Python Polars 0.18.3

🚀 Performance improvements

• use row format in streaming join ~15% (#9379)
• row encode buffer reuse (#9371)
• bytes row format for streaming groupby/unique keys >3.5x (#9346)
• push slices down map functions (#9350)

✨ Enhancements

• support all numeric dtypes in serde (#9393)
• allow easy load/save of polars Config options to/from file (#9391)
• ensure part of the plan is streaming if aggregati… (#9387)
• add relaxed concatenation (#9382)
• add sql DROP TABLE (#9355)
• support ternary expressions in streaming (#9343)
• add SQL support for null-aware equality checks (#9332)
• add SQL support for regular expression operators (~, !~, ~*, and !~*) (#9327)
• support // integer floordiv operator in the SQL engine (#9324)

🐞 Bug fixes

• fix bug when comparing series (#9359)
• list zip with (#9367)
• parquet + categorical (#9363)
• respect startby in groupby_dynamic when every is greater than 1d (#9362)
• raise groupby apply on empty frame (#9360)
• raise more informative error on string arguments (#9352)
• Allow for tolerance when comparing nested dtype columns (#9272)
• avoid is_in TypeError with sets of values containing 'None' (#9323)

🛠️ Other improvements

• add top-k test for #9385 (#9388)
• document apply 'return_dtype' requirement (#9361)
• clarify when day of week takes effect in groupby_dynamic (#9342)
• add "if you're coming from pandas" tip to groupby_dynamic (#9336)
• fix string language formatting (#9341)
• add doc entries for eq_missing and ne_missing expressions (#9331)
• fixup options for validate arg in join (#9319)

Thank you to all our contributors for making this release possible!
@0xbe7a, @AnatolyBuga, @MarcoGorelli, @alexander-beedie, @dkrako, @durandtibo, @ritchie46 and @universalmind303

Python Polars 0.18.2

🚀 Performance improvements

• increase streaming groupby spill size from 256 to 10_000 (#9312)
• perf(rust, python) Improve rolling min and max for nonulls (#9277)

✨ Enhancements

• allow use of StringCache object as a function decorator (#9309)
• allow use of Config object as a function decorator (#9307)
• serde for 'to_physical' expr (#9294)

🐞 Bug fixes

• fix rolling weighted mean (#9292)
• fix overly-broad string matching in selectors (#9303)
• fix when loading model data from upcoming pydantic 2.x release (#9296)

🛠️ Other improvements

• fix extraneous indent in examples block (#9297)
• Fix typo in Selectors documentation (#9295)

Thank you to all our contributors for making this release possible!
@alexander-beedie, @magarick, @ritchie46, @stinodego and @thomascamminady

Python Polars 0.18.1

🏆 Highlights

• add dedicated selectors module, consolidating/expanding existing selector capabilities (#9204)

🚀 Performance improvements

• slightly improve n_unique performance (#9286)
• use ciborium in Expression pickling (#9235)

✨ Enhancements

• add join cardinality validation (#9278)
• implement set operations for selector API (#9276)
• keep sorted flag after Expr::truncate (#9275)
• add "sql_expr" function (#9248)
• rewrite correlation functions to expression architecture (#9258)
• keep sorted flag on offset_by (#9253)
• add expression json serde (#9236)
• add intersection primitive for selector API (#9240)
• building blocks for expression expansion sets (#9231)
• Add ddof option to rolling_var and rolling_std (#8957)
• immediately flatten nested unions (#9220)
• Allow empty select/with_columns/groupby (#9205)
• add a datetime selector (#9212)
• support float expression on integers (#9210)
• add dedicated selectors module, consolidating/expanding existing selector capabilities (#9204)
• add binary to list<u8> cast (#9161)
• groupby_dynamic by quarter. (#6842)
• add arr.unique expression (#9159)
• implement explode for DataType::Array (#9157)
• Decimal type: sum, min, max aggregations in select and agg context. (#9135)
• Decimal arithmetic (#9123)
• support decimals as cast types in csv parser (#9121)
• Improve error handling for repeat (#9117)

