# Polars 1.22.0 — Python Polars 1.22.0

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2025-02-08
- Version: 1.22.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.22.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.22.0

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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- **changed** — Reduce sharing in stringview arrays in new-streaming equijoin
- **changed** — Implement native Expr.count() on new-streaming
- **changed** — Speed up list operations that use amortized_iter()
- **changed** — Use Cow as output for rechunk and add rechunk_mut
- **changed** — Reduce arrow slice mmap overhead
- **changed** — Reduce conversion cost in chunked string gather
- **changed** — Enable prefiltered by default for new streaming
- **changed** — Enable parquet column expressions for streaming
- **changed** — Deduplicate buffers again in stringview concat kernel
- **added** — Add dedicated concatenate kernels
- **changed** — Rechunk only once during join probe gather
- **changed** — Change default memory prefetch to MADV_WILLNEED
- **changed** — Remove cast to boolean after comparison in optimizer
- **changed** — Speed up from_pandas when converting frame with multi-index columns
- **added** — Add projection pushdown to new streaming multiscan
- **added** — Implement join on struct dtype
- **changed** — Use unique temporary directory path per user and restrict permissions
- **added** — Enable ingest of objects supporting the PyCapsule interface via from_arrow
- **added** — Enable new streaming multiscan for CSV
- **added** — Add environment POLARS_MAX_CONCURRENT_SCANS in multiscan for new streaming
- **fixed** — Fix Expr.over applying scale incorrectly for Decimal types

##### 🚀 Performance improvements

- Reduce sharing in stringview arrays in new-streaming equijoin (#21129)
- Implement native Expr.count() on new-streaming (#21126)
- Speed up list operations that use amortized\_iter() (#20964)
- Use Cow as output for rechunk and add rechunk\_mut (#21116)
- Reduce arrow slice mmap overhead (#21113)
- Reduce conversion cost in chunked string gather (#21112)
- Enable prefiltered by default for new streaming (#21109)
- Enable parquet column expressions for streaming (#21101)
- Deduplicate buffers again in stringview concat kernel (#21098)
- Add dedicated concatenate kernels (#21080)
- Rechunk only once during join probe gather (#21072)
- Micro-optimise internal `DataFrame` height and width checks (#21071)
- Speed up from\_pandas when converting frame with multi-index columns (#21063)
- Change default memory prefetch to MADV\_WILLNEED (#21056)
- Remove cast to boolean after comparison in optimizer (#21022)
- Split last rowgroup among all threads in new-streaming parquet reader (#21027)
- Recombine into larger morsels in new-streaming join (#21008)
- Improve `list.min` and `list.max` performance for logical types (#20972)
- Ensure count query select minimal columns (#20923)

##### ✨ Enhancements

- Add projection pushdown to new streaming multiscan (#21139)
- Implement join on struct dtype (#21093)
- Use unique temporary directory path per user and restrict permissions (#21125)
- Enable ingest of objects supporting the PyCapsule interface via `from_arrow` (#21128)
- Enable new streaming multiscan for CSV (#21124)
- Environment `POLARS_MAX_CONCURRENT_SCANS` in multiscan for new streaming (#21127)
- Ensure AWS credential provider sources AWS\_PROFILE from environment after deserialization (#21121)
- Multi/Hive scans in new streaming engine (#21011)
- Add `linear_spaces` (#20941)
- IO plugins suppport lazy schema (#21079)
- Add `write_table()` function to Unity catalog client (#21089)
- Add `is_object` method to Polars `DataType` class (#21074)
- Implement `merge_sorted` for binary (#21045)
- Hold string cache in new streaming engine and fix row-encoding (#21039)
- Add CredentialProviderAzure parameter to accept user-instantiated azure credential classes (#21047)
- Expose unity catalog dataclasses and type aliases (#21046)
- Support max/min method for Time dtype (#19815)
- Implement a streaming merge sorted node (#20960)
- Automatically use temporary credentials API for scanning Unity catalog tables (#21020)
- Add negative slice support to new-streaming engine (#21001)
- Allow for more RG skipping by rewriting expr in planner (#20828)
- Rename catalog `schema` to `namespace` (#20993)
- Add functionality to create and delete catalogs, tables and schemas to Unity catalog client (#20956)
- Allow custom JSONEncoder for the `json_normalize` function, minor speedup (#20966)
- Support passing `aws_profile` in `storage_options` (#20965)
- Improved support for KeyboardInterrupts (#20961)
- Make the available `concat` alignment strategies more generic (#20644)
- Extract  timezone info from python datetimes (#20822)
- Add hint for `POLARS_AUTO_USE_AZURE_STORAGE_ACCOUNT_KEY` to error message (#20942)
- Filter Parquet pages with `ParquetColumnExpr` (#20714)
- Expose descending and nulls last in window order-by (#20919)

##### 🐞 Bug fixes

- Fix `Expr.over` applying scale incorrectly for Decimal types (#21140)
- Fix IO plugin predicate with failed serialization (#21136)
- Ensure `lit` handles datetimes with tzinfo that represents a fixed offset from UTC (#21003)
- Correctly implement take\_(opt\_)chunked\_unchecked for structs (#21134)
- Restore printing backtraces on panics (#21131)
- Use microseconds for Unity catalog datetime unit (#21122)
- Fix incorrect output height for SQL `SELECT COUNT(*) FROM` (#21108)
- Validate/coerce types for comparisons within join\_where predicates (#21049)
- Do not auto-init credential providers if credential fetch returns error (#21090)
- Fix `join_where` incorrectly dropping tra

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