I'm betting that's coming from scalargtsel, which doesn't know anything about your type, but you've nominated it to be the selectivity function for ">" anyway.
/* * Can't get here unless someone tries to use scalarltsel/scalargtsel on * an operator with one numeric and one non-numeric operand. */ elog(ERROR, "unsupported type: %u", typid);
regards, tom lane
Yes, I found it in the code, but I followed the example from the postgres documentation that uses this function.
And why does it work sometimes? Why not other times?