🐞 Bug fixes

• fix pyarrow dataset literal filter (#9274)
• raise on invalid sort_by (#9262)
• match missing Array and Struct classes in FromPyObject (#9271)
• correct ne/e_missing schema (#9257)
• fix cached reproject offsets (#9254)
• delay opening files in streaming engine (#9251)
• ensure agg(F(lit)) == lit (#9222)
• don't SO on concat(expressions) (#9214)
• df.apply first rechunk (#9211)
• clip window_size to length in rolling_apply (#9209)
• raise error on invalid df.apply return (#9207)
• Handle edge cases of named select input (#9198)
• rolling_apply window_size == len (#9181)
• respect time zone in strptime/to_datetime when exact=False (#9171)
• make null chunking behavior equal to other dtypes (#9176)
• return single numpy array in Array dtype -> numpy (#9164)
• fix regression in boolean nulls comparison (#9142)
• fix struct null_count if fields are null arrays (#9151)
• Fix DataFrame.to_arrow() for 0x0 dataframes (#9144)
• categorical construction from null values (#9145)
• let apply caller determine if length needs to be checked. (#9140)
• struct is_in should upcast numeric types (#9110)
• Restore functionality of name arg for date_range (#9107)
• bubble up dtype when converting from arrow (#9120)

🛠️ Other improvements

• Fix grammar and add periods in Expr.over docs (#9244)
• Update linting for py-polars crate (#9242)
• Deprecate exprs=... input for select/with_columns/agg/struct (#9219)
• Enable parallelization in Python Windows tests (#9232)
• Use pytest tmp_path (#9206)
• Build docs in parallel (#9229)
• Unify Python docs workflows (#9228)
• add docstring to __array__ methods (#8055)
• Update expr parsing util to return PyExpr (#9166)
• update pyo3 requirement from 0.18 to 0.19 (#9155)
• clarify how the windows are formed in the rolling_* functions (#9192)
• stabilise polars importtime check (#9196)
• fix "to_decimal" docstring (#9197)
• note that exact=False is a performance footgun (#9186)
• change decimal inference and argument order (#9133)
• Cache Rust build on main branch (#9130)
• Improve df.clear() docs (#8809)
• Bump maturin to 1.0.1 (#9115)
• Bump lint dependency versions (#9116)

Thank you to all our contributors for making this release possible!
@DeflateAwning, @MarcoGorelli, @alexander-beedie, @ankane, @avimallu, @bfeif, @dependabot, @dependabot[bot], @jonashaag, @josh, @lorentzenchr, @magarick, @ritchie46, @stinodego, @universalmind303 and @zundertj

Python Polars 0.18.0

🏆 Highlights

• Rename list namespace accesor from .arr to .list (#8999)

⚠️ Breaking changes

• propagate null in equality comparisons (#9053)
• formalize implode -> explode relation (#9038)
• Drop subclassing support for DataFrame/LazyFrame (#9008)
• consistently return list of date/datetime from lazy date_range (#8513)
• Default date_range/ones/zeros to eager=False (#9007)
• Rename list namespace accesor from .arr to .list (#8999)
• disallow time zones other than those in zoneinfo.available_timezones() (#8993)
• remove window expression magic (#8992)
• raise error when sorted flag not set (#8994)
• Drop subclassing support for GroupBy (#7746)
• in Series constructor, if inputs are time-zone-aware datetimes, convert to UTC (#8881)
• parse offset-naive date time strings as Timestamp(time_unit), offset-aware datetime strings as Timestamp(time_unit, "UTC"), and remove the utc argument (#8714)
• Remove deprecated tz_aware argument (#8696)

🚀 Performance improvements

• speed up write_csv for time-zone-aware columns (#9093)
• parallelize rolling_window group materialization (#9095)
• elide hot loop in hash joins (#9075)

✨ Enhancements

• conversion from Utf8 to Decimal. (#9090)
• default to checking sortedness in groupby_rolling… (#9063)
• propagate null in equality comparisons (#9053)
• warn if constructing Series with time-zone-aware datetimes (#9058)
• implement apply for rolling/dynamic_groupby (#9049)
• Support more data types in lazy repeat (#9046)
• implement strategy=nearest for join_asof (#9024)
• arr.sum expression (#9041)
• formalize implode -> explode relation (#9038)
• add array namespace and min/max expression (#9032)
• improve error message on row-wise overflow (#9021)
• properly apply slice at UNION level (#9018)
• consistently return list of date/datetime from lazy date_range (#8513)
• Default date_range/ones/zeros to eager=False (#9007)
• disallow time zones other than those in zoneinfo.available_timezones() (#8993)
• raise error when sorted flag not set (#8994)
• in Series constructor, if inputs are time-zone-aware datetimes, convert to UTC (#8881)
• parse offset-naive date time strings as Timestamp(time_unit), offset-aware datetime strings as Timestamp(time_unit, "UTC"), and remove the utc argument (#8714)

