# Polars changelog

> A DataFrame library built on Apache Arrow with a lazy query engine.

- Vendor: Polars
- Category: Frameworks & Libraries
- Official site: https://pola.rs
- Tracked by: What's New (https://whatsnew.fyi/product/polars)
- Harvested from: GitHub (pola-rs/polars)
- Entries below: 25 (newest first)

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'.

## Releases

### 1.43.2 — Python Polars 1.43.2

- Date: 2026-08-01
- Version: 1.43.2
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.43.2
- Permalink: https://whatsnew.fyi/product/polars/releases/1.43.2

- **deprecated** — Deprecate casts from Categorical to integer dtypes
- **deprecated** — Deprecate not setting the plan_stage argument in show_graph()
- **changed** — Pushdown len() to concat/union inputs
- **security** — Issue FutureWarning on using from_arrow of ArrowStreamExportable
- **added** — Add infer_schema_files parameter to scan_csv
- **fixed** — Properly propagate enum metadata for iceberg column mapping
- **fixed** — Correctly write parquet field IDs for enums and categoricals
- **fixed** — Fix arrow C interop binview offset
- **fixed** — Fix duplicate hive values in hive pre-partition rewrite
- **fixed** — Double-counted offset for Arrow export of sliced Series(Array)
- **fixed** — Struct/List/Array equality handling in sort and join
- **fixed** — More careful slice pushdown into joins
- **fixed** — Preserve ordering in sliced unions
- **fixed** — Drop input sortedness when casting to a string
- **fixed** — Clear sortedness flags in StringChunked substring kernels
- **fixed** — Bad mask handling when reading optional parquet column
- **fixed** — Any operation on Unknown(Int) and Unknown(Float) should result in Unknown(Float)
- **fixed** — Flip nulls_last after Expr.reverse()
- **fixed** — Fix high blocking thread use in sink_parquet with async local path
- **fixed** — Serialize LazyFrames backed by bytes

##### ⚠️ Deprecations

- Deprecate casts from `Categorical` to integer dtypes (#28525)
- Deprecate not setting the `plan_stage` argument in `show_graph()` (#28391)

##### 🚀 Performance improvements

- Pushdown `len()` to concat/union inputs (#28570)

##### ✨ Enhancements

- Issue FutureWarning on using `from_arrow` of ArrowStreamExportable (#28442)
- Add `infer_schema_files` parameter to `scan_csv` (#28440)

##### 🐞 Bug fixes

- Properly propagate enum metadata for iceberg column mapping (#28580)
- Correctly write parquet field IDs for enums and categoricals (#28581)
- Fix arrow C interop binview offset (#28623)
- Fix duplicate hive values in hive pre-partition rewrite (#28621)
- Double-counted offset for Arrow export of sliced `Series(Array)` (#28602)
- Struct/List/Array equality handling in sort and join (#28601)
- More careful slice pushdown into joins (#28578)
- Preserve ordering in sliced unions (#28576)
- Drop input sortedness when casting to a string (#28574)
- Clear sortedness flags in `StringChunked` substring kernels (#28573)
- Bad mask handling when reading optional parquet column (#28547)
- Any operation on `Unknown(Int)` and `Unknown(Float)` should result in `Unknown(Float)` (#28545)
- Flip `nulls_last` after `Expr.reverse()` (#28572)
- Fix high blocking thread use in sink\_parquet with async local path (#28543)
- Serialize LazyFrames backed by bytes (#28568)
- Release GIL in `SQLContext.execute()` (#28549)
- Propagate `nulls_last` in `function_expr_sortedness` (#28544)
- Incorrect slicing when a join requires sorting (#28541)

##### 🛠️ Other improvements

- Fix duckdb delta extension install collision (#28607)

Thank you to all our contributors for making this release possible!
@BitWeaverDev, @Matt711, @Samoilov2004, @borchero, @dancsi, @dsprenkels, @kdn36, @masumi-ryugo, @nameexhaustion and @ritchie46

### 1.43.1 — Python Polars 1.43.1

- Date: 2026-07-27
- Version: 1.43.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.43.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.43.1

- **changed** — Optimize not(bool_f) to not_bool_f
- **added** — Allow callback sinks on cloud
- **fixed** — Fix panic on self join of scan_delta / scan_iceberg
- **fixed** — Fix UB on first/last_non_null with empty chunk
- **fixed** — Do not CSE non-column height expr on streaming engine
- **fixed** — Propagate adjusted sortedness through Gather
- **fixed** — Deduplicate the expression equality checks
- **fixed** — Address 3VL issue with SQL NOT IN interaction with NULL values and joins
- **fixed** — Use total comparison in Expr literal values
- **fixed** — Ensure SQL SUM and CORR aggregates return NULL for all-null inputs, add TOTAL
- **fixed** — Share null_count_dtype helper between Delta and Iceberg, fixing SchemaError
- **fixed** — Remove non-output columns from the equi-join and semi/anti-join operators
- **fixed** — Fix dropped slice on multiple unions
- **fixed** — Fix in-memory engine incorrect slice on maintain order join
- **fixed** — Check join schema by position
- **fixed** — Block predicate pushdown past overwritten window keys
- **added** — Make hive_part extraction a function and public

##### 🚀 Performance improvements

- Optimize not(bool\_f) to not\_bool\_f (#28474)

##### ✨ Enhancements

- Allow callback sinks on cloud (#28458)

##### 🐞 Bug fixes

- Fix panic on self join of scan\_delta / scan\_iceberg (#28468)
- Fix UB on first/last\_non\_null with empty chunk (#28495)
- Do not CSE non-column height expr on streaming engine (#28480)
- Propagate adjusted sortedness through Gather (#28493)
- Deduplicate the expression equality checks (#28483)
- Address 3VL issue with SQL `NOT IN` interaction with `NULL` values and joins (#28484)
- Use total comparison in Expr literal values (#28482)
- Ensure SQL `SUM` and `CORR` aggregates return NULL for all-null inputs, add `TOTAL` (#28475)
- Share `null_count_dtype` helper between Delta and Iceberg, fixing `SchemaError` (#28479)
- Remove non-output columns from the equi-join and semi/anti-join operators (#28446)
- Fix dropped slice on multiple unions (#28477)
- Fix in-memory engine incorrect slice on maintain order join (#28478)
- Check join schema by position (#28455)
- Block predicate pushdown past overwritten window keys (#28429)

##### 📖 Documentation

- Update and restructure README (#28490)
- Minor fixes to Spark migration guide (#27730)
- Relocate Polars Cloud \& On-Prem User Guide (#28462)
- Add notes on k8s operator (#28445)

##### 🛠️ Other improvements

- Make hive\_part extraction a function and public (#28507)
- Deduplicate the expression equality checks (#28483)
- Bump `ruff` and `mypy` package versions (#28456)
- Fix flaky test (#28454)

Thank you to all our contributors for making this release possible!
@AnirudhRahul, @EndPositive, @Jesse-Bakker, @alexander-beedie, @carnarez, @dancsi, @mdroogh, @mroeschke, @nameexhaustion, @nchammas, @orlp, @r-brink and @ritchie46

### 1.43.0 — Python Polars 1.43.0

- Date: 2026-07-21
- Version: 1.43.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.43.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.43.0

- **deprecated** — Deprecate casting numeric types to categoricals
- **deprecated** — Deprecate cat.get_categories() and cat.to_local()
- **deprecated** — Deprecate LazyFrame.profile()
- **deprecated** — Deprecate casts from non-nested dtypes into Lists
- **deprecated** — Deprecate bitwise ops between integers and booleans
- **deprecated** — Deprecate list/arr.to_struct() calls that don't pass field names
- **changed** — Rename missing_utf8_is_empty_string to empty_string_is_null
- **changed** — Split multiplexers that directly scan from in-memory DataFrame
- **changed** — Make DNS cache global
- **changed** — Pre-partition on left, right and semi joins on hive partitioned data
- **changed** — Rewrite inner joins on hive partitioned data to a union of partitions filtered joins
- **added** — Add ewm_sum and ewm_sum_by
- **added** — Add scan_arrow_c_stream
- **added** — Support Iceberg field initial-default in native scan_iceberg
- **added** — Add Series.degrees/radians and clarify trig functions use radians
- **added** — Add list expression which consistently packs elements together into new List type
- **added** — Add Expr.cat.to and Expr.cat.physical
- **added** — Add POLARS_OOC_DISK_BUDGET_MB
- **added** — Add build side preference parameter for join
- **fixed** — Avoid panic when union slice skips all rows
- **fixed** — Solve panic in dt.replace when there were multiple chunks

##### ⚠️ Deprecations

- Deprecate casting numeric types to categoricals (#28349)
- Deprecate `cat.get_categories()` and `cat.to_local()` (#28299)
- Deprecate `LazyFrame.profile()` (#28275)
- Deprecate casts from non-nested dtypes into Lists (#28193)
- Deprecate bitwise ops between integers and booleans (#28186)
- Deprecate `list/arr.to_struct()` calls that don't pass field names (#28243)
- Rename `missing_utf8_is_empty_string` to `empty_string_is_null` (#28173)

##### 🚀 Performance improvements

- Split multiplexers that directly scan from in-memory DataFrame (#28376)
- Make DNS cache global (#28352)
- Do not remove cache if predicates not pushed to all inputs (#28341)
- Environment variable for logging slow DNS lookup (#28211)
- Pre-partition on left, right and semi joins on hive partitioned data (#28374)
- Rewrite inner joins on hive partitioned data to a union of partitions filtered joins (#28327)
- Tighten redundant comparisons and propagate filter constraints (#27999)
- Canonicalize predicates (#28212)
- Remove excess memory copy in streaming IPC sink (#28141)
- Parallelize scan\_iceberg resolve (#28168)
- Chunk-aware morsel splitting on single-file IO sink (#27950)
- Don't allocate for `full_null()` with small lengths (#28181)
- Use monotonic deque for rolling min\_by/max\_by (O(n)) (#27436)

##### ✨ Enhancements

- Pre-partition group-by on hive keys  (#28444)
- Add ewm\_sum and ewm\_sum\_by #28151 (#28215)
- Serve stale records from object\_store DNS cache (#28256)
- Make partition\_hive an opt flag (#28345)
- Add `scan_arrow_c_stream` (#28340)
- When displaying IRExprs, only add parentheses when needed for disambiguation (#28319)
- Support Iceberg field `initial-default` in native `scan_iceberg` (#28324)
- Show only differing dtypes in `assert_frame_equal` error (#27816)
- Expose ewm and rolling \*\_by expressions in Python visitor (#28286)
- More accurate rolling moments (#28309)
- Remove hard block on native scan for Iceberg V3 tables (#28277)
- Add Series.degrees/radians and clarify trig functions use radians (#22961)
- Merge sorted with multikey (#28067)
- Add `list` expression which consistently packs elements together into new List type (#27990)
- Add `read_database` Arrow fast-path for "python-oracledb" (#28230)
- Optimize joins with redundant equi-join keys (#28017)
- Implement missing datetime options for `CastColumnsPolicy` (#28084)
- Add Expr.cat.to and Expr.cat.physical (#28096)
- Add POLARS\_OOC\_DISK\_BUDGET\_MB (#28045)
- Add build side preference parameter for join (#28154)

