Re: About NULL's position in order by

[Julian Hyde]

> On Nov 15, 2015, at 6:50 PM, Li Yang <liy...@apache.org> wrote:
> 
> https://issues.apache.org/jira/browse/CALCITE-969

Li Yang, Thanks for logging that.

I realized that we have two issues, so I logged 
https://issues.apache.org/jira/browse/CALCITE-970 for the other part. 970 makes 
NULL values sort HIGH, by default, which is consistent with Oracle.

But it will change some SQL behavior. Currently

  ORDER BY x DESC

is equivalent to

  ORDER BY x DESC NULLS LAST

but after 970 it will be equivalent to

  ORDER BY x DESC NULLS FIRST

If you like the current behavior, you can set defaultNullCollation=LAST. Also, 
I tightened up what happens in RelNode land; we now use 
NullDirection.UNSPECIFIED a lot less than we used to.

Please holler if you don’t like 970.

Julian