🐞 Bug fixes

• rolling_groupy was returning incorrect results when offset was positive (#9082)
• don't underflow on list.tail (#9089)
• fix null/empty in List::take_unchecked (#9074)
• repeat by (#9023)
• raise in to_datetime/strptime if format contains hour but not minute directive (#9044)
• Order of pl.Array arguments in docstring (#9059)
• propagate nulls in broadcasting of order comparisons (#9050)
• Improve read_parquet missing column error message (#8961)
• fix apply with passed date/datetime return_dtype (#9035)
• respect inner type in Array construction (#9020)
• raise error on invalid aggregation (#9013)
• fix fused arithmetic in window functions (#9012)
• don't allow silent init of Series declared as int/temporal with floating point values (#9004)
• deprecate time_unit property from Series (#8990)

🛠️ Other improvements

• Improve expression parsing utils (#9094)
• Refactor expression input parsing util (#9085)
• Organize "as_datatype" functions (#9080)
• Change eager path for repeat (#9048)
• Clean up arange/date_range/time_range (#9027)
• Drop subclassing support for DataFrame/LazyFrame (#9008)
• minor SQLContext docstring cleanups (#9005)
• Rename list namespace accesor from .arr to .list (#8999)
• remove window expression magic (#8992)
• Drop subclassing support for GroupBy (#7746)
• refactor!(python): Remove old deprecated functionality (#8995)
• Remove deprecated tz_aware argument (#8696)

Thank you to all our contributors for making this release possible!
@CloseChoice, @MarcoGorelli, @alexander-beedie, @charliegallop, @jonashaag, @mcrumiller, @raymead, @ritchie46, @sorhawell, @stinodego, @tim-habitat and @universalmind303

Rust Polars 0.30.0

🏆 Highlights

• Rename list namespace accesor from .arr to .list (#8999)
• Array (backed by arrow::FixedSizeList datatype (#8943)

⚠️ Breaking changes

• propagate null in equality comparisons (#9053)
• formalize implode -> explode relation (#9038)
• consistently return list of date/datetime from lazy date_range (#8513)
• Rename list namespace accesor from .arr to .list (#8999)
• disallow time zones other than those in zoneinfo.available_timezones() (#8993)
• remove window expression magic (#8992)
• raise error when sorted flag not set (#8994)
• in Series constructor, if inputs are time-zone-aware datetimes, convert to UTC (#8881)
• parse offset-naive date time strings as Timestamp(time_unit), offset-aware datetime strings as Timestamp(time_unit, "UTC"), and remove the utc argument (#8714)
• Remove deprecated tz_aware argument (#8696)

🚀 Performance improvements

• speed up write_csv for time-zone-aware columns (#9093)
• parallelize rolling_window group materialization (#9095)
• elide hot loop in hash joins (#9075)
• improve list explode perf (#8974)
• Improve explodes: offsets_to_indexes performance (#8964)
• avoid quadratic exclude behaviour when selecting against dtypes and/or wildcards (#8953)
• use simd-json for all json parsing (#8922)
• improve json_extract (#8858)
• add optimizer passes and change initial order (#8811)
• fused multiply sub / sub multiply (#8799)
• improve parallel work distribution of sort expression ~4x (#8775)
• change default row-group size (#8758)

✨ Enhancements

• conversion from Utf8 to Decimal. (#9090)
• default to checking sortedness in groupby_rolling… (#9063)
• propagate null in equality comparisons (#9053)
• implement apply for rolling/dynamic_groupby (#9049)
• implement strategy=nearest for join_asof (#9024)
• arr.sum expression (#9041)
• formalize implode -> explode relation (#9038)
• add array namespace and min/max expression (#9032)
• improve error message on row-wise overflow (#9021)
• properly apply slice at UNION level (#9018)
• consistently return list of date/datetime from lazy date_range (#8513)
• disallow time zones other than those in zoneinfo.available_timezones() (#8993)
• raise error when sorted flag not set (#8994)
• in Series constructor, if inputs are time-zone-aware datetimes, convert to UTC (#8881)
• parse offset-naive date time strings as Timestamp(time_unit), offset-aware datetime strings as Timestamp(time_unit, "UTC"), and remove the utc argument (#8714)
• error on invalid sortby expr (#8986)
• Pushdown is_in to pyarrow dataset (#8930)
• Array (backed by arrow::FixedSizeList datatype (#8943)
• multiple enhancements for SQLContext (#8944)
• add sql UNION, UNION ALL & UNION DISTINCT (#8936)
• add sql compound identifiers (#8934)
• add sql EXCLUDE (#8913)
• add sql CASE (#8911)
• add sql EXPLAIN (#8897)
• improve json_extract (#8858)
• add support for sql DISTINCT ON (#8824)
• add LazyFrame null_count (#8837)
• check categorical cache on transpose (#8836)
• add support for OFFSET keyword in SQL queries (#8833)
• add a new time_range utility function (#8776)
• Add hint to use _saturating on overflow (#8805)
• support boolean addition (#8778)
• improved detail in several error messages (#8747)

