buraksenn commented on code in PR #20845:
URL: https://github.com/apache/datafusion/pull/20845#discussion_r2913693602


##########
datafusion/functions-aggregate/src/count.rs:
##########
@@ -365,31 +365,37 @@ impl AggregateUDFImpl for Count {
     }
 
     fn value_from_stats(&self, statistics_args: &StatisticsArgs) -> 
Option<ScalarValue> {
+        let [expr] = statistics_args.exprs else {
+            return None;
+        };
+        let col_stats = &statistics_args.statistics.column_statistics;
+
         if statistics_args.is_distinct {
+            // Only column references can be resolved from statistics;
+            // expressions like casts or literals are not supported.
+            let col_expr = 
expr.as_any().downcast_ref::<expressions::Column>()?;
+            if let Precision::Exact(dc) = 
col_stats[col_expr.index()].distinct_count {
+                return Some(ScalarValue::Int64(Some(dc as i64)));

Review Comment:
   Since other paths were casting as well I did not do it actually but let me 
do it for all paths



##########
datafusion/core/tests/physical_optimizer/aggregate_statistics.rs:
##########
@@ -402,3 +409,142 @@ async fn utf8_grouping_min_max_limit_fallbacks() -> 
Result<()> {
 
     Ok(())
 }
+
+fn mock_data_with_distinct_count(

Review Comment:
   I did not exactly understand but changed it to one table driven test



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