Bruce Momjian <pgman@candle.pha.pa.us> writes:
> OK, code backed out. If the storage formats are the same, doesn't that
> make them binary compatibile.
No, because one allows nulls and the other doesn't. If you disregard
what are legal values and what aren't, then every pair of varlena
datatypes we have could be called "binary compatible".
More to the point, though, why *should* they be marked binary
compatible? I saw no compelling reason advanced for it, and I can see a
couple of compelling reasons not to. Every binary-compatible pairing is
another hole in our type system, another opportunity for unexpected
behavior. We shouldn't add them on whims. Especially we shouldn't add
them for datatypes that aren't even of the same family. bytea isn't for
storage of textual data, and so it makes little sense to allow
application of textual operations to it.
regards, tom lane