[Question] prune_col in optimizer.optimize

[chowc]

In optimze function: required columns are determined by plan.out_types(),

risinglight/src/optimizer/mod.rs

Lines 51 to 52 in c859dff

	let out_types_num = plan.out_types().len();
	plan = plan.prune_col(BitSet::from_iter(0..out_types_num));

but in PlanNode.prune_col function, the input types are also determined by out_types() of the same plan.

Will required_cols parameter always same as input_types?

risinglight/src/optimizer/plan_nodes/mod.rs

Lines 155 to 178 in c859dff

	/// transform the plan node to only output the required columns ordered by index number, only
	/// logical plan node will use it, though all plan node impl it.
	fn prune_col(&self, required_cols: BitSet) -> PlanRef {
	let input_types = self.out_types();
	let mut need_prune = false;
	for i in 0..input_types.len() {
	if !required_cols.contains(i) {
	need_prune = true;
	}
	}
	if !need_prune {
	return self.clone_as_plan_ref();
	}
	let exprs = required_cols
	.iter()
	.map(|index| {
	BoundExpr::InputRef(BoundInputRef {
	index,
	return_type: input_types[index].clone(),
	})
	})
	.collect();
	LogicalProjection::new(exprs, self.clone_as_plan_ref()).into_plan_ref()
	}

[skyzh]

@lokax might have some ideas. I'll also take a look after I've settled down recently :)