Will Pugh <willpugh(at)gmail(dot)com> writes:
> It seems that is 9.1, numerics that don't have a specified precision
> and scale are arbitrary scale/precision.
> For many operations this is straightforward. However, when doing a
> division operation that does not terminate, I'm curious about how the
> number of digits is determined.
According to select_div_scale() in src/backend/utils/adt/numeric.c,
* The result scale of a division isn't specified in any SQL standard. For
* PostgreSQL we select a result scale that will give at least
* NUMERIC_MIN_SIG_DIGITS significant digits, so that numeric gives a
* result no less accurate than float8; but use a scale not less than
* either input's display scale.
I wouldn't necessarily claim that that couldn't be improved on,
but that's what it does now.
regards, tom lane
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