Add fast paths for series.arg_sort and dataframe.sort (#19872)
Utilize the RangedUniqueKernel for Enum/Categorical (#20150)
Reduce memory copy when scanning from Python objects (#20142)
Don't instantiate validity mask when unneeded in Parquet (#20149)
Expand more filters (#20022)
Cache the DataFrame schema in get_column_index (#20021)
Reduce the size of row encoding UTF-8 (#19911)
Memoize duplicates in rolling-gb-dyn (#19939)
More efficient row encoding for pl.List (#19907)
Half the size of Booleans in row encoding (#19927)
Rolling 'iter_lookbehind' breeze through duplicates (#19922)
Initially trim leading and trailing filtered rows (#19850)
Increase default async thread count for low core count systems (#19829)
Move row group decode off async thread for local streaming parquet scan (#19828)
Support use of Duration in to_string, ergonomic/perf improvement, tz-aware Datetime bugfix (#19697)
Improve DataFrame.sort().limit/top_k performance (#19731)
Improve cloud scan performance (#19728)
Fix quadratic 'with_columns' behavior (#19701)
Improve hive partition pruning with datetime predicates from SQL (#19680)
Allow for arbitrary skips in Parquet Dictionary Decoding (#19649)
Reorder conditions in is_leap_year (#19602)
Rechunk in DataFrame.rows if needed (#19628)
Dispatch Parquet Primitive PLAIN decoding to faster kernels when possible (#19611)
Use faster iteration in 'starts_with'/'ends_with' (#19583)
Branchless Parquet Prefiltering (#19190)

✨ Enhancements

Retry with reloaded credentials on cloud error (#20185)
Support reading Enum dtype from csv (#20188)
Allow sorting of lists and arrays (#20169)
Add maintain_order parameter to joins (#20026)
Allow for to_datetime / strftime to automatically parse dates with single-digit hour/minute/second (#20144)
Experimental cloud write support (#20129)
Allow setting and reading custom schema-level IPC metadata (#20066)
Add optimized row encoding for Decimals (#20050)
Add drop_nans method to DataFrame and LazyFrame (#20029)
Catch use of 'polars' in to_string for non-Duration dtypes and raise an informative error (#19977)
Add AhoCorasick backed 'find_many' (#19952)
Speed up starts_with for small prefixes (#19904)
Auto-enable hive partitioning if hive_schema was given (#19902)
Add pl.concat_arr to concatenate columns into an Array column (#19881)
Support both "iso" and "iso:strict" format options for dt.to_string (#19840)
Add rounding for Decimal type (#19760)
Improved array arithmetic support (#19837)
Raise informative error on Unknown unnest (#19830)
Support use of Duration in to_string, ergonomic/perf improvement, tz-aware Datetime bugfix (#19697)
Allow specification of chunk_size on LazyCsvReader.read_options (#19819)
Add an is_literal method to expression meta namespace (#19773)
A different approach to warning users of fork() issues with Polars (#19197)
Add dylib (#19759)
Add IPC source node for new streaming engine (#19454)
Implement max/min methods for dtypes (#19494)
Improve hive partition pruning with datetime predicates from SQL (#19680)
Parallel IPC sink for the new streaming engine (#19622)
Add SQL support for RIGHT JOIN, fix an issue with wildcard aliasing (#19626)
Add show_graph to display a GraphViz plot for expressions (#19365)

