🛠️ Other improvements

• Backport 1.44.2 (#29216)

Thank you to all our contributors for making this release possible!
@EndPositive, @dsprenkels, @kdn36, @lun3x, @nameexhaustion and @orlp

💥 Breaking changes

• Set the default engine for SQL to the streaming engine (#28973)

🚀 Performance improvements

• Reuse native metadata for Iceberg sinks (#29062)
• SQL exists predicate pushdown before subqueries (#29078)
• Collect primitive group-by aggregations into single chunk (#28825)
• Use cost information to determine whether to keep cached nodes (#29042)
• Use scan cardinality in build side if sampling is exhausted (#29040)

✨ Enhancements

• Defer SQL resolving until we convert to IR (#29077)
• Expose Iceberg sink writer options (#29065)
• Support partitioned Iceberg sinks (#28823)
• Expose fixed-array inner product in SQL (#29033)
• Add strip_prefix and strip_suffix to expression names (#29041)
• Use scan information in join reordering (#29038)
• Add cardinality information (#29024)
• Allow customizing explain output for debugging custom io sources (#23978)
• Add more expression properties to meta namespace (#28091)
• Improve SQL coverage (#29010)
• Improve SQL coverage (#29006)
• Add Join reordering. (#28985)
• Merge 2.0 into main (#28982)
• Set the default engine for SQL to the streaming engine (#28973)

🐞 Bug fixes

• Don't keep incrementing morsel id in MergeSortedNode pass-through (#29055)
• Ensure show_graph shows physical plan for auto engine (#29011)
• Assign SQL JOIN literal comparisons to the correct input (#28701)
• Make distributor linearizer capacity consistent (#29057)
• Correct peak visitors, dictionary bounds, and Date feature gating (#29031)
• Keep extension type schema consistent (#29039)
• Fix Series.sample order when with_replacement=True and shuffle=False (#28990)
• Reduce memory in multi_scan pipeline PostApplyExtraOps (#29049)
• Fix SO in rayon caused by join_where (#29051)
• Clarify GPU installation guidance (#29037)
• Remove POLARS_AUTO_STRUCTIFY env var backdoor (#29032)
• Ensure metrics are flushed between phases and before logging (#29014)
• SQL parse a typed DATE literal instead of casting it (#29007)
• Fix parquet decode of plain pages in dictionary column (#29001)
• Reserve fixed-size-list child capacity (#28980)
• Fix SQL casts (#28986)
• Fix incorrect condition in combine_validities_and_many and add test (#28909)
• Give sink_batches lazy: Literal[False] overload a default (#28951)

📖 Documentation

• Update 2.0.0-rc1 migration guide with latest changes (#28983)
• Fix invalid output in DataFrame.sample example (#28998)

🛠️ Other improvements

• Bump rust toolchain (#29080)
• Increase rustc stack size (#29076)
• Log pytest worker crashes and disable restarting (#29058)
• Replace FileInfo row_estimation tuple with typed ScanStats (#29023)
• Use an if for cfg(debug_assertions) to fix the benchmark job (#29002)
• Remove 2.0 branch from ci-tested branches (#28981)
• Skip tests that are currently failing on windows (#28962)

Thank you to all our contributors for making this release possible!
@0guban0v, @0xC61, @Aniket-a14, @LarryHu0217, @MatteoPossamai, @NeejWeej, @TNieuwdorp, @WaterWhisperer, @adamreeve, @dsprenkels, @jonasdedden, @kdn36, @math-hiyoko, @matthewbayer, @nameexhaustion, @orlp, @ritchie46, @severinh and @sivakumar-mahalingam

Thank you to all our contributors for making this release possible!
@Kevin-Patyk, @henrytsanford, @jonasdedden, @orlp and @ritchie46

⚠️ Deprecations

• Deprecate rechunk parameter for all read/scan functions (#28063)
• Deprecate Expr.rechunk() (#28692)
• Deprecate struct.rename_fields() with an incorrect number of fields (#28672)

🚀 Performance improvements

• Add private env var toggle for HTTP rate limit (#28882)
• Relax default CloudRetryConfig for rate limit stability (#28885)
• Elide generic cross join on subquery decorrelation in equality predicates (#28876)
• cache CTE's in SQL layer (#28864)
• Allow CSPE if manual caches are set (#28859)
• Lower unqualified join predicates to inner joins in SQL (#28854)
• Rechunk mask for DataFrame filter (#28762)
• Improve performance of when/then/otherwise by masking out unevaluated elements (#28498)
• Drop unused projections in filter on streaming engine (#28713)
• Retain Parquet Partial metadata on filter (#28737)

