jayzhan211 commented on code in PR #10386:
URL: https://github.com/apache/datafusion/pull/10386#discussion_r1590494745
##########
datafusion/optimizer/src/simplify_expressions/expr_simplifier.rs:
##########
@@ -1670,17 +1734,106 @@ fn inlist_except(mut l1: InList, l2: InList) ->
Result<Expr> {
Ok(Expr::InList(l1))
}
+pub struct RewriteCycle {
+ consecutive_unchanged_count: usize,
+ total_iterations: usize,
+ num_rewriters: usize,
+}
+pub type RewriteCycleResult = ControlFlow<Result<Expr>, Expr>;
+
+impl RewriteCycle {
+ fn new() -> Self {
+ RewriteCycle {
+ // use usize::MAX as default to avoid checking null in is_done()
comparison
+ // real value is set later by record_num_rewriters
+ num_rewriters: usize::MAX,
+ consecutive_unchanged_count: 0,
+ total_iterations: 0,
+ }
+ }
+
+ pub fn completed_cycles(&self) -> usize {
+ // default value indicates we have not completed a cycle
+ if self.num_rewriters == usize::MAX {
+ 0
+ } else {
+ self.total_iterations / self.num_rewriters
+ }
+ }
+
+ pub fn total_iterations(&self) -> usize {
+ self.total_iterations
+ }
+
+ fn record_num_rewriters(&mut self) {
+ self.num_rewriters = self.total_iterations;
+ }
+
+ fn is_done(&self) -> bool {
+ self.consecutive_unchanged_count >= self.num_rewriters
Review Comment:
The logic to stop looping is checking if `transformed` meet the num of
rewriters, but can we just stop if any of the `transformed` is false? I think
it is more straightforward and we don't need to have a `max_iter` num too.
Idea is something like
```rust
loop {
transformed |= rewrite_rule()
if not transformed {
return
}
}
```
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