goldmedal commented on code in PR #13028:
URL: https://github.com/apache/datafusion/pull/13028#discussion_r1809054261
##########
datafusion/optimizer/src/eliminate_limit.rs:
##########
@@ -63,17 +63,23 @@ impl OptimizerRule for EliminateLimit {
> {
match plan {
LogicalPlan::Limit(limit) => {
- if let Some(fetch) = limit.fetch {
- if fetch == 0 {
+ // Only supports rewriting for literal fetch
+ let FetchType::Literal(fetch) = limit.get_fetch_type()? else {
+ return Ok(Transformed::no(LogicalPlan::Limit(limit)));
+ };
+
+ if let Some(v) = fetch {
+ if v == 0 {
return Ok(Transformed::yes(LogicalPlan::EmptyRelation(
EmptyRelation {
produce_one_row: false,
schema: Arc::clone(limit.input.schema()),
},
)));
}
- } else if limit.skip == 0 {
- // input also can be Limit, so we should apply again.
+ } else if matches!(limit.get_skip_type()?,
SkipType::Literal(0)) {
+ // If fetch is `None` and skip is 0, then Limit takes no
effect and
+ // we can remove it. Its input also can be Limit, so we
should apply again.
return Ok(self
.rewrite(Arc::unwrap_or_clone(limit.input), _config)
.unwrap());
Review Comment:
```suggestion
.rewrite(Arc::unwrap_or_clone(limit.input),
_config)?);
```
Just noticed this point. It's better to return an error instead of a panic.
Could you help to improve it?
##########
datafusion/expr/src/expr_rewriter/mod.rs:
##########
@@ -308,7 +308,10 @@ impl NamePreserver {
Self {
// The schema of Filter and Join nodes comes from their inputs
rather than their output expressions,
Review Comment:
```suggestion
// The schema of Filter, Join, and Limit nodes comes from their
inputs rather than their output expressions,
```
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