##### 🐞 Bug fixes

- Avoid panic when union slice skips all rows (#28420)
- Solve panic in `dt.replace` when there were multiple chunks (#28437)
- Propagate `is_scalar` from the input to the output of `.sort()` and `.sort_by()` (#28438)
- Resolve CSV column names overwrite in DSL->IR conversion (#28383)
- Avoid IEJoin rewrite for Categorical comparisons (#28427)
- Do not rewrite `sort().reverse()` to `sort(descending=True)` when `maintain_order=True` (#28403)
- Ensure BinaryView offset+len does not exceed i32::MAX where possible (#28048)
- Invalid offset in strptime (#28388)
- Incorrect schema type for decimal \<-> primitive division (#28373)
- Panic in in-memory CSEE handling (#28371)
- Fix offset in arrow ffi export of sliced struct arrays (#28369)
- Fix cross filter not applied with sink and CSE (#28297)
- Fix panic on projection pushdown with caches (#28280)
- Fix `write_json()` null values in `Array` columns being written incorrectly as `null` (#28330)
- Fix EntityTooSmall on sink\_ipc to S3 (#28255)
- Raise error instead of silent wrapping for `select(len())` (#28355)
- Float16 groupby aggregates (#28361)
- Respect lexical ordering of Categorical in `top_k`/`bottom_k` (#28359)
- Support dtype-list schema overrides in scan\_csv (#28226)
- Resolve unknown type in fused multiply add (#28321)
- Honor `aws_checksum_algorithm` when provided (#28328)
- Remove usage of deprecated `pyarrow.feather.read_table` (#28323)
- Fix regress

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.43.0]_

### 1.42.1 — Python Polars 1.42.1

- Date: 2026-06-30
- Version: 1.42.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.42.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.42.1

- **deprecated** — Deprecate strict parameter of pl.concat, replace with new how='horizontal_extend'
- **changed** — Add a sampled resolve mode for multi-file parquet metadata
- **changed** — Speed up small dtype series sums with a upcast sum kernel
- **changed** — Don't block on path expansion
- **fixed** — Fix incorrect sorted fast-path returning nan for grouped max
- **fixed** — Fix panic on scan_parquet filter of fixed-size binary column
- **fixed** — Fix decimal dynamic float cast
- **fixed** — Fix pyiceberg key dot HDFS prefix filter
- **fixed** — Fix projection pushdown panic on select(len()) after groupby
- **fixed** — Fully resolve remaining ResourceWarning leaks in database and iceberg tests
- **fixed** — Fix expiry time loading for AWS DeferredRefreshableCredentials
- **fixed** — Avoid panic on temporal extraction for datetime columns with nulls
- **fixed** — Prevent panic in replace when old or new contain Expr or object dtype values

##### ⚠️ Deprecations

- Deprecate `strict` parameter of `pl.concat`, replace with new `how='horizontal_extend'` (#27965)

##### 🚀 Performance improvements

- Add a sampled resolve mode for multi-file parquet metadata (#28111)
- Speed up small dtype series sums with a upcast sum kernel (#27958)
- Don't block on path expansion (#28073)

##### ✨ Enhancements

- Close ResourceWarning leaks in database tests (#28066)

##### 🐞 Bug fixes

- Incorrect sorted fast-path returning nan for grouped max (#28129)
- Fix panic on scan\_parquet filter of fixed-size binary column (#28122)
- Fix decimal dynamic float cast (#28126)
- Fix pyiceberg key dot HDFS prefix filter (#28109)
- Fix projection pushdown panic on `select(len())` after `groupby` (#28108)
- Fully resolve remaining `ResourceWarning` leaks in database/iceberg tests (#28107)
- Expiry time loading for AWS `DeferredRefreshableCredentials` (#28099)
- Close ResourceWarning leaks in database tests (#28066)
- Avoid panic on temporal extraction for datetime columns with nulls (#28054)
- Prevent panic in `replace` when `old`/`new` contain Expr or object dtype values (#27433)

##### 📖 Documentation

- Fix dataset regression in the examples (#28131)
- Emphasize to generally not ever write Rust tests (#28082)
- Mention Polars skill in User Guide's LLM section (#28113)

##### 🛠️ Other improvements

- Disallow usage of `tokio::spawn` in clippy (#28123)
- Improve `Makefile` with respect to `venv` robustness (#28110)
- Remove legacy prelude glob imports from leaf files (#28114)
- Skip pandas 3.0.4 due to `pd.TimeDelta` segfault (#28125)
- Update `mypy` to the new `2.x` release (#28116)
- Ensure `pyrefly` checks run as part of `make pre-commit` (#28095)
- Fix `test_select_explode_height_filter_order_by` failure when `POLARS_MAX_THREADS=2` (#28090)
- Add Morsel::height (#28060)

Thank you to all our contributors for making this release possible!
@0guban0v, @Kevin-Patyk, @TNieuwdorp, @alexander-beedie, @azimafroozeh, @dsprenkels, @kdn36, @nameexhaustion, @orlp, @raphaelroshan, @ritchie46 and @sar-cheng

### 1.42.0 — Python Polars 1.42.0

- Date: 2026-06-24
- Version: 1.42.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.42.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.42.0

- **deprecated** — Deprecate casts from string to temporal dtypes
- **changed** — Add bytes-based concurrency control for cloud IO
- **changed** — Stop flushing multiplexer on phase change
- **changed** — Prevent empty chunks from triggering copy in rechunk
- **changed** — Improve performance of struct unnest inside list eval on streaming
- **changed** — Eliminate filters with contradictory predicates
- **added** — Add naive out-of-core spilling to Polars
- **added** — Add experimental strict mode
- **changed** — Optimize non-negative len and null_count comparisons
- **changed** — Optimize len and null_count comparisons
- **added** — Support SQL's implicit JOIN syntax
- **added** — Add Expr.is_sorted
- **added** — Add suggestions in wrong api usage or mismatched column names
- **added** — Add external object_store support for non-native schemes
- **changed** — Skip Delta files and parquet row groups using per-field struct statistics
- **changed** — Improve IR sortedness detection for with_row_index and explode
- **added** — Add DataFrame.is_sorted()
- **added** — Expose fixed-size rolling window expressions in Python visitor
- **added** — Add tiered multi-file parquet metadata resolver
- **changed** — Cache and shuffle DNS for cloud object_store
- **deprecated** — Add a deprecation warning for .explode() without empty_as_null argument

##### ⚠️ Deprecations

- Deprecate casts from string to temporal dtypes (#28056)

##### 🚀 Performance improvements

- Add bytes-based concurrency control for cloud IO (#27924)
- Stop flushing multiplexer on phase change (#28013)
- Prevent empty chunks from triggering copy in rechunk (#27953)
- Improve performance of struct unnest inside list eval on streaming (#27905)
- Eliminate filters with contradictory predicates (#27775)

##### ✨ Enhancements

- Deprecate casts from string to temporal dtypes (#28056)
- Add naive out-of-core spilling to Polars (#27998)
- Add experimental strict mode (#28023)
- Optimize non-negative len and null\_count comparisons (#28002)
- Optimize len and null\_count comparisons (#27727)
- Support SQL's implicit `JOIN` syntax (#27890)
- Add `Expr.is_sorted` (#26708)
- Add suggestions in wrong api usage or mismatched column names (#27954)
- Add external object\_store support for non-native schemes (#27871)
- Skip Delta files and parquet row groups using per-field struct statistics (#27887)
- Improve IR sortedness detection for with\_row\_index and explode (#27875)
- Add `DataFrame.is_sorted()` (#27870)
- Expose fixed-size rolling window expressions in Python visitor (#27108)
- Fix SchemaError using lazy HConcat->Sink (#27770)
- Add tiered multi-file parquet metadata resolver (#27720)
- Cache and shuffle DNS for cloud object\_store (#27659)

##### 🐞 Bug fixes

- Add a deprecation warning for `.explode()` without `empty_as_null` argument (#28040)
- Fix `select(len())` incorrectly returned 0 when using `scan_iceberg` with `pyiceberg` as reader override (#28044)
- Ensure slice expr always observes input order (#28041)
- Fix projection pushdown with row index out of order (#28043)
- Fix cross-join predicates not applied when using `sink_*` functions (#28042)
- Grammar corrections (recommend to → recommend, allows to → allows using) (#28038)
- Ensure optimisations aren't omitted by cached IR nodes (#28004)
- Computed GROUP keys in SQL projections (#27989)
- Handle empty DataFrames in `dt.truncate` and `dt.round` (#26120)
- Address join alias state leakage in SQL CTEs (#27985)
- Support scanning `file://` URIs with percent-encoded paths (#27876)
- Lower SQL `[NOT] IN (subquery)` to semi/anti join (#27888)
- Check for continuity across morsels in AsOf join node (#27461)
- Add test for projection pushdown with hconcat regression (#27937)
- Traverse caches only once in explain (#27939)
- Preserve null placement when collapsing `sort.reverse()` into single sort (#27918)
- Incorrect schema order for hstack in projection pushdown optimizer (#27920)
- Fix duplicated map\_elements warning on streaming engine (#27919)
- Use block\_in\_place\_on for calls which can come from executor thread (#27855)
- Mismatch in max\_threads -> pipeline configuration (#27854)
- Keep maintain\_order on sliced unique (#27852)
- Fix SchemaError using lazy HConcat->Sink (#27770)
- Fix incorrect projection height when selecting only literals (#27825)
- Select with expr slice and len gave incorrect len (#27824)
- Prevent import panic when environment variable set to unexpected value (#27831)

##### 📖 Documentation

- New On-Prem release (#27979)
- Add note on OOM behavior on Kubernetes (#27972)
- Properly render backslashes in CSV `eol_char` docstrings (#27962)
- Add entry for `DataFrame.is_sorted()` (#27913)
- Clarify compat\_level export docs (#27715)
- Add robots.txt disallowing stale docs and added sitemap for better SEO (#27901)
- Update Polars \<> Spark comparison (#27873)
- Bump to patched version (#27851)
- Replace Typeform sign-up URL with new enterprise link (#27838)
- Correct wrong head call (#27848)
- Add Polars On-Prem 0.5.0 release (#27849)
- Correct onprem license helm values (#27847)
- Update connecting Polars Cloud to AWS documentation (#27823)
- Correct cost/connectivity sections (#27813)
- Add sections about egress (#27805)
- Tragic typo in On-Pre

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.42.0]_

### 1.41.2 — Python Polars 1.41.2

- Date: 2026-05-29
- Version: 1.41.2
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.41.2
- Permalink: https://whatsnew.fyi/product/polars/releases/1.41.2

- **changed** — Update to new jemalloc
- **changed** — Do not materialize ScalarColumn in Column split_at
- **changed** — Avoid materializing broadcast in array.shift
- **changed** — Avoid materializing broadcast list in list.sample(n) and list.sample(frac)
- **fixed** — Broken link to AI Policy corrected
- **changed** — Harden against async blocking deadlocks

##### 🚀 Performance improvements

- Update to new jemalloc (#27797)
- Do not materialize `ScalarColumn` in Column `split_at` (#27782)
- Avoid materializing broadcast in `array.shift` (#27740)
- Avoid materializing broadcast list in `list.sample(n)` and `list.sample(frac)` (#27679)

##### ✨ Enhancements

- Update to new jemalloc (#27797)

##### 🐞 Bug fixes

- Broken link to AI Policy corrected (#27793)
- Update to new jemalloc (#27797)

##### 📖 Documentation

- Update Polars On-Prem version stamp (#27799)
- Broken link to AI Policy corrected (#27793)
- Add release dates to the On-Prem releases page (#27787)
- Improve on-prem docs (#27788)
- Add query profiler video to On-Prem user guide (#27786)
- Add EKS/AKS/GKE guides (#27774)
- Add Polars On-Prem 0.4.2 (#27780)

##### 🛠️ Other improvements

- Run Pyrefly on `_utils` and `functions` (#27789)
- Harden against async blocking deadlocks (take 2) (#27767)

