255 character keys in tables

[JohnDBarrett]

Many tables have 255 character ID fields used as indexes and keys. In some character sets, one character can translate to up to 4 bytes. This is compounded in some tables (PRODUCT_CAT for example) where multiple IDs are used to create a unique key.

The storage and processing overhead of this is very significant and optimisation is needed.

This can effect some MySQL installations using the MyISAM engine. The CREATE TABLE instruction can fail with the message "Specified key was too long; max key length is 1000". The solution to this is to change the default DB engine to innoDB.