Peter Eisentraut <peter_e@gmx.net> writes:
> But why is this called lossy? Shouldn't it be called "exceedy"?
Good point ;-). "lossy" does sound like the index might "lose" tuples,
which is exactly what it's not allowed to do; it must find all the
tuples that match the query.
The terminology is correct by analogy to "lossy compression" --- the
index loses information, in the sense that its result isn't quite the
result you wanted. But I can see where it'd confuse the unwary.
Perhaps we should consult the literature and see if there is another
term for this concept.
regards, tom lane