Function can_expr_be_pushed_down_with_schemas 

pub fn can_expr_be_pushed_down_with_schemas(
    expr: &Arc<dyn PhysicalExpr>,
    file_schema: &Schema,
) -> bool

Recurses through expr as a tree, finds all columns, and checks if any of them would prevent this expression from being predicate pushed down. If any of them would, this returns false. Otherwise, true. Note that the schema passed in here is not the physical file schema (as it is not available at that point in time); it is the schema of the table that this expression is being evaluated against minus any projected columns and partition columns.