Thank you to all our contributors for making this release possible!
@ButteryPaws, @EndPositive, @Kevin-Patyk, @MarcoGorelli, @TNieuwdorp, @azimafroozeh, @carnarez, @kdn36, @lun3x, @orlp and @ritchie46

### 1.41.1 — Python Polars 1.41.1

- Date: 2026-05-27
- Version: 1.41.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.41.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.41.1

- **changed** — Improve performance of agg_n_unique with adaptive size dispatch to hashset or radix sort and capacity-aware reset
- **added** — Allow deeper expressions
- **fixed** — Raise length mismatch in multiple sort_by in group_by
- **fixed** — Respect min_samples for rolling_by ops with nulls
- **fixed** — Fix memory usage regression affecting TPCH Q22
- **added** — Add POLARS_ALLOW_NESTED_CSPE env var and make nested CSPE opt-in
- **fixed** — Post-apply residual pyarrow predicates
- **fixed** — Fix loss of precision for smaller floating types
- **fixed** — Fix filter at scan dropped in CSPE filter pushdown
- **fixed** — Fix portstate assertion error on is_in
- **fixed** — Fix incorrect when/then after forward fill / reverse in groupby
- **fixed** — Accept empty Thrift list encoded as bare 0x00 byte in parquet metadata
- **fixed** — Stabilize object store credentialprovider cache key

##### 🚀 Performance improvements

- Adaptive size dispatch to hashset or radix sort + capacity-aware reset in `agg_n_unique` (#27719)

##### ✨ Enhancements

- Allow deeper expressions (#27768)

##### 🐞 Bug fixes

- Raise length mismatch in multiple `sort_by` in `group_by` (#27772)
- Respect min\_samples for rolling\_by ops with nulls (#27706)
- Fix memory usage regression affecting TPCH Q22 (#27758)
- Add `POLARS_ALLOW_NESTED_CSPE` env var and make nested CSPE opt-in (#27765)
- Post-apply residual pyarrow predicates (#27764)
- Fix loss of precision for smaller floating types(#27662) (#27732)
- Filter at scan dropped in CSPE filter pushdown (#27763)
- Fix portstate assertion error on is\_in (#27757)
- Fix incorrect when/then after forward fill / reverse in groupby (#27745)
- Accept empty Thrift list encoded as bare 0x00 byte in parquet metadata (#27754)
- Stabilize object store `credentialprovider` cache key (#27712)
- Add to `merge_sorted` docs that the input must be nulls first (#27743)

##### 📖 Documentation

- Docs fixes (#27766)
- Sync from Polars Cloud (#27751)
- Add to `merge_sorted` docs that the input must be nulls first (#27743)

##### 🛠️ Other improvements

- Attribute annotations for `CatalogCredentialProvider` (#27739)
- Solve `type: ignore` in \_AioDataFrameResult (#27311)
- Remove dead code in `_write_utils.py` (#27721)
- Remove unnecessary ``not isinstance(v, DataType)`` check (#27723)

Thank you to all our contributors for making this release possible!
@EndPositive, @JakubValtar, @MarcoGorelli, @NicoOhR, @azimafroozeh, @carnarez, @dsprenkels, @jorenham, @kdn36, @nameexhaustion, @orlp and @ritchie46

### 1.41.0 — Python Polars 1.41.0

- Date: 2026-05-22
- Version: 1.41.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.41.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.41.0

- **added** — Add LazyFrame.gather
- **added** — Add Expr.is_empty
- **added** — Add support for the SQL FILTER clause for aggregate functions, and STRING_AGG
- **added** — Add null_on_oob in {Expr/Series}.gather
- **added** — Add Rust backend for Expr.has_nulls
- **added** — Add streaming GatherNode
- **changed** — Stabilize streaming engine
- **changed** — Stabilize float16
- **changed** — Use true division for the / operator in Polars SQL
- **changed** — Dispatch {list,arr}.{unique,n_unique,reverse} to group_by engine
- **changed** — Speed up parquet metadata decode with hand-written Thrift
- **fixed** — Panic in scan of empty IPC with slice
- **fixed** — Persist object_store rebuild state in cache
- **fixed** — Sort flag on GroupsType only applies to first element
- **fixed** — Don't unwrap channel send in streaming join_asof
- **fixed** — Fix merge_sorted panic when List in frame
- **fixed** — Raise TypeError when calling next() directly on GroupBy objects
- **fixed** — Data type comparison for extension types
- **fixed** — Prevent panic when switching from one extension dtype to another
- **deprecated** — Deprecate the StringCache

##### 🏆 Highlights

- Add LazyFrame.gather (#27501)
- Nested common subplan elimination (#27340)
- Stabilize streaming engine (#27497)
- Speed up parquet metadata decode with hand-written Thrift (#27427)

##### ⚠️ Deprecations

- Deprecate the StringCache (#27580)

##### 🚀 Performance improvements

- Dispatch `{list,arr}.{unique,n_unique,reverse}` to group\_by engine (#27278)
- Improve in-memory grouped non-null count (#27702)
- Factor shared conjuncts out of OR-of-ANDs predicates (#27627)
- Skip downloading IPC batches exceeding slice bounds (#27683)
- Avoid materializing broadcast list in `list.shift` (#27628)
- Optimise `json_decode` Datetime string parsing (#27559)
- Speed up `to_numpy` C-order via cache-blocked transpose (#27522)
- Optimize `select(len())` for non-strict horizontal concat (#27516)
- Pushdown slices to inputs on left/right/full join (#27508)
- Don't infer CSV schema if schema is set (#27507)
- Nested common subplan elimination (#27340)
- Make `is_in` row-group pruning precise on null-containing haystacks (#27495)
- Don't do fused-multiply-add on scalars (#27479)
- List full fast path (#27477)
- Make `is_in` row-group pruning precise on multi-value lists (#27475)
- Add streaming GatherNode (#27465)
- Lower non-elementwise FunctionExprIR to ColumnarFunctionNode (#27462)
- Speed up parquet metadata decode with hand-written Thrift (#27427)

##### ✨ Enhancements

- Use true division for the `/` operator in Polars SQL (#27391)
- Add Rust backend for Expr.has\_nulls (#27590)
- Stabilize float16 (#27607)
- Add Expr.is\_empty (#27583)
- Add support for the SQL `FILTER` clause for aggregate functions, and `STRING_AGG` (#27564)
- Make parquet `FileMetadata` prunable for IR-plan dispatch (#27535)
- Broadcast scalar input for `list.slice` (#27487)
- Add LazyFrame.gather (#27501)
- Add `null_on_oob` in {Expr/Series}.gather (#27327)
- Stabilize streaming engine (#27497)
- Process batched `arr.eval` on overflow boundaries (#27496)
- Process batched `list.eval` on overflow boundaries (#27483)
- Print `SLICED UNION` in LazyFrame explain (#27467)

##### 🐞 Bug fixes

- Panic in scan of empty IPC with slice (#27708)
- Persist object\_store rebuild state in cache (#27707)
- Sort flag on GroupsType only applies to first element (#27684)
- Invalid unwrap\_unchecked when length isn't exact (#27685)
- Don't unwrap channel send in streaming join\_asof (#27688)
- Fix `merge_sorted` panic when List in frame (#27568)
- Put AsOf join buffered Morsels back the front of the deque if we cannot process them rn (#27658)
- Fix skip\_batches logic for NaN (#27673)
- Raise `TypeError` when calling `next()` directly on `GroupBy` objects (#27562)
- Data type comparison for extension types (#27632)
- Share last-morsel split budget across files in streaming multi-scan (#27630)
- Bytes scalars were not being broadcast in dataframe constructor (#27621)
- Reset the sort-options in `Series::is_sorted()` after row-encoding columns (#27614)
- Rayon deadlock with re-entrant io sources (#27600)
- Don't push negative-offset slices through `HConcat` (#27570)
- Logic error in streaming is\_empty (#27602)
- Fix incorrect CSE with large is\_in literal (#27575)
- AnonymousFunction can qualify as SQL aggregator (#26986)
- Fix CSPE panic in cloud (#27594)
- Set merge-join streaming node to `Finished` if its sending port is `Done` (#27572)
- Widen decimal precision on sum aggregation at runtime (#27579)
- Fix `str.to_time` was raising unnecessarily when input was all nulls (#27574)
- Prevent panic when switching from one extension dtype to another (#27566)
- Fix `DataFrame.write_database(..., if_table_exists="append", engine="adbc")` not handling missing tables correctly (#26913)
- Ensure `json_decode` doesn't fail for Date and Time string deserialization (#27554)
- Incorrect RUSTFLAGS passing in Makefile (#27555)
- Fix panic on reading IPC with 0-row compressed bitmap (#27551)
- Set HEAD\_RESPONSE\_SIZE\_ESTIMATE to 0 (#27548)
- Fix lazy concat horizontal didn'

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.41.0]_

### 1.40.1 — Python Polars 1.40.1

- Date: 2026-04-22
- Version: 1.40.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.40.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.40.1

- **changed** — Skip validity mask processing in __array_ufunc__ when no inputs have nulls
- **added** — Add maintain_order parameter to merge_sorted
- **fixed** — Honor having predicate in GroupBy iter
- **fixed** — Use the physical dtype for NumUnorderedImplodeReducer arrow ListArray
- **fixed** — Address bug in reduce_balanced for certain input length lists affecting pl.concat
- **fixed** — Ensure list.sample() allows fraction > 1 when with_replacement=True
- **fixed** — Ensure append() errors when upcast=False
- **fixed** — Always rechunk sorts, prune sorts even in eager execution
- **fixed** — Fix typing for DataFrame.__init__ and Series.__init__ so they don't require all optional dependencies to be installed

##### 🚀 Performance improvements

- Skip validity mask processing in \_\_array\_ufunc\_\_ when no inputs have nulls (#27358)

##### ✨ Enhancements

- Cargo deny (#27363)
- Add `maintain_order` parameter to `merge_sorted` (#27263)

##### 🐞 Bug fixes

- Honor `having` predicate in `GroupBy` iter (#27370)
- Use the physical dtype for `NumUnorderedImplodeReducer` arrow `ListArray` (#27375)
- Address bug in `reduce_balanced` for certain input length lists affecting `pl.concat` (#27352)
- Ensure `list.sample()` allows `fraction` > 1 when `with_replacement=True` (#27350)
- Ensure `append()` errors when `upcast=False` (#27346)
- Always rechunk sorts, prune sorts even in eager execution (#27356)
- Fix typing for `DataFrame.__init__` and `Series.__init__` so they don't require all optional dependencies to be installed (#27348)

##### 📖 Documentation

- Split out openlineage docs into guide and configuration (#27371)
- Add explanation on the observatory sqlite db file (#27354)

##### 🛠️ Other improvements

- Disable mypy type checking for `pyarrow` calls (#27377)
- Disable debug symbols in macos coverage tests (#27361)
- Cargo deny (#27363)

Thank you to all our contributors for making this release possible!
@EndPositive, @Kevin-Patyk, @MarcoGorelli, @carnarez, @dsprenkels, @gab23r, @jonathanchang31, @kdn36, @mzjp2 and @ritchie46

### 1.40.0 — Python Polars 1.40.0

- Date: 2026-04-18
- Version: 1.40.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.40.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.40.0