🐞 Bug fixes

• rolling_groupy was returning incorrect results when offset was positive (#9082)
• fix null/empty in List::take_unchecked (#9074)
• repeat by (#9023)
• raise in to_datetime/strptime if format contains hour but not minute directive (#9044)
• propagate nulls in broadcasting of order comparisons (#9050)
• fix apply with passed date/datetime return_dtype (#9035)
• raise error on invalid aggregation (#9013)
• fix fused arithmetic in window functions (#9012)
• JoinBuilder::force_parallel is modifying allow_parallel (#8617)
• Fix erroneous warning in hist (#8982)
• respect rechunk in parquet (#8935)
• Simplify offsets_to_indexes, fix empty offsets edge cases (#8920)
• sql qualified wildcards (#8916)
• don't check sortedness in asof by (#8906)
• check for object type in csv writer (#8894)
• window function with filtered groups (#8880)
• parse offset-aware strings as UTC in read_csv when try_parse_dates=True (#8864)
• free buffer, but not its contents (#8848)
• improve agg expr field types (#8834)
• sql BETWEEN bounds should be inclusive (#8818)
• sort cached window groups (#8813)
• check null data before take (#8812)
• fix broadcasting on integer bitwise (#8798)
• correct aggregation of overlapping groups (#8794)
• modify join error (#8768)
• don't parallelize sort within rayon job (#8774)
• fix deadlock in cache and improve parallelism/work… (#8765)
• check offset before doing owned mutation (#8760)
• validate data on successful deserialization (#8757)
• improve supertype coercion of functions (#8755)

🛠️ Other improvements

• use concrete type for time zones (#9076)
• factor add_month out of add_impl_month_week_or_day (#9066)
• remove unnecessary timezone trait usage, use concrete type (#9065)
• Fix broken links (#9072)
• bump sqlparser version (#9043)
• move list namespace functions to seperate module (#9040)
• Clean up arange/date_range/time_range (#9027)
• Rename list namespace accesor from .arr to .list (#8999)
• replace pattern match with unwrap (#9000)
• remove window expression magic (#8992)
• Remove deprecated tz_aware argument (#8696)
• simplify take_every (#8971)
• add readmes to all sub crates (#8770)
• refactor(rust); improve arithmetic reuse and don't allocate on binary… (#8781)
• accumulate windows flag during translation (#8773)

Thank you to all our contributors for making this release possible!
@CloseChoice, @MarcoGorelli, @alexander-beedie, @avimallu, @cbowdon, @charliegallop, @chitralverma, @jonashaag, @kpberry, @mcrumiller, @petar-savov, @raymead, @ritchie46, @sorhawell, @stinodego, @tim-habitat, @uchiiii and @universalmind303

Python Polars 0.17.15

🏆 Highlights

• Array (backed by arrow::FixedSizeList datatype (#8943)
• Write dataframes as delta tables (#7616)

🚀 Performance improvements

• improve list explode perf (#8974)
• Improve explodes: offsets_to_indexes performance (#8964)
• avoid quadratic exclude behaviour when selecting against dtypes and/or wildcards (#8953)
• use simd-json for all json parsing (#8922)
• improve performance of align_frames, and add new alignment option (#8899)

✨ Enhancements

• error on invalid sortby expr (#8986)
• Pushdown is_in to pyarrow dataset (#8930)
• allow set column list input to 'drop' and 'drop_nulls' (#8962)
• Array (backed by arrow::FixedSizeList datatype (#8943)
• Add dtype argument for repeat (#8946)
• Use schema keys to define the columns if only the schema is provided to pl.struct (#8952)
• multiple enhancements for SQLContext (#8944)
• add sql UNION, UNION ALL & UNION DISTINCT (#8936)
• add sql compound identifiers (#8934)
• add sql EXCLUDE (#8913)
• add sql CASE (#8911)
• add sql EXPLAIN (#8897)
• Write dataframes as delta tables (#7616)
• improve performance of align_frames, and add new alignment option (#8899)
• improved inference from type annotations (#8895)

