Function analyze_join_sides 

pub fn analyze_join_sides(left: &SqlPlan, right: &SqlPlan) -> BitmapJoinHints

Analyze both join children and return bitmap-pushdown hints.

Neither side is penalized for being analyzed — if both qualify, both hints are emitted so the executor can inject prefilters on both probe scans. This is safe: the executor will only use the bitmap that matches the collection it is about to scan.