It is good to see that obviously Oracle has since then improved some of these and added new ones as well.
Here are some links to the corresponding posts:
New automatic Parallel Outer Join Null Handling in 18c
Improvements regarding automatic parallel distribution skew handling in 18c
Chinar has also put some more thoughts on the HASH JOIN BUFFERED operation:
There are also a number of posts on his blog regarding histograms and in particular how to properly calculate the join cardinality in the presence of additional filters and resulting skew, which is a very interesting topic and yet to be handled properly by the optimizer even in the latest versions.