🐞 Bug fixes

• Fix erroneous warning in hist (#8982)
• don't modify Series with empty names in-place on DataFrame init (#8956)
• respect rechunk in parquet (#8935)
• Add hint on PyArrow to ADBC import error (#8898)
• Simplify offsets_to_indexes, fix empty offsets edge cases (#8920)
• sql qualified wildcards (#8916)
• address edge cases with in-place modification of Series objects (#8915)
• don't check sortedness in asof by (#8906)
• check for object type in csv writer (#8894)
• improve performance of align_frames, and add new alignment option (#8899)
• window function with filtered groups (#8880)

🛠️ Other improvements

• deprecate rename "in_place" parameter (#8960)
• Clean up tests for repeat (#8979)
• Deprecate name argument for repeat (#8977)
• simplify take_every (#8971)
• Clean up repeat/ones/zeros (#8963)
• further enhance SQLContext docstrings (#8948)
• docs(python) Fix typo in lazygroupby.rs error message (#8937)
• fix docstring for time() (#8939)
• refactor tzinfo-related tests (#8883)

Thank you to all our contributors for making this release possible!
@CloseChoice, @MarcoGorelli, @alexander-beedie, @avimallu, @cbowdon, @chitralverma, @jonashaag, @kpberry, @mcrumiller, @petar-savov, @ritchie46, @stinodego and @universalmind303

Python Polars 0.17.14

🚀 Performance improvements

• optimise align_frames and properly handle the case where the alignment key has duplicate values (#8825)

✨ Enhancements

• add an align option to pl.concat (#8835)
• add support for sql DISTINCT ON (#8824)
• add LazyFrame null_count (#8837)
• check categorical cache on transpose (#8836)
• add support for OFFSET keyword in SQL queries (#8833)
• optimise align_frames and properly handle the case where the alignment key has duplicate values (#8825)

🐞 Bug fixes

• parse offset-aware strings as UTC in read_csv when try_parse_dates=True (#8864)
• handle InitVar typing declarations on dataclass objects (#8856)
• free buffer, but not its contents (#8848)
• improve agg expr field types (#8834)
• optimise align_frames and properly handle the case where the alignment key has duplicate values (#8825)
• sql BETWEEN bounds should be inclusive (#8818)

🛠️ Other improvements

• add examples for Config "set_tbl_formatting" and "set_fmt_str_lengths" methods (#8859)
• Convert between Vec of Series/Pyseries using trait (#8846)

Thank you to all our contributors for making this release possible!
@MarcoGorelli, @alexander-beedie, @ritchie46, @stinodego and @universalmind303

Python Polars 0.17.13

🚀 Performance improvements

• add optimizer passes and change initial order (#8811)
• fused multiply sub / sub multiply (#8799)
• improve parallel work distribution of sort expression ~4x (#8775)
• change default row-group size (#8758)
• elide function calls in AnyValue::eq (#8725)

✨ Enhancements

• add a new time_range utility function (#8776)
• Add hint to use _saturating on overflow (#8805)
• add a "restore_defaults" kwarg to Config init (#8797)
• add lazy time expression (#8785)
• support boolean addition (#8778)
• support SQLContext registration of DataFrames (#8762)
• support automatic SQLContext frame/table registration from local variables (#8749)
• improved detail in several error messages (#8747)
• support frame registration at SQLContext init time, and add an "unregister" method (#8744)
• support repeat for all types (#8741)
• add support for DISTINCT keyword in SQL select clauses (#8740)
• support any day of the week in 'start_by' in groupby_dynamic (#8720)
• add support for USING clause in SQL join operations (#8731)
• add unit tests for extend_constant Expr (#8734)
• add clean multi-frame registration to SQLContext (#8724)
• add support for HAVING clause to SQL GROUP BY operations (#8704)
• improved numpy string interop (#8703)