🐞 Bug fixes

Don't trigger length check in array construction (#20205)
Allow row encoding for 32-bit architectures (e.g. WASM) (#20186)
Properly project unordered column in parquet prefiltered (#20189)
Csv stop simd cache if eol char is hit (#20199)
Estimated size for object (#20191)
Respect parallel argument in parquet (#20187)
Only validate UTF-8 for selected items when all below len 128 (#20183)
Serialize categories of Enum in arrow metadata (#20181)
Don't use RLE encoding for Parquet Boolean (#20172)
Invalid bitwise_xor for ScalarColumn (#20140)
Add temporal feature gate in is_elementwise_top_level (#20177)
Column name mismatch or not found in Parquet scan with filter (#20178)
Raise if apply returns different types (#20168)
Deal with masked out list elements (#20161)
Fix index out of bounds in uniform_hist_count (#20133)
Implement arg_sort for Null series (#20135)
Handle slice pushdown in PythonUDF GroupBy (#20132)
Check shape for *_horizontal functions (#20130)
Properly coerce types in lists (#20126)
Incorrect aggregation of empty groups after slice (#20127)
DataFrame .get_column after drop_in_place (#20120)
Subtraction with underflow on empty FixedSizeBinaryArray (#20109)
Materialize smallest dyn ints to use feature gate for i8/i16 (#20108)
Return null instead of 0. for rolling_std when window contains a single element and ddof=1 and there are nulls elsewhere in the Series (#20077)
Only slice after sort when slice is smaller than frame length (#20084)
Preserve Series name in __rpow__ operation (#20072)
Allow nested is_in() in when()/then() for full-streaming (#20052)
Fix datetime cast behavior for pre-epoch times (#19949)
Improve hist binning around breakpoints (#20054)
Fix invalid len due to projection pushdown selection of scalar (#20049)
Fix empty scalar agg type (#20051)
Improve binning in Series.hist with bin_count when all values are the same (#20034)
Less intrusive forking warnings (#20032)
Reading nullable sliced / masked Categoricals from Parquet (#20024)
Regression in hist panicking on out of bounds index (#20016)
Fix starts_with out of bounds (#20006)
Fix incorrect column order for parquet scan with hive columns in file (#19996)
Incorrectly gave list.len() for masked-out rows (#19999)
Bug fix in existing fast path for sorted series (#20004)
Incorrect collect_schema() for fill_null() after an aggregation expression in group-by context (#19993)
Fix Decimal type fill_null (#19981)
Fix panic on schema merge for prefiltering (#19972)
Fix lazy frame join expression (#19974)
Fix gather_every for Scalar (#19964)
Toggle 'fast_unique' on new_from_index (#19956)
Raise proper error message when too small interval is passed to datetime_range (#19955)
Fix scalar object (#19940)
Raise InvalidOperationError for invalid float to decimal casts (e.g. Inf, NaN) (#19938)
Fix panic with combination of hive and parquet prefiltering (#19905)
Fix panic when joining with empty frame (debug only) (#19896)
Fix incorrect result from inequality filter after join on LazyFrame (#19898)
Misleading ShapeError error message on dataframe creation (#19901)
Fix panic with empty delta scan, or empty parquet scan with a provided schema (#19884)
Ensure type object of inputs for cached any-value conversion functions are kept alive (#19866)
Fix panic using scan_parquet().with_row_index() with hive partitioning enabled (#19865)
Improve histogram bin logic (#18761)
Raise informative error instead of panicking for list arithmetic on some invalid dtypes (#19841)
Properly handle Zero-Field Structs in row encoding (#19846)
Incorrect explode schema for LazyFrame.explode() (#19860)
Ensure List element truncation ellipses respect ASCII* table formats (#19835)
Validate subnodes in validate IR (#19831)
Raise if merge non-global categoricals in unpivot (#19826)
Type hints for window_size incorrectly included timedelta in some rolling functions (#19827)
Don't panic if column not found (#19824)
Fix gather of Scalar null + idx w/ validity (#19823)
Fix object chunked gather (#19811)
Fix inconsistency between code and comment (#19810)
Fix filter scalar nulls (#19786)
Altair tooltip was being incorrectly applied to plots which did not accept it (#19789)
Fix scanning google cloud with service account credentials file (#19782)
Fix incorrect filter after right-join on LazyFrame (#19775)
Fix incorrect lazy schema for explode on array columns (#19776)
Fix incorrect lazy schema for aggregations (#19753)
Fix validation for inner and left join when join_nulls unflaged (#19698)
SQL ELSE clause should be implicitly NULL when omitted (#19714)
In group_by_dynamic, period and every were getting applied in reverse order for the window upper boundary (#19706)
Only allow list.to_struct to be elementwise when width is fixed (#19688)
Make Array arithmetic ops fully elementwise (#19682)
Update line-splitting logic in batched CSV reader (#19508)
Fix incorrect lazy schema for explode() in agg() (#19629)
Fix filter incorrectly pushed past struct unnest when unnested column name matches upper column name (#19638)
Ensure mean_horizontal raises on non-numeric input (#19648)
Reorder conditions in is_leap_year (#19602)
Copy height in .vstack() for empty dataframes (#19641) (#19642)
Run join type coercion with correct schemas active (#19625)
Correct wildcard and input expansion for some more functions (#19588)
Allow .struct.with_fields inside list.eval (#19617)
Sortedness was incorrectly being preserved in dt.offset_by when offsetting by non-constant durations in the timezone-naive case (#19616)
Fix incorrect scan_parquet().with_row_index() with non-zero slice or with streaming collect (#19609)
Fix mask and validity confusion in Parquet String decoding (#19614)
Parquet decoding of nested dictionary values (#19605)
Do not attempt to load default credentials when credential_provider is given (#19589)
Fix gather len in group-by state (#19586)
Added input validation for explode operation in the array namespace (#19163)
Improve error message (#19546)
Fix predicate pushdown into inequality joins (#19582)

