yesodweb/persistent — comment on commit e88300b42c489019131c3ae26333db218f6317b9
File: persistent/Database/Persist/Store.hs line 375
By gregwebs:

Originally I was thinking that the SQL backend would convert a PersistMap/PersistList into JSON.
That has an advantage of keeping the aeson dependency in SQL (even if we aren't breaking out dependencies now).
However, that would require a way for SQL to keep track of the real type of the string.
I haven't actually used this feature, but I do know that many SQL engines support the creation of types.
The other approach would be for fromPersistValue to use extra information (sqlType perhaps).
Just an idea.

Storing a String seems very convenient. There is another work-around used by Show and some others for dealing with lists. Is it possible for Persistent to automatically pack a String to a Text somehow before we reach this point?