Rust Polars 0.52.0

🏆 Highlights

• Add LazyFrame.{sink,collect}_batches (#23980)
• Deterministic import order for Python Polars package variants (#24531)

🚀 Performance improvements

• Lazy gather for {forward,backward}_fill in group-by contexts (#25115)
• Don't recompute full rolling moment window when NaNs/nulls leave the window (#25078)
• Skip filtering scan IR if no paths were filtered (#25037)
• Optimize ipc stream read performance (#24671)
• Bump foldhash to 0.2.0 and hashbrown to 0.16.0 (#25014)
• Lower unique to native group-by and speed up n_unique in group-by context (#24976)
• Better parallelize take{_slice,}_unchecked (#24980)
• Implement native skew and kurtosis in group-by context (#24961)
• Use native group-by aggregations for bitwise_* operations (#24935)
• Address group_by_dynamic slowness in sparse data (#24916)
• Native filter/drop_nulls/drop_nans in group-by context (#24897)
• Implement cumulative_eval using the group-by engine (#24889)
• Prevent generation of copies of Dataframes in DslPlan serialization (#24852)
• Implement native null_count, any and all group-by aggregations (#24859)
• Speed up reverse in group-by context (#24855)
• Prune unused categorical values when exporting to arrow/parquet/IPC/pickle (#24829)
• Don't check duplicates on streaming simple projection in release mode (#24830)
• Lower approx_n_unique to the streaming engine (#24821)
• Duration/interval string parsing optimisation (2-5x faster) (#24771)
• Use native reducer for first/last on Decimals, Categoricals and Enums (#24786)
• Implement indexed method for BitMapIter::nth (#24766)
• Pushdown slices on plans within unions (#24735)
• Optimize gather_every(n=1) to slice (#24704)
• Lower null count to streaming engine (#24703)
• Native streaming gather_every (#24700)
• Pushdown filter with strptime if input is literal (#24694)
• Avoid copying expanded paths (#24669)
• Relax filter expr ordering (#24662)
• Remove unnecessary groups call in aggregated (#24651)
• Skip files in scan_iceberg with filter based on metadata statistics (#24547)
• Push row_index predicate for all scan types (#24537)
• Perform integer in-filtering for Parquet inequality predicates (#24525)
• Stop caching Parquet metadata after 8 files (#24513)

✨ Enhancements

• Improve error message on unsupported SQL subquery comparisons (#25135)
• Rewrite IR::Scan to IR::DataFrameScan in expand_datasets when applicable (#25106)
• Support ewm_var/std in streaming engine (#25109)
• Make DSL-hash skippable (#25140)
• Streaming {Expr,LazyFrame}.rolling (#25058)
• Set polars/<version> user-agent (#25112)
• Add BIT_NOT support to the SQL interface (#25094)
• Support BYTE_ARRAY backed Decimals in Parquet (#25076)
• Add allow_empty flag to item (#25048)
• Support ewm_mean() in streaming engine (#25003)
• Improve row-count estimates (#24996)
• Remove filtered scan paths in IR when possible (#24974)
• Introduce remote Polars MCP server (#24977)
• Allow local scans on polars cloud (configurable) (#24962)
• Add Expr.item to strictly extract a single value from an expression (#24888)
• Add environment variable to roundtrip empty struct in Parquet (#24914)
• Add glob parameter to scan_ipc (#24898)
• Prevent generation of copies of Dataframes in DslPlan serialization (#24852)
• Add list.agg and arr.agg (#24790)
• Implement {Expr,Series}.rolling_rank() (#24776)
• Support MergeSorted in CSPE (#24805)
• Duration/interval string parsing optimisation (2-5x faster) (#24771)
• Recursively apply CSPE (#24798)
• Add streaming engine per-node metrics (#24788)
• Add arr.eval (#24472)
• Improve rolling_(sum|mean) accuracy (#24743)
• Add nth_set_bit_u64() with unit test (#24035)
• Add separator to {Data,Lazy}Frame.unnest (#24716)
• Add union() function for unordered concatenation (#24298)
• Add name.replace to the set of column rename options (#17942)
• Allow duration strings with leading "+" (#24737)
• Drop now-unnecessary post-init "schema_overrides" cast on DataFrame load from list of dicts (#24739)
• Add support for UInt128 to pyo3-polars (#24731)
• Implement maintain_order for cross join (#24665)
• Add support to output dt.total_{}() duration values as fractionals (#24598)
• Support scanning from file:/path URIs (#24603)
• Log which file the schema was sourced from, and which file caused an extra column error (#24621)
• Add LazyFrame.{sink,collect}_batches (#23980)
• Deterministic import order for Python Polars package variants (#24531)
• Add support to display lazy query plan in marimo notebooks without needing to install matplotlib or mermaid (#24540)
• Add unstable hidden_file_prefix parameter to scan_parquet (#24507)
• Use fixed-scale Decimals (#24542)
• Add support for unsigned 128-bit integers (#24346)

