chore: some cleanup

Author: mohammadnaqvi04

datafusion/optimizer/src/decorrelate.rs

@@ -77,11 +77,11 @@ pub struct PullUpCorrelatedExpr {
     pub pulled_up_scalar_agg: bool,
     /// A correlated column wrapped in an expression (e.g. `CAST(t2.b AS INT)`)
     /// gets grouped by that entire expression instead of the bare column,
-    /// aliased to a generated name, once, in the `Aggregate` this column belongs to. Every
-    /// later reference to that column, in a `Projection` above it for
-    /// instance, needs to use the same alias instead of the now
-    /// unresolvable bare column. This records the mapping the first
-    /// time it's made.
+    /// aliased to a generated name, once, in the `Aggregate` this column
+    /// belongs to. Every later reference to that column, in a
+    /// `Projection` above it for instance, needs to use the same alias
+    /// instead of the now unresolvable bare column. This records the
+    /// mapping the first time it's made.
     correlated_col_aliases: HashMap<Column, Expr>,
     /// `LIMIT 0` forces the subquery to zero rows unconditionally, regardless
     /// of whether the correlation matched, collapsing it to an `EmptyRelation`.

datafusion/optimizer/src/decorrelate_predicate_subquery.rs

@@ -675,7 +675,7 @@ fn build_join_with_count_bug(
 ) -> Result<LogicalPlan> {
     if in_predicate_opt.is_some() {
         return not_impl_err!(
-            "build_join_with_count_bug: `IN`/`NOT IN` count-bug compensation is not implemented"
+            "IN/NOT IN count-bug compensation for groupless aggregates is not implemented"
         );
     }
 
@@ -719,12 +719,14 @@ fn build_join_with_count_bug(
     };
 
     // EXISTS is true by default (the groupless aggregate always
-    // produces a row), unless one of three cases holds: (1) the outer
-    // row joined against an inner group whose HAVING predicate failed,
+    // produces a row), unless one of three cases holds:
+    // (1) the outer row joined against an inner group whose HAVING
+    //     predicate failed,
     // (2) an unmatched outer row's own default aggregate values fail
-    // that same HAVING clause, or (3) the subquery was truncated to
-    // zero rows unconditionally (LIMIT 0), which is false for every
-    // outer row regardless of whether it matched.
+    //     that same HAVING clause,
+    // (3) the subquery was truncated to zero rows unconditionally
+    //     (LIMIT 0), which is false for every outer row regardless of
+    //     whether it matched.
     let exists_expr = if forces_empty_result {
         lit(false)
     } else {