split out rolling_*(..., by='foo') into rolling_*_by('foo', ...) (#16059)
add date pattern dd.mm.YYYY (#16045)
split Expr.top_k and Expr.top_k_by into separate functions (#16041)
Support non-coalescing joins in default engine (#16036)
Support pytorch Tensor and Dataset export with new to_torch DataFrame/Series method (#15931)
Minor DB type inference updates (#16030)
Move diagonal & horizontal concat schema resolving to IR phase (#16034)
raise more informative error messages in rolling_* aggregations instead of panicking (#15979)
Convert concat during IR conversion (#16016)
Improve dynamic supertypes (#16009)
Additional uint datatype support for the SQL interface (#15993)
Add post-optimization callback (#15972)
Support Decimal read from IPC (#15965)
Expose plan and expression nodes through NodeTraverser to Python (#15776)
Add typed collection from par iterators (#15961)
Add by argument for Expr.top_k and Expr.bottom_k (#15468)

🐞 Bug fixes

Respect user passed 'reader_schema' in 'scan_csv' (#16080)
Lazy csv + projection; respect null values arg (#16077)
Materialize dtypes when converting to arrow (#16074)
Fix casting decimal to decimal for high precision (#16049)
Fix Series constructor failure for Array types for large integers (#16050)
Fix printing max scale decimals (#16048)
Decimal supertype for dyn int (#16046)
Correctly handle large timedelta objects in Series constructor (#16043)
Do not close connection just because we're not returning Arrow data in batches (#16031)
properly handle nulls in DictionaryArray::iter_typed (#16013)
Fix CSE case where upper plan has no projection (#16011)
Crash/incorrect group_by/n_unique on categoricals created by (q)cut (#16006)
converting from numpy datetime64 and overriding dtype with a different resolution was returning incorrect results (#15994)
Ternary supertype dynamics (#15995)
Fix PartialEq for DataType::Unknown (#15992)
Finish adding typed_lit to help schema determination in SQL "extract" func (#15955)
Fix dtype parameter in pandas_to_pyseries function (#15948)
do not panic when comparing against categorical with incompatible dtype (#15857)
Join validation for multiple keys (#15947)
Add missing "truncate_ragged_lines" parameter to read_csv_batched (#15944)

📖 Documentation

Ensure consistent docstring warning in fill_nan methods (pointing out that nan isn't null) (#16061)
add filter docstring examples to date and datetime (#15996)
Fix docstring mistake for polars.concat_str (#15937)
Update reference to apply (#15982)
Remove unwanted linebreaks from docstrings (#16002)
correct default in rolling_* function examples (#16000)
Improve user-guide doc of UDF (#15923)
update the link to R API docs (#15973)

🛠️ Other improvements

Bump sccache action (#16088)
Fix failures in test coverage workflow (#16083)
Update benchmarks/coverage jobs with "requirements-ci" (#16072)
Add TypeGuard to is_polars_dtype util (#16065)
Clean up hypothesis decimal strategy (#16056)
split Expr.top_k and Expr.top_k_by into separate functions (#16041)
Use UnionArgs for DSL side (#16017)
Add some comments (#16008)
Improve hypothesis strategy for decimals (#16001)
Set up TPC-H benchmark tests (#15908)
Even more Pyo3 0.21 Bound<> APIs (#15914)
Fix failing test (#15936)

Thank you to all our contributors for making this release possible! @CanglongCl, @JulianCologne, @KDruzhkin, @MarcoGorelli, @alexander-beedie, @avimallu, @bertiewooster, @c-peters, @dependabot, @dependabot[bot], @eitsupi, @haocheng6, @itamarst, @luke396, @marenwestermann, @nameexhaustion, @orlp, @ritchie46, @stinodego, @thalassemia, @wence- and @wsyxbcl