alamb commented on code in PR #10218:
URL: https://github.com/apache/datafusion/pull/10218#discussion_r1578667639
##########
datafusion/optimizer/src/eliminate_duplicated_expr.rs:
##########
@@ -35,78 +35,107 @@ impl EliminateDuplicatedExpr {
Self {}
}
}
-
+// use this structure to avoid initial clone
Review Comment:
```suggestion
/// Wrap the Expr in a Wrapper to support specialized comparison.
///
/// Ignores the sort options for `SortExpr` because if the expression is the
same
/// the subsequent exprs are never matched
///
/// For example, `ORDER BY a ASC a DESC` is the same
// as `ORDER BY a ASC` (the second `a DESC` is never compared)
```
##########
datafusion/optimizer/src/eliminate_duplicated_expr.rs:
##########
@@ -35,78 +36,111 @@ impl EliminateDuplicatedExpr {
Self {}
}
}
-
+// use this structure to avoid initial clone
+#[derive(Eq, Clone, Debug)]
+struct SortExprWrapper {
Review Comment:
This is very clever 👏
##########
datafusion/optimizer/src/eliminate_duplicated_expr.rs:
##########
@@ -35,78 +36,111 @@ impl EliminateDuplicatedExpr {
Self {}
}
}
-
+// use this structure to avoid initial clone
+#[derive(Eq, Clone, Debug)]
+struct SortExprWrapper {
+ expr: Expr,
+}
+impl PartialEq for SortExprWrapper {
+ fn eq(&self, other: &Self) -> bool {
+ match (&self.expr, &other.expr) {
+ (Expr::Sort(own_sort), Expr::Sort(other_sort)) => {
+ own_sort.expr == other_sort.expr
+ }
+ _ => self.expr == other.expr,
+ }
+ }
+}
+impl Hash for SortExprWrapper {
+ fn hash<H: Hasher>(&self, state: &mut H) {
+ match &self.expr {
+ Expr::Sort(sort) => {
+ sort.expr.hash(state);
+ }
+ _ => {
+ self.expr.hash(state);
+ }
+ }
+ }
+}
impl OptimizerRule for EliminateDuplicatedExpr {
fn try_optimize(
&self,
- plan: &LogicalPlan,
+ _plan: &LogicalPlan,
_config: &dyn OptimizerConfig,
) -> Result<Option<LogicalPlan>> {
+ internal_err!("Should have called EliminateDuplicatedExpr::rewrite")
+ }
+
+ fn apply_order(&self) -> Option<ApplyOrder> {
+ Some(ApplyOrder::TopDown)
+ }
+
+ fn supports_rewrite(&self) -> bool {
+ true
+ }
+
+ fn rewrite(
+ &self,
+ plan: LogicalPlan,
+ _config: &dyn OptimizerConfig,
+ ) -> Result<Transformed<LogicalPlan>> {
match plan {
LogicalPlan::Sort(sort) => {
- let normalized_sort_keys = sort
+ let len = sort.expr.len();
+ let normalized_sort_keys: Vec<_> = sort
.expr
- .iter()
- .map(|e| match e {
- Expr::Sort(ExprSort { expr, .. }) => {
- Expr::Sort(ExprSort::new(expr.clone(), true,
false))
- }
- _ => e.clone(),
- })
- .collect::<Vec<_>>();
+ .into_iter()
+ .map(|e| SortExprWrapper { expr: e })
+ .collect();
- // dedup sort.expr and keep order
- let mut dedup_expr = Vec::new();
- let mut dedup_set = HashSet::new();
- sort.expr.iter().zip(normalized_sort_keys.iter()).for_each(
- |(expr, normalized_expr)| {
- if !dedup_set.contains(normalized_expr) {
- dedup_expr.push(expr);
- dedup_set.insert(normalized_expr);
- }
- },
- );
- if dedup_expr.len() == sort.expr.len() {
- Ok(None)
- } else {
- Ok(Some(LogicalPlan::Sort(Sort {
- expr:
dedup_expr.into_iter().cloned().collect::<Vec<_>>(),
- input: sort.input.clone(),
- fetch: sort.fetch,
- })))
+ let mut index_set = IndexSet::new(); // use index_set instead
of Hashset to preserve order
Review Comment:
This is also quite clever
I think you can avoid a Vec here if you skip `normalized_sort_keys` and
create `unique_exprs` directly, as you did below.
Something like
```rust
let unique_exprs: Vec<Expr> = sort
.expr
.into_iter()
// use SortExpr wrapper to ignore sort options
.map(|e| SortExprWrapper { expr: e })
.collect::<IndexSet<_>>()
.into_iter()
.map(|wrapper| wrapper.expr)
.collect();
```
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