🐞 Bug fixes

• Fix CSV select(len()) off by 1 with comment prefix (#25069)
• Fix incorrect reshape on sliced lists (#25139)
• Support "index" as column name in group_by iterator (#25138)
• DSL_SCHEMA_HASH should not changed by line endings (#25123)
• Solve multiple issues relating to arena mutation in SQL subqueries (#25110)
• Fix panic in dt.truncate for invalid duration strings (#25124)
• Don't trigger DeprecationWarning from SQL "IN" constraints that use subqueries (#25111)
• Return the correct string-case Expr reprs (#25101)
• Fix groups update on slices with different offsets (#25097)
• Fix handling Null dtype in ApplyExpr on group_by (#25077)
• Raise error for all/any on list instead of panic (#25018)
• Unique key names in streaming sort/top_k (#25082)
• The SQL interface should use logical, not bitwise, behaviour for unary "NOT" operator (#25091)
• Fix panic if scan predicate produces 0 length mask (#25089)
• Ensure SQL table alias resolution checks against CTE aliases on fallback (#25071)
• Panic in group_by_dynamic with group_by and multiple chunks (#25075)
• Fix panic when using struct field as join key (#25059)
• Allow broadcast in group_by for ApplyExpr and BinaryExpr (#25053)
• Fix field metadata for nested categorical PyCapsule export (#25052)
• Block predicate pushdown when group_by key values are changed (#25032)
• Group-By aggregation problems caused by AmortSeries (#25043)
• Don't push down predicates passed inserted cache nodes (#25042)
• Allow for negative time in group_by_dynamic iterator (#25041)
• Re-enable CPU feature check before import (#25010)
• Correctness any(ignore_nulls) and OOB in all (#25005)
• Streaming any/all with ignore_nulls=False (#25008)
• Fix incorrect join_asof on a casted expression (#25006)
• Optimize memory on rolling groups in ApplyExpr (#24709)
• Fallback Pyarrow scan to in-memory engine (#24991)
• Make Operator::swap_operands return correct operators for Plus, Minus, Multiply and Divide (#24997)
• Capitalize letters after numbers in to_titlecase (#24993)
• Preserve null values in pct_change (#24952)
• Raise length mismatch on over with sliced groups (#24887)
• Check duplicate name in transpose (#24956)
• Follow Kleene logic in any / all for group-by (#24940)
• Do not optimize cross join to iejoin if order maintaining (#24950)
• Broadcast partition_by columns in over expression (#24874)
• Clear index cache on stacked df.filter expressions (#24870)
• Fix 'explode' mapping strategy on scalar value (#24861)
• Fix repeated with_row_index() after scan() silently ignored (#24866)
• Correctly return min and max for enums in groupby aggregation (#24808)
• Refactor BinaryExpr in group_by dispatch logic (#24548)
• Fix aggstate for gather (#24857)
• Keep scalars for length preserving functions in group_by (#24819)
• Have range feature depend on dtype-array feature (#24853)
• Fix duplicate select panic (#24836)
• Inconsistency of list.sum() result type with None values (#24476)
• Division by zero in Expr.dt.truncate (#24832)
• Potential deadlock in __arrow_c_stream__ (#24831)
• Allow double aggregations in group-by contexts (#24823)
• Series.shrink_dtype for i128/u128 (#24833)
• Fix dtype in EvalExpr (#24650)
• Allow aggregations on AggState::LiteralScalar (#24820)
• Dispatch to group_aware for fallible expressions with masked out elements (#24815)
• Fix error for arr.sum() on small integer Array dtypes containing nulls (#24478)
• Fix XOR did not follow kleene when one side is unit-length (#24810)
• Incorrect precision in Series.str.to_decimal (#24804)
• Use overlapping instead of rolling (#24787)
• Fix iterable on dynamic_group_by and rolling object (#24740)
• Use Kahan summation for in-memory groupby sum/mean (#24774)
• Release GIL in PythonScan predicate evaluation (#24779)
• Type error in bitmask::nth_set_bit_u64 (#24775)
• Add Expr.sign for Decimal datatype (#24717)
• Correct str.replace with missing pattern (#24768)
• Support decimal_comma on Decimal type in write_csv (#24718)
• Parse Decimal with comma as decimal separator in CSV (#24685)
• Make Categories pickleable (#24691)
• Shift on array within list (#24678)
• Fix handling of AggregatedScalar in ApplyExpr single input (#24634)
• Support reading of mixed compressed/uncompressed IPC buffers (#24674)
• Overflow in slice-slice optimization (#24658)
• Package discovery for setuptools (#24656)
• Add type assertion to prevent out-of-bounds in GenericFirstLastGroupedReduction (#24590)
• Remove inclusion of polars dir in runtime sdist/wheel (#24654)
• Method dt.month_end was unnecessarily raising when the month-start timestamp was ambiguous (#24647)
• Fix unsupported arrow type Dictionary error in scan_iceberg() (#24573)
• Raise Exception instead of panic when unnest on non-struct column (#24471)
• Include missing feature dependency from polars-stream/diff to polars-plan/abs (#24613)
• Newline escaping in streaming show_graph (#24612)
• Do not allow inferring (-1) the dimension on any Expr.reshape dimension except the first (#24591)
• Sink batches early stop on in-memory engine (#24585)
• More precisely model expression ordering requirements (#24437)
• Panic in zero-weight rolling mean/var (#24596)
• Decimal <-> literal arithmetic supertype rules (#24594)
• Match various aggregation return types in the streaming engine with the in-memory engine (#24501)
• Validate list type for list expressions in planner (#24589)
• Have log() prioritize the leftmost dtype for its output dtype (#24581)
• CSV pl.len() was incorrect (#24587)
• Add support for float inputs for duration types (#24529)
• Roundtrip empty string through hive partitioning (#24546)
• Fix potential OOB writes in unaligned IPC read (#24550)
• Fix regression error when scanning AWS presigned URL (#24530)
• Make PlPath::join for cloud paths replace on absolute paths (#24514)
• Correct dtype for cum_agg in streaming engine (#24510)
• Escape backslashes in EscapeLabel to produce valid DOT labels (#24532)

