Use BitmapBuilder in yet more places (#20868)
Make an owned version of append (#20800)
Use BitmapBuilder in a lot more places (#20776)
Extend functionality on BitmapBuilder and use in Growables (#20754)
Specialize first/last agg for simple types in new-streaming engine (#20728)
Improve state caching and parallelism of window functions (#20689)
Broadcast without materialization in concat_arr (#20681)
Cache rolling groups (#20675)
Use downcast_ref instead of dtype equality in <dyn SeriesTrait as AsRef<ChunkedArray<T>> (#20664)
Fix performance regression for DataFrame serialization/pickling (#20641)
Make Parquet verify_dict_indices SIMD (#20623)
Move to zlib-rs by default and use zstd::with_buffer (#20614)
Skip filter expansion in eager (#20586)
Use AtomicWaker in async engine task joiner (#20604)
Move morsel distribution to the computational async engine (#20600)
Improve unique pred-pd (#20569)
Collapse expanded filters in eager (#20493)
Remove predicate from IR::DataFrame (#20492)
Add proper distributor to new-streaming parquet reader (#20372)
Use different binview dedup strategy depending on chunks ratio (#20451)
Generalize the arg_sort fast path onto Column (#20437)
Dedup binviews up front (#20449)
Re-enable common subplan elim for new-streaming engine (#20443)
Don't collect all LHS arrays in gather (#20441)
Remove prepare_series for gather kernels (#20439)
Don't always take all data buffers when gathering views (#20435)
Order observability optimizations (#20396)
Purge ChunkedArray Metadata (#20371)
Drop probe tables in parallel in new-streaming equi-join (#20373)
Explicit transpose in new-streaming equi-join finalize (#20363)
Cache dtype on ExprIR (#20331)

✨ Enhancements

Expose descending and nulls last in window order-by (#20919)
Add linear_space (#20678)
Implement df.unique() on new-streaming engine (#20875)
Add unique operations for Decimal dtype (#20855)
Add NDJson sink for the new streaming engine (#20805)
Support nested keys in window functions (#20837)
Add CSV sink for the new streaming engine (#20804)
Periodically check python signals ('CTRL-C' handling) (#20826)
Experimental unity catalog client (#20798)
Support cumulative aggregations for Decimal dtype (#20802)
Improve window function caching strategy (#20791)
Allow different python versions for pickle (#20740)
Add SQL support for the NORMALIZE string function (#20705)
Add 'allow_exact_matches' join_asof' (#20723)
Add new-streaming first/last aggregations (#20716)
Add Parquet Sink to new streaming engine (#20690)
Expose IRBuilder (#20710)
Make automatic use of Azure storage account keys opt-in (#20652)
Improve GroupsProxy/GroupsPosition to be sliceable and cheaply cloneable (#20673)
Add str.normalize() (#20483)
Allow more group_by agg expressions in the new streaming engine (#20663)
Support writing partitioned parquet to cloud (#20590)
Add hint to error message for extra struct field in JSON (#20612)
Add index_of() function to Series and Expr (#19894)
Update sqlparser-rs, enabling "LEFT" keyword to be optional for anti/semi joins in SQL queries (#20576)
Add cat.starts_with/cat.ends_with (#20257)
Add Int128 IO support for csv & ipc (#20535)
Support arbitrary expressions in 'join_where' (#20525)
Allow more join lossless casting (#20474)
Always resolve dynamic types in schema (#20406)
Order observability optimizations (#20396)
Add FirstArgLossless supertype (#20394)
Add dt.replace (#19708)
Polars build for Pyodide (#20383)
Add Azure credential provider using DefaultAzureCredential() (#20384)
Add env var to ignore file cache allocate error (#20356)
Enable joins between compatible differing numeric key columns (#20332)
Cache dtype on ExprIR (#20331)
Serialize DataFrame/Series using IPC in serde (#20266)
Improve error message on SchemaError (#20326)
Use better error messages when opening files (#20307)
Add 'skip_lines' for CSV (#20301)
Allow subtraction of time dtype columns (#20300)
Add bin.reinterpret (#20263)
Allow decoding of non-Polars arrow dictionaries in Arrow and Parquet (#20248)
Add new Int128Type (#20232)
IR formatting QoL improvements (#20246)
Add cat.len_chars and cat.len_bytes (#20211)
Expose AexprArena (#20230)

