Address inadvertent quadratic behaviour in expand_columns (#19469)
Move rolling_corr/cov to an actual implementation on Series (#19466)
Don't split par if cast to categorical (#19462)
Improve var/cov/corr performance (#19381)
Reduce memcopy in parquet (#19350)
Optimize array and list gather (#19327)
Add/fix unordered row decode, change unordered format (#19284)
Fast decision for Parquet dictionary encoding (#19256)
Make date_range / datetime_range ~10x faster for constant durations (#19216)
Batch utf8-validation in csv 18% / 25% on 1.9.0 (#19124)
Use two-pass algorithm for csv to ensure correctness and SIMDize more ~17% (#19088)
Use List's TotalEqKernel (#18984)
Improve rename performace for Lazy API (#18890)
Collapse cross-joins to faster joins (#18633)
Cache register plugin function (#18860)

✨ Enhancements

Implement nested Parquet writing for High-Precision Decimals (#19476)
Improve read_database typing (#19444)
Add IPC sink in new streaming engine (#19431)
Added escape_regex operation to the str namespace and as a global function (#19257)
Add SQL support for bit_count and bitwise &, |, and xor operators (#19114)
Add credential provider utility classes for AWS, GCP (#19297)
Support decoding Float16 in Parquet (#19278)
Experimental credential_provider argument for scan_parquet (#19271)
Allow DeltaTable input to scan_delta and read_delta (#19229)
Make FlightConsumer Send and support compressed data (#19262)
New quantile interpolation method & QUANTILE_DISC function in SQL (#19139)
Conserve Parquet SortingColumns for ints (#19251)
Low level flight interface (#19239)
Improved list arithmetic support (#19162)
Expose LTS CPU in show_versions() (#19193)
Check Python version when deserializing UDFs (#19175)
Quantile function in SQL (#18047)
Improve scalar strict message (#19117)
Add Series::{first, last, approx_n_unique} (#19093)
Allow for rolling_*_by to use index count as window (#19071)
Delay deserialization of python function until physical plan (#19069)
Add cum(_min/_max) for pl.Boolean (#19061)
Bitwise operations / aggregations (#18994)
Improved error message DSL -> IR resolving (#19032)
Add strict param to eager/lazy frame "rename" (#19017)
Support schema arg in read/scan_parquet() (#19013)
Add allow_missing_columns option to read/scan_parquet (#18922)
Use FFI to extract Series from different Polars binaries (#18964)
Allow for zero-width fixed size lists (#18940)
Improve scalar strict message (#18904)
Support arithmetic between Series with dtype list (#17823)
Relaxed schema alignment for parquet file list read (#18803)
Always preserve sorted flag for .dt.date (#18692)
Implement single inequality joins for join_where (#18727)