✨ Enhancements

• Support integer fixed-array dot products (#28829)
• SQL correlated in (#28927)
• Support more join_types in join_where (#28880)
• Support Iceberg schema evolution (#28794)
• SQL conformance (#28494)
• Introduce RemoteEngine and a common base class for all engines (#28800)
• Support Iceberg table with V3 deletion vectors in native scan_iceberg (#28772)
• Support Iceberg snapshot properties (#28793)
• Expose sinked_paths_callback on sink_parquet as unstable parameter (#28814)
• Add infer_schema_files to CSV inference hint (#28809)
• Add native fixed-array dot (#28504)
• Export query metrics to polars_cloud (#28757)
• Support Iceberg object storage paths (#28634)
• More CSEE simplification (#28731)
• Improve error in Series constructor with name in context (#28743)
• Add adaptive HTTP rate-limiter for cloud IO (#28591)
• Add struct.drop() (#28666)
• Improve error message when CSV name de-duplication fails (#28658)
• Always keep first metadata per source for Parquet (#28661)
• Improve plan-time row estimates for multi-file parquet scans (#28380)
• Expose array and plugin function views in Python visitor (#28635)

🐞 Bug fixes

• SQL handle quantified comparisons against a subquery (#28929)
• Fix SQL subquery qualified lowering and cache row-index (#28926)
• Clippy-stable failures (#28919)
• Use uuidv7 for cloud observed queries (#28910)
• Unsoundness in AnyValue::into_static for structs (#28889)
• Invalidate suborders on projection (#28866)
• Ensure SQL function registry is available in isolated subqueries (#28881)
• Handle null in Expr.is_not_nan (#28883)
• Ensure eager unpivot column selection aligns with the lazy engine (#28846)
• Fix assertion error / incorrect data load from parquet written by fastparquet (#28656)
• Fix projection pushdown incorrect select() height (#28751)
• Restore monitoring as an engine-level parameter (#28821)
• Bincode serialization of IR hints (#28837)
• Retain datetime inference across CSV fallback (#28663)
• Avoid chunk fragmentation on bool agg min and max (#28789)
• Merge join with coalesce and empty suffix (#28799)
• Wrong function name call in test (#28801)
• Preserve row mapping in nested over expressions (#28767)
• Restore CI compatibility with NumPy 2.5.2 (#28782)
• Do not deduplicate inherently nondeterministic plan nodes (#28768)
• Fix OOC spilling of categoricals (#28761)
• Correct partitionable filter handling for pivot (#28749)
• Small typo in docstring (#28763)
• Avoid chunk fragmentation on bool agg any and all (#28754)
• Ignore nans in (min|max)_horizontal (#28710)
• Correct function display for str.replace_all (#28742)
• Exclude debug tests from nodebug streaming run (#28747)
• Convert predicate series dtype during prefiltered parquet reading (#28711)
• Do not remove nested caches when performing predicate pushdown past a cache node (#28740)
• Correct handling of nulls at the start of business day functions (#28703)
• Do not panic when exceeding Parquet metadata scan cache (#28721)
• Remove cryptographic hashing from CSPE (#28716)
• Unsoundness in rayon block_on (#28709)
• Check for (shallow) IR node equality on top of hashing in CSPE (#28506)
• Don't hand IO plugins a predicate they cannot evaluate (#28643)
• Raise on overflow in Decimal sum instead of silently wrapping (#28688)
• Preserve nulls when importing Arrow maps (#28680)
• Propagate null by column values in rolling_*_by (#27367)
• Fix self-referencing field in struct.with_fields with over (#28678)
• Fix Arrow buffer offset for Utf8 and Binary (#28662)
• Clamp group-by slice offset (#28579)
• Release the GIL while resolving the schema in __arrow_c_stream__ (#28642)
• Fix data corruption on Series from nested Arrow LargeList (#28632)

📖 Documentation

• Interlink join docstrings (#28907)
• Migration guide for 2.0 release (#28788)
• Clarify read_database_uri requirements for SQLAlchemy (#28366)
• Update engine tags (#28852)
• Clarify "that that side" comment in asof_join (#28847)
• Update mage.ai documentation link (#28813)
• Add engine tags (#28708)
• Document that arg_extremum functions return any index on ties (#28691)
• Fix Polars Cloud API reference link (#28693)

