Re: pgsql: Allow numeric scale to be negative or greater than precision.

This is for migration?

Or does it mean very small values now occupy less space since we store
fewer zeros?

Thanks

On Mon, 26 Jul 2021 at 14:17, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> wrote:
>
> Allow numeric scale to be negative or greater than precision.
>
> Formerly, when specifying NUMERIC(precision, scale), the scale had to
> be in the range [0, precision], which was per SQL spec. This commit
> extends the range of allowed scales to [-1000, 1000], independent of
> the precision (whose valid range remains [1, 1000]).
>
> A negative scale implies rounding before the decimal point. For
> example, a column might be declared with a scale of -3 to round values
> to the nearest thousand. Note that the display scale remains
> non-negative, so in this case the display scale will be zero, and all
> digits before the decimal point will be displayed.
>
> A scale greater than the precision supports fractional values with
> zeros immediately after the decimal point.
>
> Take the opportunity to tidy up the code that packs, unpacks and
> validates the contents of a typmod integer, encapsulating it in a
> small set of new inline functions.
>
> Bump the catversion because the allowed contents of atttypmod have
> changed for numeric columns. This isn't a change that requires a
> re-initdb, but negative scale values in the typmod would confuse old
> backends.
>
> Dean Rasheed, with additional improvements by Tom Lane. Reviewed by
> Tom Lane.
>
> Discussion: https://postgr.es/m/CAEZATCWdNLgpKihmURF8nfofP0RFtAKJ7ktY6GcZOPnMfUoRqA@mail.gmail.com
>
> Branch
> ------
> master
>
> Details
> -------
> https://git.postgresql.org/pg/commitdiff/085f931f52494e1f304e35571924efa6fcdc2b44
>
> Modified Files
> --------------
> doc/src/sgml/datatype.sgml | 48 ++++++++++-
> src/backend/utils/adt/numeric.c | 130 +++++++++++++++++++++--------
> src/include/catalog/catversion.h | 2 +-
> src/include/utils/numeric.h | 16 +++-
> src/test/regress/expected/numeric.out | 63 ++++++++++++++
> src/test/regress/expected/sanity_check.out | 1 +
> src/test/regress/sql/numeric.sql | 34 ++++++++
> 7 files changed, 251 insertions(+), 43 deletions(-)
>

--
Simon Riggs http://www.EnterpriseDB.com/