xudong963 commented on pull request #1437:
URL: https://github.com/apache/arrow-datafusion/pull/1437#issuecomment-993467433
> > > This is an acceptable short term workaround, but I think it would be
more efficient and more elegant if we rewrite these recursive procedures into
iterative procedures.
>
> > Do you mean to use push-based model？
>
> @xudong963 , I think what @houqp is suggesting is to rewrite code that is
recursive to not be recursive.
>
> The pattern for Datafusion probably looks like taking code like
>
> ```rust
> fn visit(expr: &expr) {
> for child in expr.children() {
> visit(child)
> }
> // do actual expr logic
> }
> ```
>
> And changing it so the state is tracked with a structure on the heap
rather than a stack. I think
[`VecDeque`](https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html)
is a good one for rust:
>
> ```rust
> fn visit(expr: &expr) {
> let mut worklist = VecDequeue::new();
> worklist.push_back(expr);
> while !worklist.is_empty() {
> let parent = worklist.pop_front();
> for child in parent.children() {
> worklist.push_back(child)
> }
> // do actual expr logic on parent
> }
> }
> ```
>
> (aka avoid the call back to `visit`)
Open an issue https://github.com/apache/arrow-datafusion/issues/1444 to
track of this.
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