🛠️ Other improvements

• Bump runtime toolchains (#28924)
• Add min-publish-age for cargo (#28906)
• Tighten join invariants DSL (#28913)
• Bump Rust toolchain (#28900)
• Ensure that predicates are pushed down to the scans (#28857)
• Clarify "that that side" comment in asof_join (#28847)
• Restore monitoring as an engine-level parameter (#28821)
• Remove workaround for inconsistent CSE (#28834)
• Introduce RemoteEngine and a common base class for all engines (#28800)
• Add row count and file byte size to sinked paths callback (#28522)
• Use canonical expression IDs in CSEE (#28786)
• Enforce 100% type coverage in CI with Pyrefly (#28795)
• Attribute annotations for CredentialProviderAWS and CredentialProviderAzure (#28790)
• Attribute annotations for ScanCastOptions (#27906)
• Disable credentials in upload chunk size tests (#28745)
• Improve backtrace path formatting (#28732)
• Exclude debug tests from nodebug streaming run (#28747)
• Mark test_grouped_agg_parametric as slow (and add param ids) (#28715)
• Fix first expect in test_group_by_arg_max_boolean_26978 (#28690)
• Fix the name of struct.drop() in rename_fields() deprecation message (#28687)
• Add dist=loadgroup to the pytest config (#28676)
• Enable a lot of may_fail_auto_streaming tests (#28675)
• Re-enable test_extension() for streaming engine (#28611)
• Update test_hive_join_rewrite_semi_join test to work with streaming engine (#28610)

Thank you to all our contributors for making this release possible!
@0guban0v, @JakubValtar, @Joosboy, @Kevin-Patyk, @MatteoPossamai, @NicoOhR, @TNieuwdorp, @VedantMadane, @aarushkandukoori, @alexander-beedie, @azimafroozeh, @borchero, @carnarez, @dancsi, @dependabot[bot], @dsprenkels, @gautamvarmadatla, @jonasdedden, @jorenham, @kdn36, @lzcmian, @malhotrashivam, @matthewbayer, @mikhail5555, @nameexhaustion, @orlp, @ritchie46, @subotac and dependabot[bot]

✨ Enhancements

• Add adaptive HTTP rate-limiter for cloud IO (#28591)

🐞 Bug fixes

• Unsoundness in rayon block_on (#28709)
• Check for (shallow) IR node equality on top of hashing in CSPE (#28506)

📖 Documentation

• Document that arg_extremum functions return any index on ties (#28691)

Thank you to all our contributors for making this release possible!
@dancsi, @dsprenkels, @kdn36, @orlp and @ritchie46

This Releases' DSL matches Python 1.43.2.

🚀 Performance improvements

• Pushdown len() to concat/union inputs (#28570)
• Optimize not(bool_f) to not_bool_f (#28474)
• Split multiplexers that directly scan from in-memory DataFrame (#28376)
• Make DNS cache global (#28352)
• Do not remove cache if predicates not pushed to all inputs (#28341)
• Environment variable for logging slow DNS lookup (#28211)
• Pre-partition on left, right and semi joins on hive partitioned data (#28374)
• Rewrite inner joins on hive partitioned data to a union of partitions filtered joins (#28327)
• Tighten redundant comparisons and propagate filter constraints (#27999)
• Canonicalize predicates (#28212)
• Remove excess memory copy in streaming IPC sink (#28141)
• Parallelize scan_iceberg resolve (#28168)
• Chunk-aware morsel splitting on single-file IO sink (#27950)
• Don't allocate for full_null() with small lengths (#28181)
• Use monotonic deque for rolling min_by/max_by (O(n)) (#27436)
• Add a sampled resolve mode for multi-file parquet metadata (#28111)
• Speed up small dtype series sums with a upcast sum kernel (#27958)
• Don't block on path expansion (#28073)
• Add bytes-based concurrency control for cloud IO (#27924)
• Stop flushing multiplexer on phase change (#28013)
• Prevent empty chunks from triggering copy in rechunk (#27953)
• Improve performance of struct unnest inside list eval on streaming (#27905)

