Enable Null Join Optimization for outer joins

Detail name	Value
Changelog Number	10710
Type	Improvement
Status	Open

Background

Exasol already uses a special optimization for inner joins with join conditions such as

--null join
select * from t1 
inner join t2 
on t1.id=t2.id or (t1.id is null and t2.id is null

This optimization was disabled for outer joins in EXASOL-2748 due to possible wrong results.

Improvement

The optimization is extended to include outer joins to improve the runtime of such queries.