📖 Documentation

• Mention Narwhals in ecosystem page (#25100)
• Fix typo in public dataset URL (#25044)
• Introduce remote Polars MCP server (#24977)
• Update Cloud docs with correct fn argument order (#24939)
• Add i128 and u128 features to user guide (#24938)
• Relax fsspec wording (#24881)
• Fix duplicated article in SECURITY.md (#24762)
• Specify that precision=None becomes 38 for Decimal (#24742)
• Mention polars[rt64] and polars[rtcompat] instead of u64-idx and lts-cpu (#24749)
• Fix source mapping (#24736)
• Fix syntax error in data-types-and-structures.md (#24606)

📦 Build system

• Make building the docs on macOS more reliable (#25095)
• Ensure build_feature_flags.py is included in artifact (#25024)
• Python pre-release 1.34.0b5 (#24699)
• Use cargo-run to call dsl-schema script (#24607)

🛠️ Other improvements

• Support for named/anonymous aggregations (#25118)
• Silence unused mut warning (#25093)
• Remove old join projection pushdown logic (#25088)
• Disable recursive CSPE for now (#25085)
• Remove unused row-count (#25080)
• Add proptest strategies for Series logical types (#24849)
• Add stateful EwmCov kernel (#25065)
• Add IR for scan_lines (#25066)
• Change group length mismatch error to ShapeError (#25004)
• Move asof tolerance type coercion to IR conversion (#25033)
• Move EwmMeanState to polars-compute (#25034)
• Update toolchain (#25007)
• Fix benchmark ci (#25019)
• Fix non-deterministic test (#25009)
• Fix makefile arch detection (#25011)
• Make LazyFrame.set_sorted into a FunctionIR::Hint (#24981)
• Update row estimation and reader schema in filter_scan_ir (#24995)
• Insert casts for ewm_mean inputs in type coercion (#24992)
• Remove unused expr_eval (#24988)
• Remove symbolic links (#24982)
• Add stateful EwmMean kernel (#24972)
• Dispatch to no-op rayon thread-pool from streaming (#24957)
• Add function to filter IR::Scan based on indices (#24979)
• Organize code for opaque functions in a module (#24978)
• Move scan filter code to polars-mem-engine (#24959)
• Unpin pydantic (#24955)
• Ensure safety of scan fast-count IR lowering in streaming (#24953)
• Expose polars_compute from polars (#24556)
• Re-use iterators in set_ operations (#24850)
• Move order code to instance function (#24895)
• Visualization data generator for streaming physical plan (#24896)
• Remove GroupByPartitioned and dispatch to streaming engine (#24903)
• Improve IR visualization for IEJoin (#24902)
• Turn element() into {A,}Expr::Element (#24885)
• Pass ScanOptions to new_from_ipc (#24893)
• Update tests to be index type agnostic (#24891)
• Remove legacy order_sensitive code (#24894)
• Rename text_plan_graph to visualization_data (#24878)
• Use UnifiedScanArgs in new_from_ipc and remove LazyIpcReader (#24883)
• Document safety of CategoricalToArrowConverter (#24876)
• Unset Context in Window expression (#24875)
• Unify expression order resolution (#24723)
• Move FunctionExpr dispatch from plan to expr (#24839)
• Fix SQL test giving wrong error message (#24835)
• Consolidate dtype paths in ApplyExpr (#24825)
• Add days_in_month to documentation (#24822)