🐞 Bug fixes

Include Array in to_physical (#19474)
Don't panic in SQL temporal string check; raise suitable ColumnNotFound error (#19473)
Properly raise on mean_horizontal with wrong dtypes (#19472)
Make output dtype known for list.to_struct when fields are passed (#19439)
Address inadvertent quadratic behaviour in expand_columns (#19469)
Ensure sorted flag is unset after Int->String cast (#19470)
Fix row_index of batched reader (#19465)
Fix perfect groupby (#19461)
Correct wildcard expansion for functions (#19449)
Ensure struct eq/ne_missing also compares outer validity (#19443)
Fix incorrect reverse on struct containing NULLs (#19446)
Faulty escape_regex example (#19440)
Capture groups should be ignored in replace when literal=True (#19413)
Fix ColumnNotFound when using pl.element() inside list.eval (#19438)
Updates error message in csv parser to recommend schema_overrides instead of deprecated dtypes argument (#19416)
Incorrect .join(..., how="left").head(N) if N <= left_df.height() and there are duplicate matches (#19422)
Support Array type in more DataType methods (#19427)
Bug in group_tuples_perfect, tail was not processed properly (#19417)
Ensure that ASCII* table formats do not use the UTF8 ellipsis char when truncating rows/cols/values (#19404)
Allow .get(null) in groupby context (#19401)
Fix include_file_paths and with_row_index for streaming CSV scan (#19394)
Flaky parametric parquet test (#19393)
Raise on data mismatch in str.json_decode (#19347)
Fix unsoundness in group_tuples_perfect (#19359)
Ensure Python version matches version used to serialize credential provider (#19375)
Capture groups should be ignored in replace_all when literal=True (#19366)
Ignore Parquet is_{min,max}_value_exact when set to true (#19344)
Projection pushdown was ignored by include_file_paths (#19341)
Don't produce duplicate column names in Series.to_dummies (#19326)
Use of HAVING outside of GROUP BY should raise a suitable SQLSyntaxError (#19320)
Fix empty array gather (#19316)
Merge categorical rev-map in unpivot (#19313)
DataFrame descending sorting by single list element (#19233)
Fix cse union schema (#19305)
Correctly load Parquet statistics for f16 (#19296)
Error on invalid query (#19303)
Fix enum scalar output (#19301)
Fix list gather invalid fast path (#19299)
Fix quoting style of decimal csv output (#19298)
Don't vertically parallelize literal select (#19295)
Fix struct reshape fast path (#19294)
Also split on forward slashes during hive path inference on Windows (#19282)
Don't cse as_struct (#19280)
Only apply string parsing to String dtype (#19222)
Compilation error missing use JsonLineReader (#19244)
Don't remember Parquet statistics if filtered (#19248)
Do not check dtypes of non-projected columns for parquet (#19254)
Parquet predicate pushdown for lit(_) != (#19246)
Use all chunks in Series from arrow struct (#19218)
Implement is_nested_null for Null Array (#19219)
Fix struct literals (#19214)
Plotting was not interacting well with Altair schema wrappers (#19213)
Fixing infer_schema for DataType::Null (#19201)
Migrate to PyO3 0.22 and released verion of rust-numpy crate (#19199)
Don't unwrap() expansion (#19196)
Properly handle non-nullable nested Parquet (#19192)
Fix invalid list collection in expression engine (#19191)
Implement to_arrow functionality properly for Arrays (#19077)
Fix incorrect (eq|ne)_missing on List/Array types (#19155)
Properly broadcast Struct when then validity (#19148)
Allow partial name overlap in join_where resolution (#19128)
Fix floordiv / modulo with scalar 0 on LHS (#19143)
Ensure aligned chunks in OOC sort (#19118)
Recursively align when converting to ArrowArray (#19097)
Raise on invalid shape of shape 1, empty combination (#19113)
Use two-pass algorithm for csv to ensure correctness and SIMDize more ~17% (#19088)
Allow converting DatetimeOwned to ChunkedArray (#19094)
Throw proper error for empty char params in scan_csv (#19100)
Ensure parquet schema arg is propagated to IR (#19084)
Only rewrite numeric ineq joins (#19083)
Check validity of columns of keys/aggs in dsl->ir (#19082)
Bitwise aggregations should ignore null values (#19067)
Remove failing datetime subclass test (#19068)
Fix ser/de PlSmallStr error (#19060)
Remove failing temporal lit tests (#19056)
Divide-by-zero in OOC sort (#19048)
Ensure must_flush flag is not reset (#19046)
Error node should be on top (#19045)
Force nested struct missing equality (#19031)
Fix invalid alias udf (#19021)
Raise invalid predicate join_where (#19020)
Fix nested flag of functions with multiple arguments (#19016)
Fix projection pushdown bug in IEJOINS (#19015)
Separate temporal tests (#19012)
Return the truth values of ne_missing and eq_missing operations for struct instead of null (#18930)
Fix struct broadcasting comparisons (#19003)
Wrong result on when().then().otherwise() on struct when both result are broadcast (#19000)
Improve literals for temporal subclasses (#18998)
Ensure same fmt in Series/AnyValue to string cast (#18982)
Return correct value for when().then().else() on structs when using first()\last() (#18969)
IPC don't write variadic_buffer_counts in blocks, but only dictionaries (#18980)
Respect allow_threading in TernaryExpr (#18977)
Make join test order-agnostic (#18975)
Window function had incorrect output name on ExprIR (#18970)
Fix lit().shrink_dtype() broadcasting (#18958)
Parallel evaluation of cumulative_eval (#18959)
Properly implement AnyValue::Binary into_py (#18960)
Fix Expr.over with order_by did not take effect if group keys were sorted (#18947)
Properly fetch type of full None List Series (#18916)
Incorrect mode for sorted input (#18945)
Properly choose inner physical type for Array (#18942)
Disable very old date in timezone test for CI (#18935)
Infer reshape dims when determining schema (#18923)
Incorrect broadcasting on list-of-string set ops (#18918)
Adding with_row_index() to previously collected lazy scan does not take effect (#18913)
Properly zip struct validities (#18886)
Ensure ListPrimitiveBuilder dtype invariant is asserted (#18889)
Out-of-bounds gather in categorical->int cast (#18897)
AnyValue Series from Categorical/Enum (#18893)
Properly cast AnyValue string (#18888)
Fix SO in json inference (#18887)
Use proper thread pool in cumulative_eval (#18885)
Properly calculate duration units (#18869)
Check values in strict cast Int to Time (#18854)
Fix typo in DuplicateError error message (#18855)
Properly merge live- and dead columns in prefiltered (#18862)
DataFrame plot was raising when some extra keywords were passed to encodings (e.g. x=alt.X(a, axis=alt.Axis(labelAngle=30))) (#18836)
Respect strictness in list constructor (#18853)
Properly broadcast array arithmetic (#18851)
Throw error for comparison of unequal length series (#18816)
Raise when parquet file has extra columns and no select() was done (#18843)
Replace DynArgs with an enum containing all its variants (#18746)
Return empty DF when input is empty json list (#18827)
Handle AnyValue::Struct to prevent null returns (#18801)
Struct filter by index (#18778)
Proper dtype casting for struct embedded categoricals in chunked categoricals (#18815)
Fixed some error/assertion types (#18811)
Remove panic in arr.to_struct (#18804)
Allow empty sort by columns (#18774)
Broadcast zip_with for structs (#18770)
Dropped/shifted rows in parquet scan with streaming=True (#18766)
Fix cum_max using exception text of cum_min for invalid dtype (#18780)
Fix accidental raise on shape 1 (#18748)