- **added** — Add streaming support for grouped AsOf join
- **added** — Add `ignore_nulls` to `{list,arr}.{any,all}`
- **added** — Add `is_unique` to list/array dtypes
- **added** — Add `pl.merge_sorted` operating on multiple frames
- **added** — Add native streaming `interpolate`
- **changed** — Create IR slice from expr slice pushdown
- **changed** — Avoid unnecessary rechunk when sorting already sorted DataFrame
- **changed** — Lower basic over() to streaming primitives
- **changed** — Lower `drop_{nulls,nans}` in streaming `group_by` aggregations
- **changed** — Lower `entropy` to streaming reductions
- **changed** — Streaming `strptime` with `format=None`
- **changed** — Lower `skew` / `kurtosis` to streaming aggregations
- **changed** — Post apply pyarrow filter in Polars' engine instead of pyarrow
- **changed** — Optimize `drop_nulls().{first,last}()` to `{first,last}(ignore_nulls=True)`
- **changed** — Always process pyarrow scan in batches
- **changed** — Make `cut` output `Enum` and mark as elementwise
- **changed** — Use delta stats for mixed hive and non-hive predicate pushdown
- **changed** — Take into account size per row in join sampling
- **changed** — Streaming is_first_distinct and unique(maintain_order=True)
- **changed** — Streaming `cov` and `corr`

##### 🏆 Highlights

- Add streaming support for grouped AsOf join (#27293)

##### ⚠️ Deprecations

- Deprecate support for dataframe interchange protocol (#27214)

##### 🚀 Performance improvements

- Create IR slice from expr slice pushdown (#27200)
- Add streaming support for grouped AsOf join (#27293)
- Avoid unnecessary rechunk when sorting already sorted DataFrame (#27264)
- Lower basic over() to streaming primitives (#27303)
- Lower `drop_{nulls,nans}` in streaming `group_by` aggregations (#27296)
- Lower `entropy` to streaming reductions (#27174)
- Add native streaming `interpolate` (#27185)
- Streaming `strptime` with `format=None` (#27056)
- Lower `skew` / `kurtosis` to streaming aggregations (#27176)
- Post apply pyarrow filter in Polars' engine instead of pyarrow (#27192)
- Optimize `drop_nulls().{first,last}()` to `{first,last}(ignore_nulls=True)` (#27187)
- Always process pyarrow scan in batches (#27183)
- Make `cut` output `Enum` and mark as elementwise (#27173)
- Remove unused expression sorts (#27075)
- Use delta stats for mixed hive and non-hive predicate pushdown (#27102)
- Take into account size per row in join sampling (#27098)
- Streaming is\_first\_distinct and unique(maintain\_order=True) (#27052)
- Streaming `cov` and `corr` (#27008)
- Add sorted unique node to streaming engine (#26990)
- Ensure Expr.append is lowered in streaming engine (#27022)
- Collapse consecutive Sort nodes (#26965)
- Drop `maintain_order=True` requirement in `sink_delta` (#27007)

##### ✨ Enhancements

- Add `ignore_nulls` to `{list,arr}.{any,all}` (#27186)
- Lock-free memory manager with spill-to-disk and fully OOC multiplexer (#26774)
- Add `is_unique` to list/array dtypes (#27290)
- Streaming pyarrow datasets sources (#27230)
- Add `pl.merge_sorted` operating on multiple frames (#27014)
- Allow `group_by()` without key exprs (#27141)
- Change default scan/read\_lines column name from "lines" to "line" (#27122)
- Make unnest() effective on all columns by default (#27029)
- Collapse consecutive Sort nodes (#26965)

##### 🐞 Bug fixes

- Update `groups` to correct length for `Implode` (#27282)
- Fix scan\_csv missing\_columns='insert' overwrote existing data with NULLs (#27297)
- Raise on non-numeric inputs in `pl.int_ranges` (#27294)
- Fix always-true filter conversion to Iceberg filter (#27119)
- Do not skip nulls when enumerating over rows in grouped AsOf join (#27275)
- Fix `pivot` dropping data for null `on` values (#27273)
- Resolve multiple files deadlock in CSV async reader (#27073)
- Widen decimal precision on sum aggregation (#27270)
- Correct lf.remote type (#27261)
- Default `LazyFrame.map_batches` to no optimizations (#27262)
- Extend `StructEval` schema context in `StackOptimizer` (#27243)
- Preserve nulls when casting from all-null `Series` to `Struct` (#27241)
- Fix `scan_delta` filter on empty dataframe (#27244)
- Prevent `DataFrame` creation panic on `list[struct]` with heterogenous types (#27217)
- Named aggregation `__structify` was being ignored (#27148)
- Skip `null` group entries when collecting AsOf-by groups (#27215)
- Fix panic with empty order\_by in over expression (#27088)
- Write field ID from `sink_parquet` (#27196)
- Fix statistics for Null columns in Parquet (#27021)
- Do not prune sort nodes containing slice with dyn predicate (#27140)
- Correct grouped `Binary` `arg_min`/`arg_max` and `String` single-element arg indices (#27172)
- Resolve multiple files deadlock in NDJSON async reader (#27204)
- Overflow panic in interpolate nearest (#27205)
- Using checked arithmetic in `int96_to_i64_ns` to prevent overflow panic (#27129)
- Don't trigger csv fast count if predicate is pushed down (#27190)
- Support all integer dtypes for Series index assignment (#27188)
- Streaming sort by-expressions were lowered incorrectly (#27158)
- Replace multiprocessing.dummy.Pool with ThreadPoolExecutor (#27175)
- Reset IO metrics instead of consuming (#27156)
- Output SVG if output\_path ends with '.svg' in show\_grap

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.40.0]_

### 1.39.3 — Python Polars 1.39.3

- Date: 2026-03-20
- Version: 1.39.3
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.39.3
- Permalink: https://whatsnew.fyi/product/polars/releases/1.39.3

* No changes

Thank you to all our contributors for making this release possible!
@ritchie46

### 1.39.2 — Python Polars 1.39.2

- Date: 2026-03-17
- Version: 1.39.2
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.39.2
- Permalink: https://whatsnew.fyi/product/polars/releases/1.39.2

* No changes

Thank you to all our contributors for making this release possible!
@nameexhaustion and @ritchie46

### 1.39.1 — Python Polars 1.39.1

- Date: 2026-03-17
- Version: 1.39.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.39.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.39.1

- **fixed** — Handle empty rolling windows in streaming engine

##### 🐞 Bug fixes

- Handle empty rolling windows in streaming engine (#26903)

##### 📖 Documentation

- Add documentation for on\_columns for LazyFrame pivot (#26859)

##### 🛠️ Other improvements

- Bump build deps used in ARM64 Windows release pipeline (#26892)

Thank you to all our contributors for making this release possible!
@Kevin-Patyk, @RenzoMXD, @TNieuwdorp, @dsprenkels, @gautamvarmadatla, @nameexhaustion, @nicholaslegrand102 and @ritchie46

### 1.39.0 — Python Polars 1.39.0

- Date: 2026-03-12
- Version: 1.39.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.39.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.39.0

- **changed** — Lower arg_{min,max} to streaming engine
- **changed** — Additional IR slice pushdown after filter pushdown
- **changed** — Streaming first/last on Enum through physical
- **changed** — Fast filter for scalar predicates
- **changed** — Allow SimpleProjection in streaming engine to rename
- **changed** — Streaming cloud download for scan_csv
- **changed** — Drop columns only needed for predicates after the predicate is applied
- **changed** — Run projection pushdown after predicate pushdown
- **changed** — Comparison literal downcasting
- **changed** — Add dynamic predicates for TopK
- **changed** — Increase minimum default parquet row group prefetch to 8
- **changed** — Partial predicate conversion to PyArrow
- **changed** — Streaming cloud download for scan_ndjson and scan_lines
- **changed** — Improve CSV and NDJSON cloud sink performance
- **changed** — Tune cloud writer performance
- **changed** — Allow parallel InMemorySinks in streaming engine
- **added** — Support Expr for holidays in business day calculations
- **added** — Parameter for pivot to always include value column name
- **added** — Extend Expr.reinterpret to all numeric types of the same size
- **added** — Add missing_columns parameter to scan_csv

##### 🚀 Performance improvements

- Lower `arg_{min,max}` to streaming engine (#26845)
- Additional IR slice pushdown after filter pushdown (#26815)
- Streaming first/last on Enum through physical (#26783)
- Fast filter for scalar predicates (#26745)
- Allow SimpleProjection in streaming engine to rename (#26709)
- Streaming cloud download for `scan_csv` (#26637)
- Drop columns only needed for predicates after the predicate is applied (#26703)
- Run projection pushdown after predicate pushdown (#26688)
- Comparison literal downcasting (#26663)
- Add dynamic predicates for TopK (#26495)
- Increase minimum default parquet row group prefetch to 8 (#26632)
- Partial predicate conversion to PyArrow (#26567)
- Streaming cloud download for `scan_ndjson` / `scan_lines` (#26563)
- Grab GIL fewer times during Object join materialization (#26587)
- Improve CSV and NDJSON cloud sink performance (#26545)
- Tune cloud writer performance (#26518)
- Allow parallel InMemorySinks in streaming engine (#26501)
- Add streaming `AsOf` join node (#26398)
- Don't always rechunk on gather of nested types (#26478)

##### ✨ Enhancements

- Support Expr for holidays in business day calculations (#26193)
- Parameter for pivot to always include value column name (#26730)
- Raise error in `.collect_schema()` when `arr.get()` is out-of-bounds (#26866)
- Extend `Expr.reinterpret` to all numeric types of the same size (#26401)
- Add missing\_columns parameter to scan\_csv (#26787)
- Clear no-op scan projections (#26858)
- Support nested datatypes for `{min,max}_by` (#26849)
- Support SQL `ARRAY` init from typed literals (#26622)
- Accept table identifier string in `scan_iceberg()` (#26826)
- Add a convenience `make fresh` command to the Makefile (#26809)
- Expose "use\_zip64" Workbook option for `write_excel` (#26699)
- Add unstable `LazyFrame.sink_iceberg` (#26799)
- Add maintain order argument on implode (#26782)
- Speed up casting primitive to bool by at least 2x (#26823)
- Support ASCII format table input to `pl.from_repr` (#26806)
- Enable rowgroup skipping for float columns (#26805)
- Add expression context to errors (#26716)
- Add Decimal support for product reduction (#26725)
- Support all Iceberg V2 arrow types in sink\_parquet arrow\_schema parameter (#26669)
- Re-work behavior of arrow\_schema parameter on sink\_parquet (#26621)
- Add `contains_dtype()` method for `Schema` (#26661)
- Implement `truncate` as a "to\_zero" rounding mode (#26677)
- More generic streaming GroupBy lowering (#26696)
- Create an `Alignment` TypeAlias (#26668)
- Add basic MemoryManager to track buffered dataframes for out-of-core support later (#26443)
- Add `truncate` Expression for numeric values (#26666)
- Better error messages for hex literal conversion issues in the SQL interface (#26657)
- Add SQL support for `LPAD` and `RPAD` string functions (#26631)
- Support SQL "FROM-first" `SELECT` query syntax (#26598)
- Improve `base_type` typing (#26602)
- Bump Chrono to 0.4.24, enabling stricter parsing of `%.3f`/`%.6f`/`%.9f` specifiers (#26075)
- Expose unstable `assert_schema_equal` in py-polars (#24869)
- Allow parsing of compact ISO 8601 strings (#24629)
- Add optional "label" param to DataFrame `corr` (#26588)
- Streaming cloud download for `scan_ndjson` / `scan_lines` (#26563)
- Configuration to cast integers to floats in `cast_options` for `scan_parquet` (#26492)
- Add escaping to quotes and newlines when reading JSON object into string (#26578)
- Standardise on RFC-5545 when doing datetime arithmetic on timezone-aware datetimes (#26425)
- Support `sas_token` in Azure credential provider (#26565)
- Relax SQL requirement for derived tables and subqueries to have aliases (#26543)
- Add polars-config and pl.Config.reload\_env\_vars() (#26524)
- Record path for object store error raised from sinks (#26541)
- Use CRC64NVME for checksum in aws sinks (#26522)
- Add `get()` for binary Series (#26514)
- Add streaming `AsOf` join node (#26398)
- Add primitive filter -> agg low

