try removing caching and catch empty result

app.py

@@ -57,6 +57,10 @@ def load_parquet_to_duckdb(con, parquet_url, view_name):
 # DuckDB connection (global)
 con = duckdb.connect(database=":memory:", read_only=False)
 
+# disable all caching so HF Spaces always read latest parquet
+con.execute("SET enable_http_metadata_cache = false;")
+con.execute("SET enable_object_cache = false;")
+
 # Load parquet files from Hugging Face using DuckDB
 HF_DATASET_ID = "mmpr/open_model_evolution_data"
 hf_parquet_url_1 = "https://huggingface.co/datasets/mmpr/open_model_evolution_data/resolve/main/all_downloads_with_annotations.parquet"
@@ -878,10 +882,27 @@ def _leaderboard_callback_logic(
         slider_value, group_col, top_n, view=view
     )
 
+    # If the SQL query returned no rows, ask user to broaden date range
+    if df_filtered is None or df_filtered.empty:
+        msg = html.Div(
+            "No data found in this time range. Try broadening the download date range.",
+            style={"padding": "18px", "fontSize": "16px", "color": "#082030"},
+        )
+        return msg, new_label
+
     # Process the already-filtered data - pass derived_author_toggle
     df, download_df = get_top_n_leaderboard(
         df_filtered, group_col, top_n, derived_author_toggle=derived_author_toggle
     )
+
+    # If processing produced no rows, ask user to broaden date range
+    if df is None or (hasattr(df, "empty") and df.empty):
+        msg = html.Div(
+            "No data found in this time range. Try broadening the download date range.",
+            style={"padding": "18px", "fontSize": "16px", "color": "#082030"},
+        )
+        return msg, new_label
+
     return render_table_content(
         df, download_df, chip_color=chip_color, filename=filename
     ), new_label