🐞 Bug fixes

Fix from_numpy returning Null dtype for empty 1D numpy array (#20907)
Fix map_elements panicking with Decimal type (#20905)
Warn if asof keys not sorted (#20887)
Avoid name collisions and panicking in object conversion (#20890)
Incorrect scale used in log and exp for Decimal type (#20888)
Don't deep clone manuallydrop in GroupsPosition (#20886)
Fix DuplicateError when selecting columns after join_where or cross join + filter (#20865)
Incorrect Decimal value for fill_null(strategy="one") (#20844)
Fix one edge case (out of many) of int128 literals not working (#20830)
Add height check to frame-level row indexing when key is int (#20778)
Remove assert that panics on group_by followed by head(n), where n is larger then the frame height (#20819)
Fix panic InvalidHeaderValue scanning from S3 on Windows (#20820)
Fix clip for Decimal returning wrong values (#20814)
Incorrect height from slicing after projecting only the file path column (#20817)
Shift mask when skipping Bitpacked values in Parquet (#20810)
Error instead of truncate if length mismatch for several str functions (#20781)
Support cumulative aggregations for Decimal dtype (#20802)
Do not print sensitive information to output on POLARS_VERBOSE (#20797)
Ignore file cache allocation error if fallocate() is not permitted (#20796)
Incorrect logic in assert_series_equal for infinities (#20763)
Avoid blocking on async runtime when resolving cloud scans (#20750)
Fix allow_invalid_certificates being ignored in storage_options (#20744)
Incorrect output type for map_groups returning all-NULL column (#20743)
Fix unique(maintain_order=True) raising InvalidOperationError for null array (#20737)
Don't collapse into a Nested Loop Join if the cross join maintains order (#20729)
Don't serialize credentials provider (#20741)
Fix Series.n_unique raising for list of struct (#20724)
Fix incorrect top-k by sorted column, fix head() returning extra rows (#20722)
Add outer validity to AnyValueBufferTrusted for structs (#20713)
Don't partition group-by with non-scalar literals in agg (#20704)
Incorrect view buffer dedup (#20691)
Only verify Parquet ConvertedType if no LogicalType is given (#20682)
Validate length of schema_overrides in read_csv (#20672)
Fix map_elements ignoring skip_nulls=True for struct dtype (#20668)
Check for MAP-GROUPS in cloud-eligible (#20662)
Fix empty output of to_arrow() on filtered unit height DataFrame (#20656)
Add .default to azure credential provider scope URL (#20651)
Fix join_asof panicking for invalid tolerance input (#20643)
Incorrect flag check on is_elementwise (#20646)
Don't panic but set null type if type is unknown (#20647)
Fix performance regression for DataFrame serialization/pickling (#20641)
Fix Int128 dtype serialization (#20629)
Ensure that SQL LIKE and ILIKE operators support multi-line matches (#20613)
Properly broadcast in sort_by (#20434)
Properly load nested Parquet Statistics (#20610)
AWS environment config was not loaded when credential provider was used (#20611)
Fix order observability of group-by-dyn (#20615)
Soundness when loading Parquet string statistics (#20585)
Fix error filtering after with_columns() on unit height LazyFrame (#20584)
Restore symbols on Apple by bumping nightly version (#20563)
Fix variable name in error message for "unsupported data type" in rolling and upsampling operations (#20553)
Output index type instead of u32 for sum_horizontal with boolean inputs (#20531)
Fix more global categorical issues (#20547)
Update eager join doctest on multiple columns (#20542)
Revert categorical unique code (#20540)
Add unique fast path for empty categoricals (#20536)
Fix various Int128 operations (#20515)
Fix global cat unique (#20524)
Fix union (#20523)
Fix rolling aggregations for various integer types (#20512)
Ensure ignore_nulls is respected in horizontal sum/mean (#20469)
Fix incorrectly added sorted flag after append for lexically ordered categorical series (#20414)
More Int128 testing and related fixes (#20494)
Validate column names in unique() for empty DataFrames (#20411)
Implement list.min and list.max for list[i128] (#20488)
Decimal from physical in horizontal min/max and shift (#20487)
Don't remove sort if first/last strategy is set in unique (#20481)
Fix join literal behavior (#20477)
Validate asof join by args in IR resolving phase (#20473)
Fix align_frames with single row panicking (#20466)
Allow multiple column sort for Decimal (#20452)
Fix mode panicking for String dtype (#20458)
Return correct schema for sum_horizontal with boolean dtype (#20459)
Properly handle to_physical_repr of nested types (#20413)
Workaround for mmap crash under Emscripten (#20418)
Fix using new_columns in scan_csv with compressed file (#20412)
Fix decimal arithmetic schema (#20398)
Raise on categorical search_sorted (#20395)
Don't try to load non-existend List/FSL statistics (#20388)
Propagate nulls for float methods on all numeric types (#20386)
Add env var to ignore file cache allocate error (#20356)
Flip order on right join (#20358)
Fix incorrect object store caching for ADLS URI (#20357)
Use the same encoding for nullable as non-nullable arrays (#20323)
Improve error message on SchemaError (#20326)
Boolean optional slice pushdown (#20315)
Properly handle from_physical for List/Array (#20311)
Ignore quotes in csv comments (#20306)
Ensure pl.datetime returns empty column when input columns are empty (#20278)
Ensure output height does not change on lazy projection pushdown with aggregations (#20223)
Fix error writing on Windows to locations outside of C drive (#20245)
Incorrect comparison in some cases with filtered list/array columns (#20243)
Ensure height is maintained in SQL SELECT 1 FROM (#20241)
Properly account for updated Categorical in .unique() kernel (#20235)
Fix incorrect lazy select(len()) with some select orderings (#20222)
Fix assertion panic on LazyFrame scratch.is_empty() (#20219)

