Function eliminate_join_marks 

pub fn eliminate_join_marks(expr: Expression) -> Result<Expression>

Eliminate Oracle-style (+) join marks by converting to standard JOINs.

Oracle uses (+) syntax for outer joins:

SELECT * FROM a, b WHERE a.x = b.x(+)

This is converted to standard LEFT OUTER JOIN:

SELECT * FROM a LEFT OUTER JOIN b ON a.x = b.x

Reference: transforms.py:828-945