Re: numeric hierarchy again (was Re: floor function in 7.3b2)

Tom Lane wrote:
> Moving to the left requires an explicit cast (or at least an assignment
> to a column). I know this looks strange to someone who knows that our
> numeric type beats float4/float8 on both range and precision, but it's
> effectively mandated by the SQL spec. Any combination of "exact" and
> "inexact" numeric types is supposed to yield an "inexact" result per
> spec, thus numeric + float8 yields float8 not numeric. Another reason
> for doing it this way is that a numeric literal like "123.456" can be
> initially typed as numeric, and later implicitly promoted to float4 or
> float8 if context demands it. Doing that the other way 'round would
> introduce problems with precision loss. We had speculated about
> introducing an "unknown_numeric" pseudo-type to avoid that problem, but
> the above hierarchy eliminates the need for "unknown_numeric". We can
> initially type a literal as the smallest thing it will fit in, and then
> do implicit promotion as needed. (7.3 is not all the way there on that
> plan, but 7.4 will be.)

Do we know that defaulting floating constants will not be a performance
hit?

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