📖 Documentation

Update source URL for legislators-historical.csv (#20858)
Fix typo in sql functions (cosinus -> cosine) (#20676)
Fix small typo in plugins (polars-dt -> polars-st) (#20657)
Add polars-h3 and polars-st to plugin list (#20653)
Add docs reference for Field (#20625)
Miscellaneous minor updates/fixes (#20573)
Update "group_by_rolling" (deprecated) to "rolling" in user guide (#20548)
Fix flaky doctests (#20516)
Clarify the join pre-condition of join_asof (#20509)
Fix Expr.all description of Kleene logic (#20409)
Improve docstring clarity (#20416)
Fix "forcolumnar" typo in docs (#20401)
Remove Plugins overview page without information (#20348)
Small fixes/clarifications in user guide (#20335)
Improve docs about NaN (#20310)
Fix typo in fork warning (#20258)

🛠️ Other improvements

Add tests for already resolved issues (#20921)
Fix the verify_dict_indices codegen (#20920)
Add ProjectionContext in projection pushdown opt (#20918)
Disable 'catalog' in build (#20897)
Implement negative slice for new streaming IPC (#20866)
Remove last instances of itoa (#20881)
Reduce bloat in static_array_collect by using BitmapBuilders (#20891)
Use defunctionalization in polars-core scalar.rs in order to reduce code duplication (#20377)
Simplify decimal formatting and remove itoap dep (#20880)
Remove polars(_core)::export (#20869)
Debloat Series bitops (#20873)
Move sum kernel to polars-compute (#20867)
Remove todo and test restriction for new-streaming (#20861)
Dispatch to the in-mem engine for AExpr::Gather (#20862)
Dispatch to the in-memory engine for multifile sources (#20860)
Add tests for open issues (#20857)
Mark 'register_startup' as unsafe (#20841)
Reduce mode bloat (#20839)
Rename ContainsMany to ContainsAny (#20785)
Unpin NumPy in type checking workflow (#20792)
Add various tests (#20768)
Small drive-by's (#20772)
Touch the upload probe for the remote benchmark (#20767)
Fix remote benchmark script (#20755)
Fix tests (#20745)
Simplify hive predicate handling in NEW_MULTIFILE (#20730)
Add tests for various open issues (#20720)
Add tests for various open issues that have been fixed (#20680)
Don't include debug symbols in benchmark run (#20571)
Remove implicit reverse from AExpr::replace_inputs() (#20659)
Implement CSV, IPC and NDJson in the MultiScanExec node (#20648)
Fix Python deps installation in remote-benchmark workflow (#20619)
Fix rust-analyzer misinterpretation (#20595)
Remove unused file (#20594)
Rename is_numeric to is_primitive_numeric (#20574)
Reduce size of ArrowDataType by boxing heavy variants (#20588)
Bump multiversion from 0.7 to 0.8 (#20543)
Groundwork for allowing multi-output nodes in the new streaming engine (#20550)
Improve bin size info (#20551)
Increase categorical test coverage (#20514)
Report wheel sizes (#20541)
Add tests for floor/ceil on integers (#20479)
Expose and rewrite 'can_pre_agg' (#20450)
Skip test on windows; kuzu import segfaults (#20463)
Add a TypeCheckRule to the optimizer (#20425)
Fix duplicate cols in new-streaming parquet prefilter (#20419)
Move gather kernels to polars-compute (#20415)
Temporarily disable common subplan elim for new-streaming (#20374)
Remove unused IR::Reduce node (#20392)
Enable masked out list, struct and array elements in parametric tests (#20365)
Dispatch slice/filter lowering properly (#20390)
Move hive partitioning/multi-file handling outside of readers (#20203)
Purge ChunkedArray Metadata (#20371)
Add equi joins to new streaming engine (#19869)
Make parametric tests include pl.List and pl.Array by default (#20319)
Use Column in Row Encoding (#20312)
Don't warn on fork hook (#20309)
Don't deconstruct CsvParseOptions (#20302)
Allow decoding of non-Polars arrow dictionaries in Arrow and Parquet (#20248)
Add FunctionCastOptions and conservative IR-level cast type-checking (#20286)
Add more descriptive error message for failure of vstack/extend (#20299)
Expose AexprArena (#20230)

Thank you to all our contributors for making this release possible! @Biswas-N, @FBruzzesi, @IndexSeek, @Jesse-Bakker, @MarcoGorelli, @MoizesCBF, @Prathamesh-Ghatole, @SamuelAllain, @Terrigible, @ZemanOndrej, @alexander-beedie, @arnabanimesh, @balbok0, @beckernick, @braaannigan, @brifitz, @bschoenmaeckers, @burakemir, @coastalwhite, @deanm0000, @dependabot[bot], @dimfeld, @eitsupi, @etiennebacher, @georgestagg, @hamdanal, @haocheng6, @ion-elgreco, @itamarst, @jqnatividad, @kszlim, @lukemanley, @mcrumiller, @nameexhaustion, @noexecstack, @orlp, @ptiza, @r-brink, @ritchie46, @rodrigogiraoserrao, @siddharth-vi, @stijnherfst, @stinodego, @tswast, @zero-stroke and dependabot[bot]