[TYPO3-mvc] Using a mapping tables

[Marcus Budzyn]

Extbase, TYPO3 V6.2

History: http://forum.typo3.org/index.php/t/206813/

A field of an entity that contains a 3 letter code (e. g. "E02"). should be mapped to its verbose description (e. g. "Catalan").
My first (naive) approach was using a partial to map these 500 values, which sadly ran into an out of memory error.

My question is: 
What is the best way to accomplish this? What about using a regular 1:n relation, having the 3 letter code as the primary key? But it seems that ExtBase relations (built by the ExtensionBuilder) use integers only (for the keys)?

Any hints would be greatly appreciated!

Marcus