a big difference! His MySQL 8.4 database is now 750 Gbyte smaller (from 5.5 Tbyte). Nice!