Build Exprs for all columns with a list of filter conditions.
For example, consider you have a partitioned table for three columns (i.e., col1, col2, col3).
Then, this methods will create three Exprs for (col1), (col2), (col3).
Assume that an user gives a condition WHERE col1 ='A' and col3 = 'C'.
There is no filter condition corresponding to col2.
Then, the path filter conditions are corresponding to the followings:
The first Expr: col1 = 'A'
The second Expr: col2 IS NOT NULL
The third Expr: col3 = 'C'
'IS NOT NULL' predicate is always true against the partition path.