🐞 Bug fixes

• sort cached window groups (#8813)
• check null data before take (#8812)
• fix broadcasting on integer bitwise (#8798)
• Fix incorrect type hint for arange (#8796)
• correct aggregation of overlapping groups (#8794)
• don't parallelize sort within rayon job (#8774)
• fix deadlock in cache and improve parallelism/work… (#8765)
• check offset before doing owned mutation (#8760)
• don't persist temporary column in disjoint calls to update (#8763)
• validate data on successful deserialization (#8757)
• improve supertype coercion of functions (#8755)
• groupby_dynamic was unnecessarily failing on ambiguous local datetime (#8737)
• ensure count aggregation has proper length when spilling (#8735)
• fix return value of std for single-element sequence with ddof=1 (#8730)
• don't take logical plan during streaming fmt (#8711)
• Don't upcast in round() for f32 when decimal is 0 (#8706)

🛠️ Other improvements

• add entry for lazy time func (#8786)
• add unit tests for extend_constant Expr (#8734)
• add rounding coverage for 32/64 bit floats (#8715)
• Add warning to count methods on null (#8698)

Thank you to all our contributors for making this release possible!
@DeflateAwning, @MarcoGorelli, @alexander-beedie, @mcrumiller, @ritchie46, @stinodego, @uchiiii, @universalmind303 and @zundertj

Rust Polars 0.29.0

🏆 Highlights

• Out-of-core unique (#8573)

⚠️ Breaking changes

• Rename concat_lst to concat_list (#8597)
• Schema improvements (#8286)
• don't create duplicate pivot names (#8002)
• rename toggle_string_cache to enable_string_cache (#7970)
• change top_k(descending) -> bottom_k (#7969)
• in sort, top_k, sort_by, and arg_sort_by, raise if descending is a sequence and its length doesn't match the number of columns to sort by (#7957)

🚀 Performance improvements

• elide function calls in AnyValue::eq (#8725)
• add fused multiply add optimization for expressions (#8690)
• use expression for dot product (#8686)
• improve nested grouptuples related code (#8618)
• buffer spill partitions in ooc sort. ~10/20% (#8616)
• improve OOC sort performance during partition phase (#8590)
• remove some unnecessary calls and matches (#8490)
• less naive count (#8473)
• parallelize almost all flattens (#8468)
• optimize horizontal min/max (#8463)
• reinstate old behavior in numeric group-tuples (#8445)
• remove false sharing in perfect hash table >2x (#8432)
• further optimised conversions to python date/datetime (#8417)
• optimize join inner materialization of single keys (#8405)
• parallelize sorted group tuple materialization (#8387)
• improve materialization of huge cardinality group tuples (#8382)
• improve group_tuples materialization (#8375)
• use online variance kernel for aggregation (#8306)
• add specialized boolean aggregation for min/max (#8294)
• fail fast on non-inferable strings in strptime if no fmt is provided (#8111)
• make chunks search more resilient (#8229)
• SIMD accelerated arg_min/arg_max (via argminmax) (#8074)
• speed up csv parsing for slower datetimes formats (#8213)
• arr.eval run on groupby expression engine when possible (#8199)
• FromParalleIter<Option<str>> for Utf8Chunked ~1.9x (#8058)
• speed up from_par_iter Option<bool> ~2.5x (#8057)
• parallelize numeric ChunkedArray materialization ~2x. (#8053)
• parallelize into_groups materialization ~-25% (#8036)
• use a trusted anyvalue builder (#8001)
• numeric grouptuples with nulls hash in single pass ~25% (#7980)
• use perfect hash table for categoricals (#7951)
• improve group_tuples of high cardinality data ~10% (#7938)
• use streaming instead of partitioned groupby (#7907)
• don't auto-stream groupby (#7906)
• rechunk before aggs (#7903)
• don't re-allocate groups in sorted to_dummies (#7897)

