fix(tables): preserve columns in DefaultTableManager exports#9258
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mscolnick
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Apr 18, 2026
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Pull request overview
This PR improves DefaultTableManager export/selection behavior so heterogeneous row-oriented data and mismatched-length column-oriented data preserve all columns/rows consistently (instead of silently omitting them).
Changes:
- Infer row-oriented column names by unioning keys across the first
1000rows (first-seen order). - Normalize column-oriented dict-of-lists using
zip_longest(..., fillvalue=None)and compute row count as the longest column. - Make row-oriented
select_columns()resilient to missing keys by usingrow.get(...)(fills withNone).
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
marimo/_plugins/ui/_impl/tables/default_table.py |
Updates column inference, normalization, selection behavior, and row counting to preserve columns/rows in exports. |
tests/_plugins/ui/_impl/tables/test_default_table.py |
Adds coverage for heterogeneous row keys and mismatched column lengths in CSV/JSON and helpers. |
…n lengths in DefaultTableManager exports
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📝 Summary
Closes https://github.com/marimo-team/qa-agent/issues/12
get_column_names()now unions keys across first1000rows. previously we checked only first row_normalize_data()pads short columns withNonewithzip_longest. Prevents row omission in column-oriented dataselect_columns()on row-oriented data usesrow.get(key)instead ofrow[key]. Missing keys becomeNonerather than raisingKeyError.get_num_rows()for column-oriented data returns the longest column length, matching normalized output.