On Tue, Mar 24, 2015 at 09:47:56AM -0400, Noah Misch wrote: > On Sun, Mar 22, 2015 at 10:53:12PM -0400, Bruce Momjian wrote: > > On Sun, Mar 22, 2015 at 04:41:19PM -0400, Noah Misch wrote: > > > On Wed, Mar 18, 2015 at 05:52:44PM -0400, Bruce Momjian wrote: > > > > This "junk" digit zeroing matches the Oracle behavior: > > > > > > > > SELECT to_char(1.123456789123456789123456789d, > > > > '9.9999999999999999999999999999999999999') as x from dual; > > > > ------ > > > > 1.1234567891234568000000000000000000000 > > > > > > > > Our output with the patch would be: > > > > > > > > SELECT to_char(float8 '1.123456789123456789123456789', > > > > '9.9999999999999999999999999999999999999'); > > > > ------ > > > > 1.1234567891234500000000000000000000000 > > > > These outputs show Oracle treating 17 digits as significant while > > > PostgreSQL > > > treats 15 digits as significant. Should we match Oracle in this respect > > > while > > > we're breaking compatibility anyway? I tend to think yes. > > > > Uh, I am hesistant to adjust our precision to match Oracle as I don't > > know what they are using internally. > > http://sqlfiddle.com/#!4/8b4cf/5 strongly implies 17 significant digits for > float8 and 9 digits for float4.
OK, I am fine in using those values if you can find them as compiler defines, but I don't see how we can grab those values from a user test on Oracle. There are some "invisible" float digits that don't appear in %f but can be shown if desired --- I think we used to do that in the regression tests, but found they added too much platform-specific randomness. Do we want to go in that direction? -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
