FIX: Performance of DBNStore.to_df with pretty_ts

Author: nmacholl

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 #### Bug fixes
 - Fixed issue where a large unreadable symbol subscription message could be sent
+- Fixed an issue where `DBNStore.to_df` with `pretty_ts=True` was very slow
 
 ## 0.22.1 - 2023-10-24
 

databento/common/dbnstore.py

@@ -7,7 +7,6 @@
 import warnings
 from collections.abc import Generator
 from collections.abc import Iterator
-from functools import partial
 from io import BytesIO
 from os import PathLike
 from pathlib import Path
@@ -1246,9 +1245,7 @@ def _format_px(
 
     def _format_pretty_ts(self, df: pd.DataFrame) -> None:
         for field in self._struct._timestamp_fields:
-            df[field] = df[field].apply(
-                partial(pd.to_datetime, utc=True, errors="coerce"),
-            )
+            df[field] = pd.to_datetime(df[field], utc=True, errors="coerce")
 
     def _format_set_index(self, df: pd.DataFrame) -> None:
         index_column = (