Support generative functions like pivot or lateral view explode

[collerek]

Thread to discuss if we should support generative functions like pivot or lateral view explode

You cannot create a discussion from issue (only other way around), so below orginal comments from #161

collerek:
I need your opinion on this, we do not support lateral view explode keyword as of now, the question is if we should?

https://spark.apache.org/docs/latest/sql-ref-syntax-qry-select-lateral-view.html

in a part lateral view explode(impr_list) table as l :

the impr_list is now recognized as a table (and this actually is a column) #bug even after #162
table is an alias not an actual table so should NOT go into tables
in theory l is a column_alias but when you i.e. explode multiple arrays you can have multiple ones -> https://dwgeek.com/what-is-hive-lateral-view-and-how-to-use-it.html/ but they do not have to refer to actual db column
If i'm not mistaken this only refers to hive/spark sql dialect.

What should we do with this?

macbre:
Tricky one. Then comes the question if we should for instance support PIVOT as well?