Thom Brown wrote: > The reason I ask is because the documentation says "If character varying is > used without length specifier, the type accepts strings of any size. The > latter is a PostgreSQL extension." I wasn't sure if such an extension meant > there was a level of over-head involved, or reduced its indexability.
No - some other DBs might have different implementations (and so restrictions) but varchar and text are basically interchangeable. They are different types though, so if you add custom casts you might want to do it for both.
There is a limit on btree index size - about 2000 chars if I remember correctly. That's because you need to fit three index values on an 8KB page iirc (and there are overheads too).