• Enable ruff D417 lint (#24814)
• Turn pl.format into proper elementwise expression (#24811)
• Fix remote benchmark by no-longer saving builds (#24812)
• Expose function on IPC writer to write dictionary batches (#24802)
• Refactor ApplyExpr in group_by context on multiple inputs (#24520)
• IR text plan graph generator (#24733)
• Move Series to_arrow() logic to struct function (#24794)
• Temporarily pin pydantic to fix CI (#24797)
• Extend and rename rolling groups to overlapping (#24577)
• Refactor DataType proptest strategies (#24763)
• Add union to documentation (#24769)
• Cleaner whitespace skipping in CSV field parser (#24705)
• Remove duplicate maintain_order from CrossJoinOptions (#24725)
• Change function order flags to be less error prone (#24604)
• Remove {Upper,Lower}Bound expressions in IR (#24701)
• Fix Makefile uv pip option syntax (#24711)
• Add egg-info to gitignore (#24712)
• Restructure python project directories again (#24676)
• Use IR for polars-expr output field resolution (#24661)
• Add proptest strategies for Series physical types (#24549)
• Expose CloudScheme via polars::prelude (#24643)
• Remove dist/ from release python workflow (#24639)
• Escape sed ampersand in release script (#24631)
• Remove PyOdide from release for now (#24630)
• Fix sed in-place in release script (#24628)
• Release script pyodide wheel (#24627)
• Release script pyodide wheel (#24626)
• Update release script for runtimes (#24610)
• Remove tokio-util dependency (#24617)
• Remove unused UnknownKind::Ufunc (#24614)
• Use cargo-run to call dsl-schema script (#24607)
• Genericize UnitVec for any T (#24597)
• Cleanup and prepare to_field for element and struct field context (#24592)
• Resolve nightly clippy hints (#24593)
• Rename pl.dependencies to pl._dependencies (#24595)
• More release scripting (#24582)
• Again a minor fix for the setup script (#24580)
• Minor fix in release script (#24579)
• Correct release python beta version check (#24578)
• Python dependency failure (#24576)
• Always install yq (#24570)
• Deterministic import order for Python Polars package variants (#24531)
• Check Arrow FFI pointers with an assert (#24564)
• Add CloudScheme::FileNoHostname variant (#24535)
• Add a couple of missing type definitions in python (#24561)
• Fix quickstart example in Polars Cloud user guide (#24554)
• Add implementations for loading min/max statistics for Iceberg (#24496)
• Move collapse_joins optimizer logic into predicate pushdown optimizer (#24495)

Thank you to all our contributors for making this release possible!
@DeflateAwning, @EndPositive, @EnricoMi, @FBruzzesi, @JakubValtar, @Kevin-Patyk, @Liyixin95, @MarcoGorelli, @Object905, @alexander-beedie, @alonsosilvaallende, @andreseje, @borchero, @carnarez, @cmdlineluser, @coastalwhite, @craigalodon, @dangotbanned, @deanm0000, @dsprenkels, @eitsupi, @etrotta, @henryharbeck, @itamarst, @jan-krueger, @jordanosborn, @kdn36, @lzcmian, @math-hiyoko, @mcrumiller, @mjanssen, @moizescbf, @nameexhaustion, @orlp, @pavelzw, @r-brink, @ritchie46, @stijnherfst, @thomasjpfan and @williambdean