[jira] [Created] (CASSANDRA-9224) Figure out a better default float precision rule for cqlsh

["Tyler Hobbs (JIRA)" <ji...@apache.org>]

Tyler Hobbs created CASSANDRA-9224:
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             Summary: Figure out a better default float precision rule for cqlsh
                 Key: CASSANDRA-9224
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9224
             Project: Cassandra
          Issue Type: Improvement
          Components: Tools
            Reporter: Tyler Hobbs
            Assignee: Stefania
             Fix For: 3.0, 2.1.5


We currently use a {{DEFAULT_FLOAT_PRECISION}} of 5 in cqlsh with formatting {{'%.*g' % (float_precision, val)}}.  In practice, this is way too low.  For example, 12345.5 will show up as 123456.  Since the float precision is used for cqlsh's COPY TO, it's particularly important that we maintain as much precision as is practical by default.

There are some other tricky considerations, though.  If the precision is too high, python will do something like this:

{noformat}
> '%.25g' % (12345.5555555555555555,)
'12345.55555555555474711582'
{noformat}

That's not terrible, but it would be nice to avoid if we can.



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