pgsql-bugs(at)postgresql(dot)org writes:
> real or float4 '=' operator is broken in 7.1.2
No, it isn't --- try coercing the values you are comparing against
to be float4. Your error is in assuming that 29.92::float8 should
equal 29.92::float4 coerced back to float8. Which might be a nice
property to have, but it's not the real behavior of real floating-
point arithmetics.
regards, tom lane