📖 Documentation

Add more Rust examples to User Guide (#20194)
Expand plotting docs (#19719)
Fix Rust examples in user guide (#20075)
Update by param description for rolling_*_by functions (#19715)
Fix inconsistency between code and comment (#20070)
Correct supported compression formats (#20085)
Specify strictness in cast (#20067)
Fix broken links to user guide (#19989)
Minor doc fixes and cleanup (#19935)
Complete parameters description and add an example for clip() (#19875)
Fix some warnings during docs build (#19848)
Change dprint config (#19747)
Fix formatting of nested list (#19746)
Add meta.is_column to API docs (#19744)
Fix join API reference links (#19745)
Revise and rework user-guide/expressions (#19360)
Update Excel page of user guide to refer to fastexcel as the default engine (#19691)
Alter examples for round_sig_figs to make behaviour clearer (#19667)
Assorted fixes to Rust API docs (#19664)
Improve replace and replace_all docstring explanation of the "$" character with reference to capture groups (vs use as a literal) (#19529)

📦 Build system

Upgrade sqlparser-rs from version 0.49 to 0.52 (#20110)
Bump memmap2 to version 0.9 (#20105)
Bump object_store to version 0.11 (#20102)
Bump fs4 to version 0.12 (#20101)
Fix path to polars-dylib crate in workspace (#20103)
Bump thiserror to version 2 (#20097)
Bump atoi_simd to version 0.16 (#20098)
Bump chrono-tz to 0.10 (#20094)
Update Rust dependency ndarray to 0.16 (#20093)
Bump Rust toolchain to nightly-2024-11-28 (#20064)
Pin maturin (#20063)
Use public windows runners in python release (#19982)
Add windows-aarch64 to python binaries (#19966)

🛠️ Other improvements

Deprecate ddof parameter for correlation coefficient (#20197)
Move Bitwise aggregations to FunctionExpr (#20193)
Add ragged lines test (#20182)
Remove dedicated sink_(parquet/ipc)_cloud functions (#20164)
Move new-streaming parquet and CSV sources to under io_sources/ (#20160)
Move horizontal methods to polars-ops (#20134)
Remove useless SeriesTrait::get implementations (#20136)
Add a bunch more automated row encoding sortedness tests (#20056)
Replace custom PushNode trait with Extend (#20107)
Update AWS doc dependencies (#20095)
Move cast from polars-arrow to polars-compute (#19967)
Implement nested row encoding / decoding (#19874)
Remove use of cast in ArrowArray::new (#19899)
Switch back to PyO3 0.22 (#19851)
Make chunked gathers generic over chunk bit width (#19856)
Add proper tests for row encoding (#19843)
Add ToField context for common args (#19833)
Add new streaming CSV source (#19694)
Add BytesIndexMap and use in RowEncodedHashGrouper (#19817)
Use HashKeys abstraction (#19785)
Migrate polars-expr AggregationContext to use Column (#19736)
Add InMemoryJoin to new-streaming engine (#19741)
Use Column for the {try,}_apply_columns{_par,} functions on DataFrame (#19683)
Remove more @scalar-opt (#19666)
Move Series bitops to std::ops::Bit... (#19673)
Mark test_parquet.py test_dict_slices as slow (#19675)
Get Column into polars-expr (#19660)
Remove unused file (#19661)
Delegate feature flags for polars-stream (#19659)
Streamline internal SQL join condition processing (#19658)
Factor out logic for re-use by new streaming CSV source (#19637)
Configure grouped Dependabot updates (#19604)
Share source token between all sender tasks of source nodes in new-streaming engine (#19593)
Fix PyO3 error in CI (#19545)
Update nightly compiler version (#19590)
Added input validation for explode operation in the array namespace (#19163)
Remove MutableStructArray (#19587)
Fix lint (#19584)
Add a Column::Partitioned variant (#19557)
Move to fast-float2 (#19578)
Only run remote bench on rust changes (#19581)

Thank you to all our contributors for making this release possible! @3tilley, @DzenanJupic, @MarcoGorelli, @TNieuwdorp, @YichiZhang0613, @alexander-beedie, @barak1412, @braaannigan, @cmdlineluser, @coastalwhite, @corwinjoy, @dependabot, @dependabot[bot], @eitsupi, @engylemure, @etiennebacher, @flowlight0, @gab23r, @henryharbeck, @iharthi, @iliya-malecki, @ion-elgreco, @itamarst, @jackxxu, @janpipek, @jqnatividad, @letkemann, @lukapeschke, @lukemanley, @max-muoto, @mcrumiller, @mhogervo, @nameexhaustion, @orlp, @ptiza, @ritchie46, @rodrigogiraoserrao, @siddharth-vi, @sn0rkmaiden, @stijnherfst, @stinodego, @wence- and @wsyxbcl