Function unnest_subqueries 

pub fn unnest_subqueries(expression: Expression) -> Expression

Unnest correlated subqueries where possible.

This transforms correlated subqueries into JOINs for better performance.

Example

-- Before:
SELECT * FROM x WHERE x.a IN (SELECT y.a FROM y WHERE x.b = y.b)
-- After:
SELECT * FROM x LEFT JOIN y ON x.b = y.b WHERE x.a = y.a

Arguments

• expression - The expression to optimize

Returns

The optimized expression with unnested subqueries