✨ Enhancements

• add support for DISTINCT keyword in SQL select clauses (#8740)
• support any day of the week in 'start_by' in groupby_dynamic (#8720)
• add support for USING clause in SQL join operations (#8731)
• add support for HAVING clause to SQL GROUP BY operations (#8704)
• streaming unions (#8676)
• expression cache (#8674)
• rolling covariance and correlation (#8671)
• Add dt.to_string alias for dt.strftime (#8290)
• use temp dir for ooc spills (#8614)
• make ooc-sort resilient against chunk_size (#8588)
• Set strptime default strict/exact=true (#8587)
• Out-of-core unique (#8573)
• Add to_date, to_datetime, to_time to String namespace (#8579)
• more detailed error message on failure to cast List dtype (#8583)
• don't trigger unreachable code if no dtype is set (#8532)
• accept expressions in groupby_dynamic/rolling (#8528)
• expose quantile/mean for duration (#8491)
• require explicitly sorted flag for upsample (#8488)
• allow for _saturating suffix in duration strings (#8479)
• let duration string accept "1mo_saturating" (#8469)
• add dt.month_start and dt.month_end (#8435)
• add SQL support for cumulative functions (#8457)
• add str_slice method to StringNameSpace (#8427)
• allow negative 'arange' expression (#8413)
• warn if argument is not explicitly sorted (#8409)
• Schema improvements (#8286)
• add support for SQL "IN" expr (#8396)
• cli output mode & sql read_json (#8336)
• rename 'csv-file' to 'csv' (#8101)
• preserve time zone in combine (#8263)
• add use_earliest argument to replace_time_zone for dealing with ambiguous datetimes (#8087)
• SQL CTE's (#8208)
• add duration cumsum and remainder (#8219)
• better algorithm for streaming unique (#8003)
• Add approx distinct count via approx_unique() (#7937)
• adopt FunctionExpr for cat namespace (#8173)
• DatetimeArgs ergonomics (#8133)
• Remove Seek constraint from IpcStreamReader and SerReader (#8166)
• implement FunctionExpr for bound and round methods (#8172)
• display skipped row if same number of rows (#8170)
• move all boolean expressions into BooleanFunction enum (#8132)
• rewrite log expressions to make them serializable (#8126)
• make unique expr serde and cmp (#8153)
• adopt FunctionExpr for abs to allow for serialization (#8129)
• adopt FunctionExpr for cum* functions (#8130)
• support negative index in pct_change (#8137)
• add log1p to list of mathematical functions (#8102)
• expand list of tz-aware formats which can be auto-inferred (#8085)
• clearer error message if strptime without a fmt specified fails (#8086)
• infer tz-aware formats with try_parse_dates in read_csv (#8084)
• feat(python, rust)! make 'mo' interval raise if the target date does not exist (#8078)
• auto-infer fmt for tz-aware date strings (#7405)
• multiple sql contexts & optional sql highlighting in cli (#8072)
• implement arg_sort for struct dtype (#8051)
• support struct in df.unique (#7976)
• change top_k(descending) -> bottom_k (#7969)
• optimize away nested unions in lp (#7861)
• Add seed argument to rank for random (#7913)
• auto-infer detecting time-zone-awareness of fmt argument in strptime; deprecate tz_aware argument (#7886)
• deal with null values in cut/qcut (#7878)
• support datetime/date subclasses (e.g. FreezeGun) (#7819)

