I hope the common cases is that data files do not contain these special float values. As the simplest solution, how about writers refrain from populating the stats if a special value is encountered?
That fix does not preclude a more thorough solution in the future, but it addresses the common case quickly. For existing data files we could check the writer version ignore filters on float/double. I don't know whether min/max filtering is common on float/double, but I suspect it's not. On Fri, Feb 16, 2018 at 8:38 AM, Tim Armstrong <tarmstr...@cloudera.com> wrote: > There is an extensibility mechanism with the ColumnOrder union - I think > that was meant to avoid the need to add new stat fields? > > Given that the bug was in the Parquet spec, we'll need to make a spec > change anyway, so we could add a new ColumnOrder - FloatingPointTotalOrder? > at the same time as fixing the gap in the spec. > > It could make sense to declare that the default ordering for floats/doubles > is not NaN-aware (i.e. the reader should assume that NaN was arbitrarily > ordered) and readers should either implement the required logic to handle > that correctly (I had some ideas here: > https://issues.apache.org/jira/browse/IMPALA-6527? > focusedCommentId=16366106&page=com.atlassian.jira. > plugin.system.issuetabpanels%3Acomment-tabpanel#comment-16366106) > or ignore the stats. > > On Fri, Feb 16, 2018 at 8:15 AM, Jim Apple <jbap...@cloudera.com> wrote: > > > > We could have a similar problem > > > with not finding +0.0 values because a -0.0 is written to the max_value > > > field by some component that considers them the same. > > > > My hope is that the filtering would behave sanely, since -0.0 == +0.0 > > under the real-number-inspired ordering, which is distinguished from > > total Ordering, and which is also what you get when you use the > > default C/C++ operators <, >, <=, ==, and so on. > > > > You can distinguish between -0.0 and +0.0 without using total ordering > > by taking their reciprocal: 1.0/-0.0 is -inf. There are some other > > ways to distinguish, I suspect, but that's the simplest one I recall > > at the moment. > > >
