> surely, it's not just a case of float4 display, type casting seems to be affected, too.
I have run some more tests and I'd like to take this back. The reason our equality tests fail when extra_float_digits = 2 is this: we are constructing dynamic SQL statements inside a PL/pgSQL function. The SQL produced is, of course, affected by the textual representation of REALs in effect, hence the problems we have encountered. Thanks, this is making much more sense now.