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.39.0]_

### 1.38.1 — Python Polars 1.38.1

- Date: 2026-02-06
- Version: 1.38.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.38.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.38.1

- **added** — Add get() to retrieve a byte from binary data
- **changed** — Remove with_context in SQL lowering
- **fixed** — Do not overwrite used names in cluster_with_columns pushdown
- **fixed** — Do not mark output of concat_str on multiple inputs as sorted
- **fixed** — Fix CSV schema inference content line duplication bug
- **fixed** — Fix InvalidOperationError using scan_delta with filter
- **fixed** — Alias giving missing column after streaming GroupBy CSE
- **fixed** — Ensure by_name selector selects only names
- **fixed** — Restore compatibility of strings written to parquet with pyarrow filter
- **fixed** — Update schema in cluster_with_columns optimization
- **fixed** — Fix negative slice in groups slicing
- **fixed** — Don't run CPU check on aarch64 musl
- **fixed** — Fixed annotations shadowed by class methods
- **fixed** — Fix selector match patterns for multiline column names

##### ✨ Enhancements

- Add get() to retrieve a byte from binary data (#26454)
- Remove with\_context in SQL lowering (#26416)

##### 🐞 Bug fixes

- Do not overwrite used names in cluster\_with\_columns pushdown (#26467)
- Do not mark output of concat\_str on multiple inputs as sorted (#26468)
- Fix CSV schema inference content line duplication bug (#26452)
- Fix InvalidOperationError using `scan_delta` with filter (#26448)
- Alias giving missing column after streaming GroupBy CSE (#26447)
- Ensure `by_name` selector selects only names (#26437)
- Restore compatibility of strings written to parquet with pyarrow filter (#26436)
- Update schema in cluster\_with\_columns optimization (#26430)
- Fix negative slice in groups slicing (#26442)
- Don't run CPU check on aarch64 musl (#26439)
- Fixed annotations shadowed by class methods (#26356)
- Remove the `POLARS_IDEAL_MORSEL_SIZE` monkeypatching in the parametric merge-join test (#26418)
- Fix `selector` match patterns for multiline column names (#26320)

##### 📖 Documentation

- Add `sink_delta` to API reference (#26446)

##### 🛠️ Other improvements

- Cleanup unused attributes in optimizer (#26464)
- Use `Expr::Display` as catch all for IR - DSL asymmetry (#26471)
- Ignore pytz in mypy (#26441)
- Remove the `POLARS_IDEAL_MORSEL_SIZE` monkeypatching in the parametric merge-join test (#26418)
- Cleanup the parametric merge-join test (#26413)

Thank you to all our contributors for making this release possible!
@Voultapher, @alexander-beedie, @azimafroozeh, @cmdlineluser, @dependabot[bot], @dsprenkels, @hamdanal, @kdn36, @nameexhaustion, @orlp, @ritchie46 and [dependabot[bot]](https://github.com/apps/dependabot)

### 1.38.0 — Python Polars 1.38.0

- Date: 2026-02-04
- Version: 1.38.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.38.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.38.0

- **deprecated** — Deprecate retries=n in favor of storage_options={"max_retries": n}
- **changed** — Enable zero-copy object_store put upload for IPC sink
- **changed** — Resolve file schema's and metadata concurrently
- **changed** — Run elementwise CSEE for the streaming engine
- **changed** — Disable morsel splitting for fast-count on streaming engine
- **changed** — Implement streaming decompression for scan_ndjson and scan_lines
- **changed** — Improve string slicing performance
- **changed** — Refactor scan_delta to use python dataset interface
- **changed** — Add dedicated kernel for group-by arg_max/arg_min
- **added** — Add streaming merge-join
- **changed** — Generalize Bitmap::new_zeroed opt for Buffer::zeroed
- **changed** — Reduce fs stat calls in path expansion
- **changed** — Lower streaming group_by n_unique to unique().len()
- **fixed** — Avoid OOM for scan_ndjson and scan_lines if input is compressed and negative slice
- **added** — Support anonymous agg in-mem
- **added** — Add unstable arrow_schema parameter to sink_parquet
- **added** — Allow quantile to compute multiple quantiles at once
- **added** — Allow empty LazyFrame in LazyFrame.group_by(...).map_groups
- **added** — Add scan_lines
- **added** — Support regex in str.split
- **added** — Add nulls support for all rolling_by operations

##### ⚠️ Deprecations

- Deprecate `retries=n` in favor of `storage_options={"max_retries": n}` (#26155)

##### 🚀 Performance improvements

- Enable zero-copy object\_store `put` upload for IPC sink (#26288)
- Resolve file schema's and metadata concurrently (#26325)
- Run elementwise CSEE for the streaming engine (#26278)
- Disable morsel splitting for fast-count on streaming engine (#26245)
- Implement streaming decompression for scan\_ndjson and scan\_lines (#26200)
- Improve string slicing performance (#26206)
- Refactor `scan_delta` to use python dataset interface (#26190)
- Add dedicated kernel for group-by `arg_max/arg_min` (#26093)
- Add streaming merge-join (#25964)
- Generalize Bitmap::new\_zeroed opt for Buffer::zeroed (#26142)
- Reduce fs stat calls in path expansion (#26173)
- Lower streaming group\_by n\_unique to unique().len() (#26109)

##### ✨ Enhancements

- Avoid OOM for scan\_ndjson and scan\_lines if input is compressed and negative slice (#26396)
- Support annoymous agg in-mem (#26376)
- Add unstable `arrow_schema` parameter to `sink_parquet` (#26323)
- Improve error message formatting for structs (#26349)
- Remove parquet field overwrites (#26236)
- Enable zero-copy object\_store `put` upload for IPC sink (#26288)
- Improved disambiguation for qualified wildcard columns in SQL projections (#26301)
- Expose `upload_concurrency` through env var (#26263)
- Allow quantile to compute multiple quantiles at once (#25516)
- Allow empty LazyFrame in `LazyFrame.group_by(...).map_groups` (#26275)
- Use delta file statistics for batch predicate pushdown (#26242)
- Add streaming UnorderedUnion (#26240)
- Implement compression support for sink\_ndjson (#26212)
- Add unstable record batch statistics flags to `{sink/scan}_ipc` (#26254)
- Support CSE for python UDFs on the same address (#26253)
- Cloud retry/backoff configuration via `storage_options` (#26204)
- Use same sort order for expanded paths across local / cloud / directory / glob (#26191)
- Add streaming merge-join (#25964)
- Serialize optimization flags for cloud plan (#26168)
- Add compression support to write\_csv and sink\_csv (#26111)
- Add `scan_lines` (#26112)
- Support regex in `str.split` (#26060)
- Add unstable IPC Statistics read/write to `scan_ipc`/`sink_ipc` (#26079)
- Add unstable `height` parameter to `DataFrame`/`LazyFrame` (#26014)
- Remove old partition sink API (#26100)
- Expose ArrowStreamExportable on python collect batches iterator (#26074)
- Add nulls support for all rolling\_by operations (#26081)

##### 🐞 Bug fixes

- Correct off-by-one in RLE row counting for nullable dictionary-encoded columns (#26411)
- Support very large integers in env var limits (#26399)
- Fix PlPath panic from incorrect slicing of UTF8 boundaries (#26389)
- Fix Float dtype for spearman correlation (#26392)
- Fix optimizer panic in right joins with type coercion (#26365)
- Don't serialize retry config from local environment vars (#26289)
- Fix `PartitionBy` with scalar key expressions and `diff()` (#26370)
- Add {Float16, Float32} -> Float32 lossless upcast (#26373)
- Fix panic using `with_columns` and `collect_all` (#26366)
- Add multi-page support for writing dictionary-encoded Parquet columns (#26360)
- Ensure slice advancement when skipping non-inlinable values in `is_in` with inlinable needles (#26361)
- Pin `xlsx2csv` version temporarily (#26352)
- Bugs in ViewArray total\_bytes\_len (#26328)
- Overflow in i128::abs in Decimal fits check (#26341)
- Make Expr.hash on Categorical mapping-independent (#26340)
- Clone shared GroupBy node before mutation in physical plan creation (#26327)
- Fixed "sheet\_name" typing for `read_ods` and `read_excel` (#26317)
- Improve Polars dtype inference from Python `Union` typing (#26303)
- Consider the "current location" of an item when computing `rolling_rank_by` (#26287)
- Reset `is_count_star` flag between queries in collect\_all (#26256)
- Fix incorrect is\_between filter on scan\_parquet (#26284)
- Make polars compatibl

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.38.0]_

### 1.37.1 — Python Polars 1.37.1

- Date: 2026-01-12
- Version: 1.37.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.37.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.37.1

- **changed** — Speed up SQL interface UNION clauses
- **fixed** — Optimize slicing support on compressed IPC
- **fixed** — CPU check for musl builds
- **fixed** — Propagate C Stream import errors instead of panicking
- **fixed** — Fix slicing on compressed IPC

##### 🚀 Performance improvements

- Speed up `SQL` interface "UNION" clauses (#26039)

##### 🐞 Bug fixes

- Optimize slicing support on compressed IPC (#26071)
- CPU check for musl builds (#26076)
- Propagate C Stream import errors instead of panicking (#26036)
- Fix slicing on compressed IPC (#26066)

##### 📖 Documentation

- Clarify min\_by/max\_by behavior on ties (#26077)

##### 🛠️ Other improvements

- Mark top slow normal tests as slow (#26080)
- Update breaking deps (#26055)
- Fix for upstream url bug and update deps (#26052)
- Properly pin chrono (#26051)
- Don't run rust doctests (#26046)
- Update deps (#26042)
- Ignore very slow test (#26041)

Thank you to all our contributors for making this release possible!
@Voultapher, @alexander-beedie, @kdn36, @nameexhaustion, @orlp, @ritchie46 and @wtn

### 1.37.0 — Python Polars 1.37.0

- Date: 2026-01-10
- Version: 1.37.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.37.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.37.0

- **added** — Add new pl.PartitionBy API
- **added** — Add lazy collect_all
- **added** — Add nulls support for rolling_mean_by
- **added** — Expose record batch size in {sink,write}_ipc
- **added** — Add null_on_oob parameter to expr.get
- **added** — Support streaming IPC scan from S3 object store
- **added** — Add pl.Expr.(min|max)_by
- **added** — Add Series sql method for API consistency
- **added** — Support Binary and Decimal in arg_(min|max)
- **added** — Add missing Series.arr.mean
- **changed** — Speed up SQL interface ORDER BY clauses
- **changed** — Add fast kernel for is_nan and use it for numpy NaN->null conversion
- **changed** — New streaming NDJSON sink pipeline
- **changed** — New streaming CSV sink pipeline
- **changed** — Replace ryu with faster zmij
- **changed** — Use new sink pipeline for write/sink_ipc
- **changed** — Improve handling of unqualified SQL JOIN columns that are ambiguous
- **changed** — Drop Python 3.9 support
- **fixed** — Make struct.with_fields data model coherent
- **fixed** — Ensure chunk consistency in in-memory join