📖 Documentation

Fix docstrings for ATAN2 and ATAN2D SQL functions (#19351)
Tiny correction post dask-expr (#19354)
Remove ecosystem viz section since there is one in misc already (#18408)
Fix typo in custom expressions docs (#19292)
Add SQL docs for new QUANTILE_CONT and QUANTILE_DISC functions (#19272)
Add marimo to ecosystem.md (#19250)
Link to main website from banner (#19177)
Fix example of as_struct (#19116)
Clarify difference between bitwise/logical ops (#19180)
Fix examples/read_csv rust example (#19185)
Add non-equi joins to, and revise, joins docs page (#19127)
Add Series.first,last,approx_n_unique to docs (#19146)
Revise and improve 'Concepts' section (#19087)
Fix example of lazy schema verification (#19059)
Rewrite 'Getting started' page (#19028)
Align dates in DataFrame example with Python (#18491)
Fix is_not_nan description (#18985)
Recommend targetDir for rust-analyzer (#18973)
Typo for IntoDf trait (#18933)
Fix broken user-guide API links (#18872)
Fix minor rogue apostrophes (#18865)
Fix link to issue tracker and code snippet format in GPU docs (#18850)
Refactor docs directory hierarchy (#18773)
Minor improvements to contributing guide (#18777)

📦 Build system

Revert PyO3 version back to 0.21 (#19376)
Bump Rust toolchain to nightly-2024-09-29 (#19006)
Bump simd-json to 0.14 (#18999)

