>>>>> "Bruce" == Bruce Momjian <bruce@momjian.us> writes:
>> I noticed that the compatibility note for Andrew Gierth's RYU
>> floating point patch seems to simply say why the feature is useful.
>> Shouldn't it be listed separately, and its impact on users upgrading
>> be listed here instead?
Bruce> The text is now in the incompatibility section:
Bruce> http://momjian.us/pgsql_docs/release-12.html
Bruce> Avoid performing unnecessary rounding of REAL and DOUBLE PRECISION
Bruce> values (Andrew Gierth)
Bruce> This dramatically speeds up processing of floating-point values, though
Bruce> trailing digits are display slightly differently. Users who wish to have
Bruce> ------------------------------------------------
Bruce> output that is rounded can set extra_float_digits=0.
Bruce> Do I need more?
That isn't quite how I'd have worded it, but I'm not sure what the best
wording is. Something like:
* Output REAL and DOUBLE PRECISION values in shortest-exact format by
default, and change the behavior of extra_float_digits
Previously, float values were output rounded to 6 or 15 decimals by
default, with the number of decimals adjusted by extra_float_digits.
The previous rounding behavior is no longer the default, and is now
done only if extra_float_digits is set to zero or less; if the value
is greater than zero (which it is by default), a shortest-precise
representation is output (for a substantial performance improvement).
This representation preserves the exact binary value when correctly
read back in, even though the trailing digits will usually differ
from the output generated by previous versions when
extra_float_digits=3.
But I'm not 100% happy with this wording and am entirely open to
suggestions for improvement.
(In passing I've spotted some related typos in the body of the docs
which are probably my fault, I'll fix those.)
--
Andrew (irc:RhodiumToad)