##### 🚀 Performance improvements

- Speed up `SQL` interface "ORDER BY" clauses (#26037)
- Add fast kernel for is\_nan and use it for numpy NaN->null conversion (#26034)
- Optimize ArrayFromIter implementations for ObjectArray (#25712)
- New streaming NDJSON sink pipeline (#25948)
- New streaming CSV sink pipeline (#25900)
- Dispatch partitioned usage of `sink_*` functions to new-streaming by default (#25910)
- Replace ryu with faster zmij (#25885)
- Reduce memory usage for .item() count in grouped first/last (#25787)
- Skip schema inference if schema provided for `scan_csv/ndjson` (#25757)
- Add width-aware chunking to prevent degradation with wide data (#25764)
- Use new sink pipeline for write/sink\_ipc (#25746)
- Reduce memory usage when scanning multiple parquet files in streaming (#25747)
- Don't call cluster\_with\_columns optimization if not needed (#25724)

##### ✨ Enhancements

- Add new `pl.PartitionBy` API (#26004)
- ArrowStreamExportable and sink\_delta (#25994)
- Release musl builds (#25894)
- Implement streaming decompression for CSV `COUNT(*)` fast path (#25988)
- Add nulls support for rolling\_mean\_by (#25917)
- Add lazy `collect_all` (#25991)
- Add streaming decompression for NDJSON schema inference (#25992)
- Improved handling of unqualified SQL `JOIN` columns that are ambiguous (#25761)
- Drop Python 3.9 support (#25984)
- Expose record batch size in `{sink,write}_ipc` (#25958)
- Add `null_on_oob` parameter to `expr.get` (#25957)
- Suggest correct timezone if timezone validation fails (#25937)
- Support streaming IPC scan from S3 object store (#25868)
- Implement streaming CSV schema inference (#25911)
- Support hashing of meta expressions (#25916)
- Improve `SQLContext` recognition of possible table objects in the Python globals (#25749)
- Add pl.Expr.(min|max)\_by (#25905)
- Improve MemSlice Debug impl (#25913)
- Implement or fix json encode/decode for (U)Int128, Categorical, Enum, Decimal (#25896)
- Expand scatter to more dtypes (#25874)
- Implement streaming CSV decompression (#25842)
- Add Series `sql` method for API consistency (#25792)
- Mark Polars as safe for free-threading (#25677)
- Support Binary and Decimal in arg\_(min|max) (#25839)
- Allow Decimal parsing in str.json\_decode (#25797)
- Add `shift` support for Object data type (#25769)
- Add missing `Series.arr.mean` (#25774)
- Allow scientific notation when parsing Decimals (#25711)

##### 🐞 Bug fixes

- Release GIL on collect\_batches (#26033)
- Missing buffer update in String is\_in Parquet pushdown (#26019)
- Make `struct.with_fields` data model coherent (#25610)
- Incorrect output order for order sensitive operations after join\_asof (#25990)
- Use SeriesExport for pyo3-polars FFI (#26000)
- Add pl.Schema to type signature for DataFrame.cast (#25983)
- Don't write Parquet min/max statistics for i128 (#25986)
- Ensure chunk consistency in in-memory join (#25979)
- Fix varying block metadata length in IPC reader (#25975)
- Implement collect\_batches properly in Rust (#25918)
- Fix panic on arithmetic with bools in list (#25898)
- Convert to index type with strict cast in some places (#25912)
- Empty dataframe in streaming non-strict hconcat (#25903)
- Infer large u64 in json as i128 (#25904)
- Set http client timeouts to 10 minutes (#25902)
- Correct lexicographic ordering for Parquet BYTE\_ARRAY statistics (#25886)
- Raise error on duplicate `group_by` names in `upsample()` (#25811)
- Correctly export view buffer sizes nested in Extension types (#25853)
- Fix `DataFrame.estimated_size` not handling overlapping chunks correctly (#25775)
- Ensure Kahan sum does not introduce NaN from infinities (#25850)
- Trim excess bytes in parquet decode (#25829)
- Fix panic/deadlock sinking parquet with rows larger than 64MB estimated size (#25836)
- Fix quantile `midpoint` interpolation (#25824)
- Don't use cast when converting from physical in list.get (#25831)
- Invalid null count on int -> categorical cast (#25816)
- Update groups in `list.eval` (

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.37.0]_

### 1.36.1 — Python Polars 1.36.1

- Date: 2025-12-10
- Version: 1.36.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.36.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.36.1

- **changed** — Tune partitioned sink_parquet cloud performance
- **added** — Allow creation of Object literal
- **changed** — Don't collect schema in SQL union processing
- **fixed** — Don't invalidate node in cluster-with-columns
- **fixed** — Add missing type stubs for bin_slice, bin_head, and bin_tail
- **fixed** — Binary slice methods missing from Series and docs
- **fixed** — Mix-up of variable_name/value_name in unpivot
- **fixed** — Invalid usage of drop_first in to_dummies when nulls present
- **changed** — Upgrade to latest version of sqlparser-rs
- **fixed** — Update slab to version without RUSTSEC

##### 🚀 Performance improvements

- Tune partitioned sink\_parquet cloud performance (#25687)

##### ✨ Enhancements

- Allow creation of `Object` literal (#25690)
- Don't collect schema in SQL union processing (#25675)

##### 🐞 Bug fixes

- Don't invalidate node in cluster-with-columns (#25714)
- Move `boto3` extra from s3fs in dev requirements (#25667)
- Add missing type stubs for `bin_slice`, `bin_head`, and `bin_tail` (#25697)
- Binary slice methods missing from Series and docs (#25683)
- Mix-up of variable\_name/value\_name in unpivot (#25685)
- Invalid usage of `drop_first` in `to_dummies` when nulls present (#25435)

##### 📖 Documentation

- Fix typos in Excel and Pandas migration guides (#25709)
- Add "right" to `how` options in `join()` docstrings (#25678)

##### 🛠️ Other improvements

- Move Object `lit` fix earlier in the function (#25713)
- Remove unused decimal file (#25701)
- Move `boto3` extra from s3fs in dev requirements (#25667)
- Upgrade to latest version of `sqlparser-rs` (#25673)
- Update slab to version without RUSTSEC (#25686)
- Fix typo (#25684)

Thank you to all our contributors for making this release possible!
@AndreaBozzo, @Kevin-Patyk, @alexander-beedie, @dsprenkels, @jamesfricker, @mcrumiller, @nameexhaustion, @orlp and @ritchie46

### 1.36.0 — Python Polars 1.36.0

- Date: 2025-12-08
- Version: 1.36.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.36.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.36.0

- **added** — Add Extension types
- **added** — Add SQL support for the QUALIFY clause
- **added** — Add bin.slice(), bin.head(), and bin.tail() methods
- **added** — Add SQL syntax support for CROSS JOIN UNNEST(col)
- **added** — Add separate env var to log tracked metrics
- **added** — Expose fields for generating physical plan visualization data
- **added** — Add quantile for missing temporals
- **added** — Add strict parameter to pl.concat(how='horizontal')
- **added** — Support decimals in search_sorted
- **added** — Expose and document pl.Categories
- **added** — Extend SQL UNNEST support to handle multiple array expressions
- **added** — Add SQL support for ROW_NUMBER, RANK, and DENSE_RANK functions
- **added** — Add SQL support for named WINDOW references
- **added** — Add leftmost option to str.replace_many / str.find_many / str.extract_many
- **added** — Add maintain_order to Expr.mode
- **added** — Add empty_as_null and keep_nulls to {Lazy,Data}Frame.explode
- **added** — Add empty_as_null and keep_nulls flags to Expr.explode
- **added** — Support additional forms of SQL CREATE TABLE statements
- **added** — Add support for Float16 dtype
- **added** — Add unstable Schema.to_arrow()
- **changed** — Allow pl.Object in pivot value
- **changed** — Temporal quantile in rolling context
- **changed** — Allow elementwise Expr.over in aggregation context
- **changed** — Automatically Parquet dictionary encode floats
- **changed** — Support unique_counts for all datatypes
- **changed** — Allow hash for all List dtypes
- **changed** — Allow slice on scalar in aggregation context
- **changed** — Allow implode and aggregation in aggregation context
- **changed** — Move GraphMetrics into StreamingQuery
- **changed** — Allow Expr.unique on List/Array with non-numeric types
- **changed** — Allow Expr.rolling in aggregation contexts
- **changed** — Allow bare .row() on a single-row DataFrame, equivalent to .item() on a single-element DataFrame
- **changed** — Support column-positional SQL UNION operations
- **changed** — Make DSL-hash skippable
- **changed** — Support arbitrary expressions in SQL JOIN constraints
- **changed** — Allow arbitrary expressions as the Expr.rolling index_column
- **changed** — Support ewm_var/std in streaming engine
- **changed** — Add ignore_nulls to first / last
- **changed** — Allow arbitrary Expressions in subset parameter of unique frame method
- **changed** — Streaming {Expr,LazyFrame}.rolling
- **added** — Add LazyFrame.pivot
- **added** — Add SQL support for LEAD and LAG functions
- **added** — Add having to group_by context
- **added** — Add show methods for DataFrame and LazyFrame
- **fixed** — Fix streaming SchemaMismatch panic on list.drop_nulls
- **fixed** — Fix panic on Boolean rolling_sum calculation for list or array eval
- **fixed** — Fix panic edge-case when scanning hive partitioned data
- **fixed** — Fix empty format handling
- **fixed** — Improve SQL GROUP BY and ORDER BY expression resolution, handling aliasing edge-cases
- **fixed** — Preserve List inner dtype during chunked take operations
- **fixed** — Fix spearman panicking on nulls
- **fixed** — Properly resolve HAVING clause during SQL GROUP BY operations
- **fixed** — Prevent false positives in is_in for large integers
- **fixed** — Differentiate between empty list and no list for unpivot
- **fixed** — Bug in boolean unique_counts
- **fixed** — Hang in multi-chunk DataFrame .rows()

🏆 Highlights
- Add Extension types (#25322)

##### ✨ Enhancements

- Add SQL support for the QUALIFY clause (#25652)
- Add bin.slice(), bin.head(), and bin.tail() methods (#25647)
- Add SQL syntax support for CROSS JOIN UNNEST(col) (#25623)
- Add separate env var to log tracked metrics (#25586)
- Expose fields for generating physical plan visualization data (#25562)
- Allow pl.Object in pivot value (#25533)
- Minor improvement for as_struct repr (#25529)
- Temporal quantile in rolling context (#25479)
- Add quantile for missing temporals (#25464)
- Add strict parameter to pl.concat(how='horizontal') (#25452)
- Support decimals in search_sorted (#25450)
- Expose and document pl.Categories (#25443)
- Use reference to Graph pipes when flushing metrics (#25442)
- Extend SQL UNNEST support to handle multiple array expressions (#25418)
- Add SQL support for ROW_NUMBER, RANK, and DENSE_RANK functions (#25409)
- Allow elementwise Expr.over in aggregation context (#25402)
- Add SQL support for named WINDOW references (#25400)
- Add leftmost option to str.replace_many / str.find_many / str.extract_many (#25398)
- Automatically Parquet dictionary encode floats (#25387)
- Support unique_counts for all datatypes (#25379)
- Add maintain_order to Expr.mode (#25377)
- Allow hash for all List dtypes (#25372)
- Add empty_as_null and keep_nulls to {Lazy,Data}Frame.explode (#25369)
- Display function of streaming physical plan map node (#25368)
- Allow slice on scalar in aggregation context (#25358)
- Allow implode and aggregation in aggregation context (#25357)
- Move GraphMetrics into StreamingQuery (#25310)
- Documentation on Polars Cloud manifests (#25295)
- Add empty_as_null and keep_nulls flags to Expr.explode (#25289)
- Allow Expr.unique on List/Array with non-numeric types (#25285)
- Raise suitable error on non-integer "n" value for clear (#25266)
- Allow Expr.rolling in aggregation contexts (#25258)
- Allow bare .row() on a single-row DataFrame, equivalent to .item() on a single-element DataFrame (#25229)
- Support additional forms of SQL CREATE TABLE statements (#25191)
- Add support for Float16 dtype (#25185)
- Support column-positional SQL "UNION" operations (#25183)
- Add unstable `Schema.to_arrow()` (#25149)
- Make DSL-hash skippable (#25140)
- Improve error message on unsupported SQL subquery comparisons (#25135)
- Support arbitrary expressions in SQL `JOIN` constraints (#25132)
- Allow arbitrary expressions as the `Expr.rolling` `index_column` (#25117)
- Set polars/<version> user-agent (#25112)
- Support `ewm_var/std` in streaming engine (#25109)
- Rewrite `IR::Scan` to `IR::DataFrameScan` in `expand_datasets` when applicable (#25106)
- Add ignore_nulls to first / last (#25105)
- Allow arbitrary Expressions in "subset" parameter of `unique` frame method (#25099)
- Add `BIT_NOT` support to the SQL interface (#25094)
- Streaming `{Expr,LazyFrame}.rolling` (#25058)
- Add LazyFrame.pivot (#25016)
- Add SQL support for `LEAD` and `LAG` functions (#23956)
- Add having to group_by context (#23550)
- Add show methods for DataFrame and LazyFrame (#19634)

