pgsql: Clarify the choice of rscale in numeric_sqrt().

Clarify the choice of rscale in numeric_sqrt().

Improve the comment explaining the choice of rscale in numeric_sqrt(),
and ensure that the code works consistently when other values of
NBASE/DEC_DIGITS are used.

Note that, in practice, we always expect DEC_DIGITS == 4, and this
does not change the computation in that case.

Joel Jacobson and Dean Rasheed

Discussion: https://postgr.es/m/06712c29-98e9-43b3-98da-f234d81c6e49%40app.fastmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/0736fc1ceb0659a9f73699910ac56603336daeee

Modified Files
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src/backend/utils/adt/numeric.c | 17 +++++++++++++++--
1 file changed, 15 insertions(+), 2 deletions(-)