fix: write parquet with 50k row groups instead of single giant row group

hub-stats.py

@@ -215,8 +215,14 @@ def jsonl_to_parquet(endpoint, jsonl_file, output_file):
     combined_df = pd.concat(all_dfs, ignore_index=True)
     total_rows = len(combined_df)
 
-    # Write to parquet
-    combined_df.to_parquet(output_file, index=False, engine="pyarrow")
+    # Write to parquet with controlled row group sizes
+    row_group_size = 50_000
+    table = pa.Table.from_pandas(combined_df, preserve_index=False)
+    writer = pq.ParquetWriter(output_file, table.schema)
+    for i in range(0, total_rows, row_group_size):
+        chunk = table.slice(i, min(row_group_size, total_rows - i))
+        writer.write_table(chunk)
+    writer.close()
 
     return total_rows