##### 🚀 Performance improvements

- Set parallelization threshold in `take_unchecked_impl` (#25672)
- New single file IO sink pipeline enabled for sink_parquet (#25670)
- Correct overly eager local predicate insertion for unpivot (#25644)
- New partitioned IO sink pipeline enabled for sink_parquet (#25629)
- Use strong hash instead of traversal for CSPE equality (#25537)
- Reduce HuggingFace API calls (#25521)
- Fix panic in is_between support in streaming Parquet predicate push down (#25476)
- Faster kernels for rle_lengths (#25448)
- Mark output of more non-order-maintaining ops as unordered (#25419)
- Enable predicate expressions on unsigned integers (#25416)
- Allow detecting plan sortedness in more cases (#25408)
- Add parquet prefiltering for string regexes (#25381)
- Fast find start window in group_by_dynamic

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.36.0]_

### 1.36.0-beta.2 — Python Polars 1.36.0-beta.2

- Date: 2025-12-02
- Version: 1.36.0-beta.2
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.36.0-beta.2
- Permalink: https://whatsnew.fyi/product/polars/releases/1.36.0-beta.2
- Labels: Pre-release

- **added** — Add Extension types
- **added** — Add SQL support for ROW_NUMBER, RANK, and DENSE_RANK functions
- **added** — Add SQL support for named WINDOW references
- **added** — Add BIT_NOT support to the SQL interface
- **added** — Add LazyFrame.pivot
- **added** — Add allow_empty flag to item
- **added** — Add empty_as_null and keep_nulls flags to Expr.explode
- **added** — Add empty_as_null and keep_nulls to {Lazy,Data}Frame.explode
- **added** — Add having to group_by context
- **added** — Add ignore_nulls to first / last
- **added** — Add maintain_order to Expr.mode
- **added** — Add quantile for missing temporals
- **added** — Add leftmost option to str.replace_many / str.find_many / str.extract_many
- **added** — Add strict parameter to pl.concat(how='horizontal')
- **added** — Add support for Float16 dtype
- **added** — Add unstable Schema.to_arrow
- **changed** — Allow Expr.rolling in aggregation contexts
- **changed** — Allow Expr.unique on List/Array with non-numeric types
- **changed** — Allow glimpse to return a DataFrame
- **changed** — Allow hash for all List dtypes

##### 🏆 Highlights

- Add Extension types (#25322)

##### ✨ Enhancements

- Add SQL support for `ROW_NUMBER`, `RANK`, and `DENSE_RANK` functions (#25409)
- Add SQL support for named `WINDOW` references (#25400)
- Add `BIT_NOT` support to the SQL interface (#25094)
- Add `LazyFrame.pivot` (#25016)
- Add `allow_empty` flag to `item` (#25048)
- Add `empty_as_null` and `keep_nulls` flags to `Expr.explode` (#25289)
- Add `empty_as_null` and `keep_nulls` to `{Lazy,Data}Frame.explode` (#25369)
- Add `having` to `group_by` context (#23550)
- Add `ignore_nulls` to `first` / `last` (#25105)
- Add `maintain_order` to `Expr.mode` (#25377)
- Add `quantile` for missing temporals (#25464)
- Add leftmost option to `str.replace_many / str.find_many / str.extract_many` (#25398)
- Add strict parameter to pl.concat(how='horizontal') (#25452)
- Add support for `Float16` dtype (#25185)
- Add unstable `Schema.to_arrow` (#25149)
- Allow `Expr.rolling` in aggregation contexts (#25258)
- Allow `Expr.unique` on `List`/`Array` with non-numeric types (#25285)
- Allow `glimpse` to return a `DataFrame` (#24803)
- Allow `hash` for all `List` dtypes (#25372)
- Allow `implode` and aggregation in aggregation context (#25357)
- Allow `slice` on scalar in aggregation context (#25358)
- Allow arbitrary Expressions in "subset" parameter of `unique` frame method (#25099)
- Allow arbitrary expressions as the `Expr.rolling` `index_column` (#25117)
- Allow bare `.row` on a single-row DataFrame, equivalent to `.item` on a single-element DataFrame (#25229)
- Allow elementwise `Expr.over` in aggregation context (#25402)
- Allow pl.Object in pivot value (#25533)
- Automatically Parquet dictionary encode floats (#25387)
- Display function of streaming physical plan `map` node (#25368)
- Documentation on Polars Cloud manifests (#25295)
- Expose and document pl.Categories (#25443)
- Expose fields for generating physical plan visualization data (#25562)
- Extend SQL `UNNEST` support to handle multiple array expressions (#25418)
- Improve SQL `UNNEST` behaviour (#22546)
- Improve error message on unsupported SQL subquery comparisons (#25135)
- Make DSL-hash skippable (#25140)
- Minor improvement for `as_struct` repr (#25529)
- Move GraphMetrics into StreamingQuery (#25310)
- Raise suitable error on non-integer "n" value for `clear` (#25266)
- Rewrite `IR::Scan` to `IR::DataFrameScan` in `expand_datasets` when applicable (#25106)
- Set polars/<version> user-agent (#25112)
- Streaming `{Expr,LazyFrame}.rolling` (#25058)
- Support BYTE_ARRAY backed Decimals in Parquet (#25076)
- Support `ewm_var/std` in streaming engine (#25109)
- Support `unique_counts` for all datatypes (#25379)
- Support additional forms of SQL "CREATE TABLE" statements (#25191)
- Support arbitrary expressions in SQL `JOIN` constraints (#25132)
- Support column-positional SQL "UNION" operations (#25183)
- Support decimals in search_sorted (#25450)
- Temporal `quantile` in rolling context (#25479)
- Use reference to Graph pipes when flushing metrics (#25442)

##### 🚀 Performance improvements

- Add parquet prefiltering for string regexes (#25381)
- Add streaming native `LazyFrame.group_by_dynamic` (#25342)
- Add streaming sorted Group-By (#25013)
- Allow detecting plan sortedness in more cases (#25408)
- Don't recompute full rolling moment window when NaNs/nulls leave the window (#25078)
- Enable predicate expressions on unsigned integers (#25416)
- Fast find start window in `group_by_dynamic` with large `offset` (#25376)
- Faster kernels for rle_lengths (#25448)
- Fuse positive `slice` into streaming `LazyFrame.rolling` (#25338)
- Lazy gather for `{forward,backward}_fill` in group-by contexts (#25115)
- Mark `Expr.reshape((-1,))` as row separable (#25326)
- Mark output of more non-order-maintaining ops as unordered (#25419)
- Optimize ipc stream read performance (#24671)
- Reduce HuggingFace API calls (#25521)
- Return references from `a

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.36.0-beta.2]_

### 1.35.2 — Python Polars 1.35.2

- Date: 2025-11-09
- Version: 1.35.2
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.35.2
- Permalink: https://whatsnew.fyi/product/polars/releases/1.35.2

- **fixed** — Fix incorrect drop_nans() result when used in group_by() / over()
- **fixed** — Fix handling Null dtype in ApplyExpr on group_by
- **fixed** — Fix assertion panic on group_by
- **fixed** — Fix wide-table join performance regression

* Fix incorrect `drop_nans()` result when used in `group_by()` / `over()` (https://github.com/pola-rs/polars/pull/25146)
* Fix handling `Null` dtype in `ApplyExpr` on `group_by`(https://github.com/pola-rs/polars/pull/25077)
* Fix assertion panic on `group_by` (https://github.com/pola-rs/polars/pull/25179)
* Fix Wide-table join performance regression (https://github.com/pola-rs/polars/pull/25222)

Thank you to all our contributors for making this release possible!
@coastalwhite, @kdn36, @nameexhaustion and @ritchie46

### 1.35.1 — Python Polars 1.35.1

- Date: 2025-10-30
- Version: 1.35.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.35.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.35.1

- **changed** — Don't recompute full rolling moment window when NaNs/nulls leave the window
- **changed** — Skip filtering scan IR if no paths were filtered
- **changed** — Optimize ipc stream read performance
- **added** — Support BYTE_ARRAY backed Decimals in Parquet
- **changed** — Allow glimpse to return a DataFrame
- **added** — Add allow_empty flag to item
- **fixed** — The SQL interface should use logical, not bitwise, behaviour for unary NOT operator
- **fixed** — Fix panic if scan predicate produces 0 length mask
- **fixed** — Ensure SQL table alias resolution checks against CTE aliases on fallback
- **fixed** — Fix panic in group_by_dynamic with group_by and multiple chunks
- **fixed** — Fix panic when using struct field as join key
- **fixed** — Allow broadcast in group_by for ApplyExpr and BinaryExpr
- **fixed** — Fix field metadata for nested categorical PyCapsule export
- **fixed** — Block predicate pushdown when group_by key values are changed
- **fixed** — Fix group-by aggregation problems caused by AmortSeries
- **fixed** — Don't push down predicates passed inserted cache nodes
- **fixed** — Allow for negative time in group_by_dynamic iterator
- **changed** — Change group length mismatch error to ShapeError

##### 🚀 Performance improvements

- Don't recompute full rolling moment window when NaNs/nulls leave the window (#25078)
- Skip filtering scan IR if no paths were filtered (#25037)
- Optimize ipc stream read performance (#24671)

##### ✨ Enhancements

- Support BYTE\_ARRAY backed Decimals in Parquet (#25076)
- Allow `glimpse` to return a `DataFrame` (#24803)
- Add `allow_empty` flag to `item` (#25048)

##### 🐞 Bug fixes

- The `SQL` interface should use logical, not bitwise, behaviour for unary "NOT" operator (#25091)
- Fix panic if scan predicate produces 0 length mask (#25089)
- Ensure SQL table alias resolution checks against CTE aliases on fallback (#25071)
- Panic in `group_by_dynamic` with `group_by` and multiple chunks (#25075)
- Minor improvement to internal `is_pycapsule` utility function (#25073)
- Fix panic when using struct field as join key (#25059)
- Allow broadcast in `group_by` for `ApplyExpr` and `BinaryExpr` (#25053)
- Fix field metadata for nested categorical PyCapsule export (#25052)
- Block predicate pushdown when `group_by` key values are changed (#25032)
- Group-By aggregation problems caused by `AmortSeries` (#25043)
- Don't push down predicates passed inserted cache nodes (#25042)
- Allow for negative time in `group_by_dynamic` iterator (#25041)

##### 📖 Documentation

- Fix typo in public dataset URL (#25044)

