howiezhao opened a new pull request, #4780: URL: https://github.com/apache/cassandra/pull/4780
## Issue `COPY TO` followed by `COPY FROM` corrupts string values containing backslashes on Python 3.10+: the backslash count doubles on every round-trip. For example, `https:\/\/google.com` becomes `https:\\/\\/google.com` after one cycle. ## RC There are two independent backslash-escaping layers in the COPY pipeline: 1. **`format_value_text`** (pre-doubling, always present): doubles every `\` → `\\` before passing to `csv.writer` 2. **`csv.writer` escapechar handling** (Python-version-dependent): Python 3.10 fixed [bpo-12178](https://bugs.python.org/issue12178), making `csv.writer` properly escape `\` → `\\` in all fields Before Python 3.10, `csv.writer` did **not** escape bare backslashes in unquoted fields, so the pre-doubling from `format_value_text` was exactly cancelled by `csv.reader` on import. After Python 3.10, both layers apply, but `csv.reader` only removes one — leaving the value with doubled backslashes. ## Fix In `ExportProcess.format_value`, undo `format_value_text`'s pre-doubling on Python 3.10+ before handing the value to `csv.writer`, making `csv.writer` the sole escaping layer: ```python if sys.version_info >= (3, 10): formatted = formatted.replace('\\\\', '\\') ``` No change for Python < 3.10. <img width="883" height="725" alt="Screenshot 2026-04-30 at 17 46 36" src="https://github.com/user-attachments/assets/7160d7d0-a8a5-4862-aa78-60a160be4f8e"; /> -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
