Thread: double precisoin type
Hello,
postgres [1264904]=# select 123456789.123456789123456::double precision;
┌────────────────────┐
│ float8 │
├────────────────────┤
│ 123456789.12345679 │
└────────────────────┘
(1 row)
I do not understand why this number is truncated at 123456789.12345679 that is 17 digits and not 15 digits
Any idea
Fabrice
Documentation says:
double precision | 8 bytes | variable-precision, inexact | 15 decimal digits precision |
Fabrice Chapuis <fabrice636861@gmail.com> writes:
> Documentation says:
> double precision 8 bytes variable-precision, inexact 15 decimal digits
> precision
The documentation is stating the minimum number of decimal digits
that will be accurately reproduced. You got 16 reproduced correctly
in this example, but you were lucky.
float8out has a different rule, which is to emit enough digits to
describe the actually-stored binary value unambiguously, so that
dump and reload will not change the stored value.
regards, tom lane