##### 🛠️ Other improvements

- Disable recursive CSPE for now (#25085)
- Change group length mismatch error to `ShapeError` (#25004)
- Update toolchain (#25007)

Thank you to all our contributors for making this release possible!
@Kevin-Patyk, @Liyixin95, @alexander-beedie, @coastalwhite, @kdn36, @nameexhaustion, @orlp, @r-brink, @ritchie46 and @stijnherfst

### 1.35.0 — Python Polars 1.35.0

- Date: 2025-10-26
- Version: 1.35.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.35.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.35.0

- **added** — Add Expr.item to strictly extract a single value from an expression
- **added** — Add list.agg and arr.agg
- **added** — Implement {Expr,Series}.rolling_rank()
- **added** — Add arr.eval
- **added** — Add union() function for unordered concatenation
- **added** — Add name.replace to the set of column rename options
- **added** — Add separator to {Data,Lazy}Frame.unnest
- **added** — Add glob parameter to scan_ipc
- **added** — Add environment variable to roundtrip empty struct in Parquet
- **added** — Add streaming engine per-node metrics
- **added** — Add support for UInt128 to pyo3-polars
- **changed** — Stabilize decimal
- **changed** — Support ewm_mean() in streaming engine
- **changed** — Allow local scans on polars cloud (configurable)
- **changed** — Support MergeSorted in CSPE
- **changed** — Make Series init consistent with DataFrame init for string values declared with temporal dtype
- **changed** — Improve rolling_(sum|mean) accuracy
- **changed** — Allow duration strings with leading "+"
- **changed** — Support np.ndarray -> AnyValue conversion
- **fixed** — Fix incorrect join_asof on a casted expression

##### 🏆 Highlights

- Stabilize decimal (#25020)

##### 🚀 Performance improvements

- Bump foldhash to 0.2.0 and hashbrown to 0.16.0 (#25014)
- Lower `unique` to native group-by and speed up `n_unique` in group-by context (#24976)
- Better parallelize `take{_slice,}_unchecked` (#24980)
- Implement native `skew` and `kurtosis` in group-by context (#24961)
- Use native group-by aggregations for `bitwise_*` operations (#24935)
- Address `group_by_dynamic` slowness in sparse data (#24916)
- Push filters to PyIceberg (#24910)
- Native `filter/drop_nulls/drop_nans` in group-by context (#24897)
- Implement `cumulative_eval` using the group-by engine (#24889)
- Prevent generation of copies of `Dataframe`s in `DslPlan` serialization (#24852)
- Implement native `null_count`, `any` and `all` group-by aggregations (#24859)
- Speed up `reverse` in group-by context (#24855)
- Prune unused categorical values when exporting to arrow/parquet/IPC/pickle (#24829)
- Don't check duplicates on streaming simple projection in release mode (#24830)
- Lower approx\_n\_unique to the streaming engine (#24821)
- Duration/interval string parsing optimisation (2-5x faster) (#24771)
- Use native reducer for `first/last` on Decimals, Categoricals and Enums (#24786)
- Implement indexed method for `BitMapIter::nth` (#24766)
- Pushdown slices on plans within unions (#24735)

##### ✨ Enhancements

- Stabilize decimal (#25020)
- Support `ewm_mean()` in streaming engine (#25003)
- Improve row-count estimates (#24996)
- Remove filtered scan paths in IR when possible (#24974)
- Introduce remote Polars MCP server (#24977)
- Allow local scans on polars cloud (configurable) (#24962)
- Add `Expr.item` to strictly extract a single value from an expression (#24888)
- Add environment variable to roundtrip empty struct in Parquet (#24914)
- Fast-count for `scan_iceberg().select(len())` (#24602)
- Add `glob` parameter to `scan_ipc` (#24898)
- Prevent generation of copies of `Dataframe`s in `DslPlan` serialization (#24852)
- Add `list.agg` and `arr.agg` (#24790)
- Implement `{Expr,Series}.rolling_rank()` (#24776)
- Don't require PyArrow for `read_database_uri` if ADBC engine version supports PyCapsule interface (#24029)
- Make `Series` init consistent with `DataFrame` init for string values declared with temporal dtype (#24785)
- Support MergeSorted in CSPE (#24805)
- Duration/interval string parsing optimisation (2-5x faster) (#24771)
- Recursively apply CSPE (#24798)
- Add streaming engine per-node metrics (#24788)
- Add `arr.eval` (#24472)
- Drop PyArrow requirement for non-batched usage of `read_database` with the ADBC engine and support `iter_batches` with the ADBC engine (#24180)
- Improve rolling\_(sum|mean) accuracy (#24743)
- Add `separator` to `{Data,Lazy}Frame.unnest` (#24716)
- Add `union()` function for unordered concatenation (#24298)
- Add `name.replace` to the set of column rename options (#17942)
- Support `np.ndarray -> AnyValue` conversion (#24748)
- Allow duration strings with leading "+" (#24737)
- Drop now-unnecessary post-init "schema\_overrides" cast on `DataFrame` load from list of dicts (#24739)
- Add support for UInt128 to pyo3-polars (#24731)

##### 🐞 Bug fixes

- Re-enable CPU feature check before import (#25010)
- Implement `read_excel` workaround for fastexcel/calamine issue loading a column subset from a named table (#25012)
- Correctness `any(ignore_nulls)` and OOB in `all` (#25005)
- Streaming any/all with ignore\_nulls=False (#25008)
- Fix incorrect `join_asof` on a casted expression (#25006)
- Optimize memory on rolling groups in `ApplyExpr` (#24709)
- Fallback `Pyarrow` scan to in-memory engine (#24991)
- Make `Operator::swap_operands` return correct operators for `Plus`, `Minus`, `Multiply` and `Divide` (#24997)
- Capitalize letters after numbers in to\_titlecase (#24993)
- Preserve null values in `pct_change` (#24952)
- Raise length mismatch on `over` with sliced groups (#24887)
- Check duplicate name in transpose (#24956)
- Follow Kle

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.35.0]_

### 1.35.0-beta.1 — Python Polars 1.35.0-beta.1

- Date: 2025-10-19
- Version: 1.35.0-beta.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.35.0-beta.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.35.0-beta.1
- Labels: Pre-release

- **changed** — Address group_by_dynamic slowness in sparse data
- **changed** — Push filters to PyIceberg
- **changed** — Implement native filter/drop_nulls/drop_nans in group-by context
- **changed** — Implement cumulative_eval using the group-by engine
- **changed** — Prevent generation of copies of Dataframes in DslPlan serialization
- **changed** — Implement native null_count, any and all group-by aggregations
- **changed** — Speed up reverse in group-by context
- **changed** — Prune unused categorical values when exporting to arrow/parquet/IPC/pickle
- **changed** — Lower approx_n_unique to the streaming engine
- **changed** — Duration/interval string parsing is 2-5x faster
- **changed** — Use native reducer for first/last on Decimals, Categoricals and Enums
- **added** — Add environment variable to roundtrip empty struct in Parquet
- **added** — Add glob parameter to scan_ipc
- **added** — Add list.agg and arr.agg
- **added** — Implement {Expr,Series}.rolling_rank()
- **added** — Add arr.eval
- **added** — Add separator to {Data,Lazy}Frame.unnest
- **added** — Add union() function for unordered concatenation
- **added** — Add name.replace to the set of column rename options
- **fixed** — Fix repeated with_row_index() after scan() silently ignored

##### 🚀 Performance improvements

- Address `group_by_dynamic` slowness in sparse data (#24916)
- Push filters to PyIceberg (#24910)
- Native `filter/drop_nulls/drop_nans` in group-by context (#24897)
- Implement `cumulative_eval` using the group-by engine (#24889)
- Prevent generation of copies of `Dataframe`s in `DslPlan` serialization (#24852)
- Implement native `null_count`, `any` and `all` group-by aggregations (#24859)
- Speed up `reverse` in group-by context (#24855)
- Prune unused categorical values when exporting to arrow/parquet/IPC/pickle (#24829)
- Don't check duplicates on streaming simple projection in release mode (#24830)
- Lower approx\_n\_unique to the streaming engine (#24821)
- Duration/interval string parsing optimisation (2-5x faster) (#24771)
- Use native reducer for `first/last` on Decimals, Categoricals and Enums (#24786)
- Implement indexed method for `BitMapIter::nth` (#24766)
- Pushdown slices on plans within unions (#24735)

##### ✨ Enhancements

- Add environment variable to roundtrip empty struct in Parquet (#24914)
- Fast-count for `scan_iceberg().select(len())` (#24602)
- Add `glob` parameter to `scan_ipc` (#24898)
- Prevent generation of copies of `Dataframe`s in `DslPlan` serialization (#24852)
- Add `list.agg` and `arr.agg` (#24790)
- Implement `{Expr,Series}.rolling_rank()` (#24776)
- Don't require PyArrow for `read_database_uri` if ADBC engine version supports PyCapsule interface (#24029)
- Make `Series` init consistent with `DataFrame` init for string values declared with temporal dtype (#24785)
- Support MergeSorted in CSPE (#24805)
- Duration/interval string parsing optimisation (2-5x faster) (#24771)
- Recursively apply CSPE (#24798)
- Add streaming engine per-node metrics (#24788)
- Add `arr.eval` (#24472)
- Drop PyArrow requirement for non-batched usage of `read_database` with the ADBC engine and support `iter_batches` with the ADBC engine (#24180)
- Improve rolling\_(sum|mean) accuracy (#24743)
- Add `separator` to `{Data,Lazy}Frame.unnest` (#24716)
- Add `union()` function for unordered concatenation (#24298)
- Add `name.replace` to the set of column rename options (#17942)
- Support `np.ndarray -> AnyValue` conversion (#24748)
- Allow duration strings with leading "+" (#24737)
- Drop now-unnecessary post-init "schema\_overrides" cast on `DataFrame` load from list of dicts (#24739)
- Add support for UInt128 to pyo3-polars (#24731)

##### 🐞 Bug fixes

- Properly release the GIL for `read_parquet_metadata` (#24922)
- Broadcast `partition_by` columns in `over` expression (#24874)
- Clear index cache on stacked `df.filter` expressions (#24870)
- Fix 'explode' mapping strategy on scalar value (#24861)
- Fix repeated `with_row_index()` after `scan()` silently ignored (#24866)
- Correctly return min and max for enums in groupby aggregation (#24808)
- Refactor `BinaryExpr` in `group_by` dispatch logic (#24548)
- Fix aggstate for `gather` (#24857)
- Keep scalars for length preserving functions in `group_by` (#24819)
- Have `range` feature depend on `dtype-array` feature (#24853)
- Fix duplicate select panic (#24836)
- Inconsistency of list.sum() result type with None values (#24476)
- Division by zero in Expr.dt.truncate (#24832)
- Potential deadlock in \_\_arrow\_c\_stream\_\_ (#24831)
- Allow double aggregations in group-by contexts (#24823)
- Series.shrink\_dtype for i128/u128 (#24833)
- Fix dtype in `EvalExpr` (#24650)
- Allow aggregations on `AggState::LiteralScalar` (#24820)
- Dispatch to `group_aware` for fallible expressions with masked out elements (#24815)
- Fix error for `arr.sum()` on small integer Array dtypes containing nulls (#24478)
- Fix regression on `write_database()` to Snowflake due to unsupported string view type (#24622)
- Fix XOR did not follow kleene when one side is unit-length (#24810)
- Make `Series` init consistent with `DataFrame` init for string values declared with temporal dtype (#24785)
- Incorrect precision in Series.str.to\_decimal (#24804)
- Use `overl

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.35.0-beta.1]_