# Polars 1.31.0-beta.1 — Python Polars 1.31.0-beta.1

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2025-06-14
- Version: 1.31.0-beta.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.31.0-beta.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.31.0-beta.1
- Labels: Pre-release

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **removed** — Remove old streaming engine
- **deprecated** — Deprecate allow_missing_columns in scan_parquet in favor of missing_columns
- **changed** — Move row index materialization in post-apply to occur after slicing
- **added** — Add first_(true|false)_idx to BooleanChunked and use in bool arg_(min|max)
- **changed** — Don't go through row encoding for most types on index_of
- **changed** — Optimise low-level null scans and arg_max for bools when chunked
- **added** — DataType expressions in Python
- **added** — Native implementation for Iceberg positional deletes
- **added** — Basic implementation of DataTypeExpr in Rust DSL
- **added** — Add required: bool to ParquetFieldOverwrites
- **added** — Support serializing name.map_fields
- **added** — Support serializing Expr::RenameAlias
- **added** — Add keys column in finish_callback
- **added** — Add extra_columns parameter to scan_parquet
- **added** — Add CORR function to polars SQL
- **added** — Add per partition sort and finish callback to sinks
- **changed** — Support descendingly-sorted values in search_sorted()
- **added** — Derive DSL schema
- **fixed** — Fix panic reading empty parquet with multiple boolean columns
- **fixed** — Raise ComputeError instead of panicking in truncate when mixing month/week/day/sub-daily units
- **fixed** — Materialize list.eval with unknown type

##### 💥 Breaking changes

- Remove old streaming engine (#23103)

##### ⚠️ Deprecations

- Deprecate `allow_missing_columns` in `scan_parquet` in favor of `missing_columns` (#22784)

##### 🚀 Performance improvements

- Improve streaming groupby CSE (#23092)
- Move row index materialization in post-apply to occur after slicing (#22995)
- Add first\_(true|false)\_idx to BooleanChunked and use in bool arg\_(min|max) (#22907)
- Don't go through row encoding for most types on `index_of` (#22903)
- Optimise low-level `null` scans and `arg_max` for bools (when chunked) (#22897)
- Optimize multiscan performance (#22886)

##### ✨ Enhancements

- DataType expressions in Python (#23167)
- Native implementation for Iceberg positional deletes (#23091)
- Remove old streaming engine (#23103)
- Basic implementation of `DataTypeExpr` in Rust DSL (#23049)
- Add `required: bool` to `ParquetFieldOverwrites` (#23013)
- Support serializing `name.map_fields` (#22997)
- Support serializing `Expr::RenameAlias` (#22988)
- Remove duplicate verbose logging from `FetchedCredentialsCache` (#22973)
- Add `keys` column in `finish_callback` (#22968)
- Add `extra_columns` parameter to `scan_parquet` (#22699)
- Add CORR function to polars SQL (#22690)
- Add per partition sort and finish callback to sinks (#22789)
- Support descendingly-sorted values in search\_sorted() (#22825)
- Derive DSL schema (#22866)

##### 🐞 Bug fixes

- Fix panic reading empty parquet with multiple boolean columns (#23159)
- Raise ComputeError instead of panicking in `truncate` when mixing month/week/day/sub-daily units (#23176)
- Materialize `list.eval` with unknown type (#23186)
- Only set sorting flag for 1st column with PQ SortingColumns (#23184)
- Typo in AExprBuilder (#23171)
- Null return from var/std on scalar column (#23158)
- Support Datetime broadcast in `list.concat` (#23137)
- Ensure projection pushdown maintains right table schema (#22603)
- Add Null dtype support to arg\_sort\_by (#23107)
- Raise error by default on invalid CSV quotes (#22876)
- Fix group\_by mean and median returning all nulls for Decimal dtype (#23093)
- Fix hive partition pruning not filtering out `__HIVE_DEFAULT_PARTITION__` (#23074)
- Fix `AssertionError` when using `scan_delta()` on AWS with `storage_options` (#23076)
- Fix deadlock on `collect(background=True)` / `collect_concurrently()` (#23075)
- Incorrect null count in rolling\_min/max (#23073)
- Preserve `file://` in LazyFrame node traverser (#23072)
- Respect column order in `register_io_source` schema (#23057)
- Don't call unnest for objects implementing `__arrow_c_array__` (#23069)
- Incorrect output when using `sort` with `group_by` and `cum_sum` (#23001)
- Implement owned arithmetic for Int128 (#23055)
- Do not schema-match structs with different field counts (#23018)
- Fix confusing error message on duplicate row\_index (#23043)
- Add `include_nulls` to `Agg::Count` CSE check (#23032)
- View buffer exceeding 2^32 - 1 bytes in concatenate\_view (#23017)
- Fix incorrect result selecting `pl.len()` from `scan_csv` with `skip_lines` (#22949)
- Allow for IO plugins with reordered columns in streaming (#22987)
- Method `str.zfill` was inconsistent with Python and pandas when string contained leading '+' (#22985)
- Integer underflow in `propagate_nulls` (#22986)
- Setting `compat_level=0` for `sink_ipc` (#22960)
- Narrow return type for `DataType.is_`, improve Pyright's type completeness from 69% to 95% (#22962)
- Support arrow Decimal32 and Decimal64 types (#22954)
- Guard against dictionaries being passed to projection keywords (#22928)
- Update arrow format (#22941)
- Fix filter pushdown to IO plugins (#22910)
- Improve numeric stability rolling\_mean\<f32> (#22944)
- Guard against invalid nested objects in 'map\_elements' (#22932)
- Allow subclasses in type equality checking (#22915)
- Return early in `pl.Expr.__array_ufunc__` when only single input (#22913)
- Add inline implodes in type coercion (#22885)
- Add {top, bottom}\_k\_by to Ser

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.31.0-beta.1]_