diff --git a/crates/fidc-core/src/data.rs b/crates/fidc-core/src/data.rs
index 74d953c..2995329 100644
--- a/crates/fidc-core/src/data.rs
+++ b/crates/fidc-core/src/data.rs
@@ -1386,7 +1386,12 @@ impl DataSet {
         mut bundles: Vec<DailySnapshotBundle>,
         execution_quotes: Vec<IntradayExecutionQuote>,
     ) -> Result<Self, DataSetError> {
-        bundles.sort_by_key(|bundle| bundle.date);
+        if !bundles
+            .windows(2)
+            .all(|window| window[0].date <= window[1].date)
+        {
+            bundles.sort_by_key(|bundle| bundle.date);
+        }
         if let Some(pair) = bundles.windows(2).find(|pair| pair[0].date == pair[1].date) {
             return Err(DataSetError::DuplicateDailyBundle { date: pair[1].date });
         }
@@ -1435,14 +1440,10 @@ impl DataSet {
                 |row| row.date,
                 |row| row.symbol.as_str(),
             )?;
-            bundle.market.sort_by(|left, right| left.symbol.cmp(&right.symbol));
+            sort_rows_by_symbol_if_needed(&mut bundle.market, |row| row.symbol.as_str());
             bundle.factors = normalize_factor_snapshots(bundle.factors);
-            bundle
-                .factors
-                .sort_by(|left, right| left.symbol.cmp(&right.symbol));
-            bundle
-                .candidates
-                .sort_by(|left, right| left.symbol.cmp(&right.symbol));
+            sort_rows_by_symbol_if_needed(&mut bundle.factors, |row| row.symbol.as_str());
+            sort_rows_by_symbol_if_needed(&mut bundle.candidates, |row| row.symbol.as_str());
             if !bundle.market.is_empty() {
                 grouped.market_by_date.insert(date, bundle.market);
             }
@@ -3844,6 +3845,18 @@ where
     }
 }
 
+fn sort_rows_by_symbol_if_needed<T, F>(rows: &mut Vec<T>, symbol_of: F)
+where
+    F: Fn(&T) -> &str + Copy,
+{
+    if !rows
+        .windows(2)
+        .all(|window| symbol_of(&window[0]) <= symbol_of(&window[1]))
+    {
+        rows.sort_by(|left, right| symbol_of(left).cmp(symbol_of(right)));
+    }
+}
+
 fn build_symbol_id_index(
     instruments: &HashMap<String, Instrument>,
     market_by_date: &BTreeMap<NaiveDate, Vec<DailyMarketSnapshot>>,