py-1.40.0

## 🏆 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\_graph (#27144)
- Skip extension types for min/max in describe (#27120)
- Address a potential overflow in `from_epoch` scaling (#27118)
- Fix incorrect IO metrics on multi-phase streaming execution (#27123)
- Use delta stats for mixed hive and non-hive predicate pushdown (#27102)
- Make the files used in docs available locally (#27121)
- Apply scalar bound in `clip` when the Series bound contains nulls (#27087)
- Ignore `ddof` parameter in `rolling_corr` and deprecate (#27104)
- Preserve casts for horizontal ops with untyped literals (#27011)
- Reject invalid input to `sql_expr` (#27084)
- Ensure SQL `COUNT(<lit>)` expressions return the correct value (#27085)
- Regression in replace\_strict for enums (#27066)
- Make `test_group_by_arg_max_boolean_26978` non-flaky for `max_by` ties (#27048)
- Null count for aggregated list inside count aggregation (#27032)
- Panic in streaming MergeSortedNode (#27024)
- Prevent panic in `transpose()` with mixed List and non-List columns (#27038)
- Set sorted flag for Boolean and Time (#27035)
- Missing `src/` subdirectory to CI Python docs step (#27025)
- Resolve stack overflow on `merge_sorted` and `union` (#27018)
- Make `pl.DataFrame.fill_null` work on columns with `Null` dtype (#27020)
- Fix repeated word typos in comments (#26917)
- Covariance with constant is zero, not NaN (#27015)
- Don't remove `set_sorted` in projection pushdown (#27006)
- Infer nulls when df create from empty-struct (#26991)
- Correct suggestion in multi-expr filter error (#27003)
- Implement `agg_arg_min`/`agg_arg_max` for `boolean` data type (#26997)
- Ensure `sample()`  respects the global set seed (#26992)

## 📖 Documentation

- Add documentation for openlineage on-premises (#27334)
- Release page (#27335)
- Update uv pip install polars-on-premises cmd (#27330)
- Fix outdated `LazyGroupBy.map_groups` docstring (#27292)
- Add `deny_anonymous_users` to scheduler config (#27287)
- Slurm documentation (#27259)
- Add link to concepts in index.md (#27077)
- Add docs entry for `merge_sorted` (#27224)
- Fix typo (#27212)
- Make the files used in docs available locally (#27121)
- Put first-time contribution requirements in its own linkable section (#27113)
- Add missing docstrings for Expr.struct.\_\_getitem\_\_ and Series.\_\_setitem\_\_ (#27092)
- Normalise `Series` docstring whitespace indents (#27082)
- Change Polars Cloud API to 0.6.0 (#27005)
- Improve `write_parquet` docstring for `use_pyarrow` (#26988)

## 📦 Build system

- Really do not install pyiceberg-core 0.9.0 (#27017)

## 🛠️ Other improvements

- Add regression test for instantiating polars DataFrame from pandas Timestamp (#27332)
- Bump Python Polars version (#27315)
- Resolve bad instantiations in test\_iceberg (#27314)
- Sink DSL and callback for Iceberg (#27258)
- Wait for morsel consumption in merge\_sorted streaming node (#27288)
- Use more precise internal typing (pt. iii) (#27232)
- Mark `scan_ipc` cache arguments as deprecated (#27216)
- Consolidate reordered compare functions (#27229)
- Fix `test_dtype_concat_3735` not actually iterating through numeric dtypes (#27178)
- Remove dead code in `test_scan_lines` (#27213)
- Move/genericize `_balanced_reduce` to Python utils (#27100)
- Remove unused attributes (#27191)
- Avoid unnecessary recompilation due to changing env vars (#27166)
- Update nightly Rust compiler version (#27145)
- Simplify pyarrow scan and process in batches (#26982)
- Make internal typing more precise (part ii) (#27117)
- Add None \& Dataframe to FrameInitTypes (#27126)
- Remove unused expression sorts (#27075)
- Improve internal typing ahead of using `ty` / `pyrefly` (#27050)
- Add explicit `ResourceWarning` coverage (#27083)
- Add sinked paths callback (#26995)
- Pin maturin due to compile time regression (#27062)
- Missing `src/` subdirectory to CI Python docs step (#27025)
- Really do not install pyiceberg-core 0.9.0 (#27017)
- Naming for named scopes (#26999)
- Enable hypothesis tests when `POLARS_AUTO_NEW_STREAMING=1` (#26818)
- Fix CI by excluding missing wheel version of pyiceberg (#27001)
- Remove indirection in calling python scans (#26981)
- Polars versions (#26980)

Thank you to all our contributors for making this release possible!
@0xRozier, @EndPositive, @HCYT, @Kevin-Patyk, @MarcoGorelli, @NeejWeej, @RedZapdos123, @TNieuwdorp, @abhidotsh, @alexander-beedie, @andyjessen, @azimafroozeh, @borchero, @carnarez, @coastalwhite, @debnathshoham, @dpinol, @dsprenkels, @dydev012, @farouk-01, @gab23r, @gautamvarmadatla, @joaquinhuigomez, @kdn36, @nameexhaustion, @orlp, @ritchie46, @wence-, @xenzh, @yangsong97 and @yonatan-genai