Re: BUG #18390: exponentiation produces float datatype, but nth-root produces integer

"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Tuesday, March 12, 2024, PG Bug reporting form <noreply@postgresql.org>
> wrote:
>> However, an nth-root calculation from that float result does NOT produce a
>> new float result:

> The issue is you expect dividing two integers to produce a float but that
> isn’t how that works.  Dividing two integers produces an integer.  In this
> case zero, or .1 rounded down/truncated.

Possibly adding to the OP's confusion: not one of these examples
contains any float arithmetic whatsoever.  They're of type numeric.

=# select pg_typeof(2.5937424601000000^(1.0/10));
 pg_typeof
-----------
 numeric
(1 row)

See
https://www.postgresql.org/docs/current/sql-syntax-lexical.html#SQL-SYNTAX-CONSTANTS-NUMERIC
which says

    A numeric constant that contains neither a decimal point nor an
    exponent is initially presumed to be type integer if its value
    fits in type integer (32 bits); otherwise it is presumed to be
    type bigint if its value fits in type bigint (64 bits); otherwise
    it is taken to be type numeric. Constants that contain decimal
    points and/or exponents are always initially presumed to be type
    numeric.

A cast to float would occur only if the value is fed to an operator
that doesn't come in an exactly matching datatype.

            regards, tom lane