🛠️ Other improvements

Undo conflicting fix (#19463)
Remove code in examples folder in favor of the user guide (#19430)
Add var/std support to new streaming engine (#19406)
Add streaming groupby for reductions (#19291)
Add AlignedBytes types (#19308)
Don't pickle entire python function for object store keying (#19340)
Add extra functionality to SharedStorage (#19361)
Improve error message for Zero-Field Structs with Parquet (#19370)
Add tracking of async task wait time statistics (#19373)
Add capability to transmute to SharedStorage (#19353)
Reduce memcopy in parquet (#19350)
Purge arrow-rs support (#19312)
Use size_of/align_of from prelude (#19311)
Add/fix unordered row decode, change unordered format (#19284)
Trim sliced-out memory from ListArrays in list arithmetic (#19276)
Move from parquet-format-safe to polars-parquet-format (#19275)
Purge unused code (#19267)
Skip flaky test (#19242)
Feature gate for list arithmetic (#19237)
Add more tests for list arithmetic (#19225)
Remove unused IPC async (#19223)
Make get_list_builder infallible (#19217)
Migrate to PyO3 0.22 and released verion of rust-numpy crate (#19199)
Make expression output type known (#19195)
Revert "feat(python): Raise an error when users try to use Polars API in a fork()-without-execve() child (#19149) (#19188)
Zero-Field Structs and DataFrame with Height Property (#19123)
Reduction -> GroupedReduction for the new streaming engine (#19176)
Make pl.repeat part of the IR (#19152)
Workaround for rust-analyzer bug (#19134)
Minor CSV bit twiddle nitpick (#19121)
Use row encoding in asof join (#19125)
Remove deprecated raw_entry_mut in StringCache (#19126)
Clean remove_prefix since python3.9 is now the minimum Python (#19070)
Eliminate some uses of deprecated raw_entry (#19102)
Migrate to hashbrown 0.15 (#19091)
Pin hashbrown to 0.14 until migrated (#19076)
Add new streaming engine to CI (#19051)
Add WithRowIndexNode to new-streaming engine (#19037)
Add buffers to zip heads to reduce contention (#19036)
Fix race condition in DistributorChannel (#19033)
Mark schema arg in read/scan_parquet as unstable (#19018)
Fix new-streaming test_lazy_parquet::test_row_index (#19019)
Preserve scalar in more places (#18898)
Mention allow_missing_columns in error message when column not found (parquet) (#18972)
Fix new-streaming test_lazy_parquet::test_row_index (#18978)
Disable CSE-specific test on new streaming engine (#18971)
Add FixedSizeList equality broadcasting (#18967)
Divide ChunkCompare into Eq and Ineq variants (#18963)
Another set of new-stream test skip/fixes (#18952)
Fix/skip variety of new-streaming tests, cont (#18928)
Fix/skip variety of new-streaming tests (#18924)
Minor new-streaming test fixes (#18891)
Make with_column_unchecked take Column (#18863)
Keep scalar in more places (#18775)
Replace DynArgs with an enum containing all its variants (#18746)
Fix new-streaming test_parquet::test_complex_types (#18829)
Fix zero-length len (#18817)
Add panic to unchecked DataFrame constructors in debug mode (#18807)
Add missing implicit datetime alias in ExprIR (#18809)
Fix topological sort in new streaming engine (#18806)
Fix new-streaming parquet test_row_index_projection_pushdown_18463 (#18805)
Remove short-lived / non-CPU bound task spawns on async executor in new-streaming (#18764)
Fix parquet file metadata is dropped after first DSL->IR conversion (#18789)
Remove extra hashmap construction in new-streaming parquet (#18792)
Fix new-streaming parquet on empty parquet (#18763)
Ensure fallback node gets correct length df even if no columns selected (#18772)
Fix input independence tests in new-streaming engine (#18771)
Make DataFrame a Vec of Column instead of Series (#18664)
Run benchmark on PR labeled 'needs-bench' (#18737)
Add pre-filtered decode to new parquet source (#18715)
Allow polars to pass cargo check on windows (#18672)
Remove unsafe in polars-json deserialize code (#18725)

Thank you to all our contributors for making this release possible! @3ok, @Bidek56, @LukasFolwarczny, @Manishearth, @MarcoGorelli, @Plutone11011, @Rashik-raj, @adamreeve, @aleexharris, @alexander-beedie, @alonme, @balbok0, @barak1412, @beckernick, @benrutter, @bradfordlynch, @cmdlineluser, @coastalwhite, @corleyma, @corwinjoy, @deanm0000, @dependabot, @dependabot[bot], @dvillaveces, @edwinvehmaanpera, @eitsupi, @etrotta, @gab23r, @i64, @itamarst, @janscholten, @jbutterwick, @joelostblom, @kenkoooo, @kgv, @khalidmammadov, @laurentS, @max-muoto, @mcrumiller, @mscolnick, @nameexhaustion, @npielawski, @orlp, @pomo-mondreganto, @r-brink, @ritchie46, @rodrigogiraoserrao, @siddharth-vi, @squnit, @stinodego, @sunadase, @t-ded, @wakabame, @wence-, @wolfgang-noichl and @xhiroga