🐞 Bug fixes

• groupby_dynamic was unnecessarily failing on ambiguous local datetime (#8737)
• ensure count aggregation has proper length when spilling (#8735)
• fix return value of std for single-element sequence with ddof=1 (#8730)
• don't take logical plan during streaming fmt (#8711)
• Don't upcast in round() for f32 when decimal is 0 (#8706)
• block predicate containing shifts and windows after sort (#8670)
• ensure perfect hash table processes the nulls (#8668)
• Reading more tiny CSVs than workers in parallel will deadlock (#8441)
• respect maintain_order in partitioned groupby (#8653)
• fix explode null series (#8654)
• fix categorical agg type (#8645)
• allow list<null> -> list<cat> (#8636)
• maintain sorted info on top-k and empty sort (#8615)
• maintain sortedness in date -> datetime cast (#8606)
• fix determining of supertype for tz-aware and tz-naive datetimes (#8585)
• fix csv reader with new line in header (#8580)
• correct for nested offsets in json serialization (#8584)
• fix wrong dtype init in streaming groupby (#8574)
• fix categorical/string_cache fill_null panic (#8562)
• fix window function contention in binary expression (#8544)
• fix StructChunked not_equal comparator/operator (#8547)
• fix struct pyarrow ffi (#8543)
• don't trigger unreachable code if no dtype is set (#8532)
• keep sorted info on agg_first and simple singleton… (#8526)
• unset fast_unique coming from arrow (#8521)
• correct sign-reversed scale on DecimalChunked to Python Decimal conversion (fixes #8423) (#8508)
• don't error on cast if column is not projected (#8495)
• ensure window function succeeds on empty frame (#8492)
• don't set verbose on union (#8487)
• check literal/group length before claiming agg sta… (#8486)
• fix error message of offset_by if offsetting by negative number of months (#8464)
• fix sorted warning (#8462)
• fix features serde and dtype-struct not compiling together (#8439)
• respect dtype in anonymous list builder in case of… (#8428)
• infer supertype in json serde (#8411)
• duration on empty df (#8403)
• don't inadvertently set Series initialised with nested tuple data as Object dtype (#8401)
• use physical in streaming unique global table (#8390)
• recursively bubble up all dtypes in list cast (#8386)
• is_in struct logical types (#8378)
• fix nested null parquet read (#8372)
• fix logical type in ListChunked::new_from_index (#8367)
• bubble up logical type in recursive list cast (#8356)
• implement clone_inner for all series (#8357)
• fix fill_null for categorical (#8353)
• time.cast(str) as strftime (#8351)
• fix logical dtypes in parallel list collection (#8349)
• improve logical types of explode operation (#8348)
• logical type in anonymous list builders (#8346)
• escape csv header names if they contain special chars (#8331)
• nested struct/list/categorical logical/physical (#8334)
• fix deserialize empty list (#8326)
• fix coalesce schema (#8324)
• don't do null propagation (#8322)
• ensure invalid list eval raises (#8317)
• pass name to struct construction in aggregation (#8299)
• Use three slashes for doc comments (#8284)
• improve nested list construction (#8278)
• Fix DataFrame.sum returning empty column names (#8283)
• always sort in top_k fast path (#8275)
• don't use fast paths for sorted join if there are … (#8272)
• fix boolean par materialization (#8257)
• improve null/empty list construction (#8255)
• fix offsets in parallel utf8 materialization (#8254)
• nested struct logical type consistency (#8249)
• keep literal state if elementwise function is applied (#8195)
• decimal ensure backed arrow arrays have correct dtype (#8193)
• ensure cached nodes are initialized once (#8103)
• validate map lenghts (#8147)
• fix row-wise init of UInt64 values that exceed Int64 upper bound (#8146)
• implement list<null> constructor (#8143)
• add all primitives to av_buffer builder (#8140)
• struct is_in (#8139)
• fix wrong display name of binary expressions (#8131)
• lazy: fix boolean sum...

Python Polars 0.17.12

🚀 Performance improvements

• add fused multiply add optimization for expressions (#8690)
• use expression for dot product (#8686)

✨ Enhancements

• streaming unions (#8676)
• allow arr.to_struct to take a list of field names, fix it for Series, improve related docstrings (#8673)
• expression cache (#8674)
• rolling covariance and correlation (#8671)
• .to_physical() for List(Categorical) (#8499)
• allow from_repr to handle parsing of table reprs with no dtype row (#8640)
• Add dt.to_string alias for dt.strftime (#8290)
• support DataFrame export to numpy structured/record arrays (#8628)
• support transparent DataFrame init from numpy structured/record arrays. (#8620)
• Prettify show_versions (#8627)

🐞 Bug fixes

• allow arr.to_struct to take a list of field names, fix it for Series, improve related docstrings (#8673)
• block predicate containing shifts and windows after sort (#8670)
• ensure perfect hash table processes the nulls (#8668)
• Reading more tiny CSVs than workers in parallel will deadlock (#8441)
• respect maintain_order in partitioned groupby (#8653)
• fix explode null series (#8654)
• fix categorical agg type (#8645)
• allow list<null> -> list<cat> (#8636)

🛠️ Other improvements

• add notes/examples on use of inline regex flags to replace docstrings (#8685)
• Add "See Also" sections for alias, map_alias, prefix, s… (#8682)
• add notes/examples on use of inline regex flags to extract_all docstrings (#8675)
• allow arr.to_struct to take a list of field names, fix it for Series, improve related docstrings (#8673)
• add notes on the use of inline regex flags to extract docstrings (#8669)
• Add missing implode to internal functions (#8667)
• Clean up type checking imports (#8666)
• Organize PySeries impl blocks (#8665)
• clean-up some examples, extend pipe docstring (#8658)
• add notes on the use of inline regex flags to contains docstrings (#8657)
• fix/improve from_repr example/doctest (#8642)
• Improve some bindings imports (#8630)
• Move functions in Rust bindings to functions module (#8629)
• only require typing_extensions before Python 3.8 (#8623)
• Set up separate modules for lazy classes (#8624)
• Remove duplicate util in Rust bindings (#8622)
• Move Python version to env in release workflow (#8621)

Thank you to all our contributors for making this release possible!
@MarcoGorelli, @alexander-beedie, @dependabot, @dependabot[bot], @ghuls, @jonashaag, @josh, @mcrumiller, @ritchie46 and @stinodego