✨ Enhancements

• Add struct.drop() (#28666)
• Improve error message when CSV name de-duplication fails (#28658)
• Always keep first metadata per source for Parquet (#28661)
• Improve plan-time row estimates for multi-file parquet scans (#28380)
• Serialize and deserialize SinkTypeIR::Partitioned (#28112)
• Add infer_schema_files parameter to scan_csv (#28440)
• Support reading IEEE 754 total order Parquet column order (#27896)
• Expose more Expr nodes for cudf_polars (pt 2) (#28404)
• Allow callback sinks on cloud (#28458)
• Pre-partition group-by on hive keys (#28444)
• Add ewm_sum and ewm_sum_by #28151 (#28215)
• Serve stale records from object_store DNS cache (#28256)
• Expose more expr nodes for cudf-polars (#28117)
• Make partition_hive an opt flag (#28345)
• When displaying IRExprs, only add parentheses when needed for disambiguation (#28319)
• Show only differing dtypes in assert_frame_equal error (#27816)
• Add Clone to SpillFrame/Token (#28302)
• Add Series.degrees/radians and clarify trig functions use radians (#22961)
• Merge sorted with multikey (#28067)
• Add list expression which consistently packs elements together into new List type (#27990)
• Construct pyarrow predicates via PyO3 instead of eval str (#27271)
• Optimize joins with redundant equi-join keys (#28017)
• Implement missing datetime options for CastColumnsPolicy (#28084)
• Add Expr.cat.to and Expr.cat.physical (#28096)
• Add POLARS_OOC_DISK_BUDGET_MB (#28045)
• Close ResourceWarning leaks in database tests (#28066)
• Expose IRFunctionExpr::Fused in the python node visitor (#27889)
• Deprecate casts from string to temporal dtypes (#28056)
• Add naive out-of-core spilling to Polars (#27998)
• Add experimental strict mode (#28023)
• Optimize non-negative len and null_count comparisons (#28002)
• Optimize len and null_count comparisons (#27727)
• Support SQL's implicit JOIN syntax (#27890)
• Sample from bivariate distribution for spill context Thompson sampling (#27973)
• Add Expr.is_sorted (#26708)
• Add suggestions in wrong api usage or mismatched column names (#27954)
• Add external object_store support for non-native schemes (#27871)
• Skip Delta files and parquet row groups using per-field struct statistics (#27887)
• Add re-registration of OOC SpillTokens (#27909)
• Improve IR sortedness detection for with_row_index and explode (#27875)
• Add DataFrame.is_sorted() (#27870)

🐞 Bug fixes

• Don't hand IO plugins a predicate they cannot evaluate (#28643)
• Don't hang or crash on sqrt/cbrt/pct_change/ewm_* with a Struct column (#28696)
• Raise on overflow in Decimal sum instead of silently wrapping (#28688)
• Preserve nulls when importing Arrow maps (#28680)
• Propagate null by column values in rolling_*_by (#27367)
• Fix self-referencing field in struct.with_fields with over (#28678)
• Fix Arrow buffer offset for Utf8 and Binary (#28662)
• Clamp group-by slice offset (#28579)
• Ensure categorical fill_null(strategy="min"/"max") uses lexical min/max (#28636)
• Release the GIL while resolving the schema in __arrow_c_stream__ (#28642)
• Fix data corruption on Series from nested Arrow LargeList (#28632)
• Properly propagate enum metadata for iceberg column mapping (#28580)
• Correctly write parquet field IDs for enums and categoricals (#28581)
• Fix arrow C interop binview offset (#28623)
• Fix duplicate hive values in hive pre-partition rewrite (#28621)
• Double-counted offset for Arrow export of sliced Series(Array) (#28602)
• Struct/List/Array equality handling in sort and join (#28601)
• Use try_new in StructArray construction in polars-json (#27489)
• Raise ComputeError instead of panicking in repeat_by when output exceeds IdxSize::MAX (#27892)
• Run type coercion pass on pivot's internally generated group_by (#27897)
• More careful slice pushdown into joins (#28578)
• Preserve ordering in sliced unions (#28576)
• Drop input sortedness when casting to a string (#28574)
• Clear sortedness flags in StringChunked substring kernels (#28573)
• Bad mask handling when reading optional parquet column (#28547)
• Any operation on Unknown(Int) and Unknown(Float) should result in Unknown(Float) (#28545)
• Flip nulls_last after Expr.reverse() (#28572)
• Fix high blocking thread use in sink_parquet with async local path (#28543)
• Serialize LazyFrames backed by bytes (#28568)
• Release GIL in SQLContext.execute() (#28549)
• Propagate nulls_last in function_expr_sortedness (#28544)
• Incorrect slicing when a join requires sorting (#28541)
• Fix panic on self join of scan_delta / scan_iceberg (#28468)
• Decrement ParkGroup worker count when worker exits (#28492)
• Add missing Send bounds in Connector (#28497)
• Fix UB on first/last_non_null with empty chunk (#28495)
• Do not CSE non-column height expr on streaming engine (#28480)
• Propagate adjusted sortedness through Gather (#28493)
• Deduplicate the expression equality checks (#28483)
• Address 3VL issue with SQL NOT IN interaction with NULL values and joins (#28484)
• Use total comparison in Expr literal values (#28482)
• Ensure SQL SUM and CORR aggregates return NULL for all-null inputs, add TOTAL (#28475)
• Share null_count_dtype helper between Delta and Iceberg, fixing SchemaError (#28479)
• Remove non-output columns from the equi-join and semi/anti-join operators (#28446)
• Fix dropped slice on multiple unions (#28477)
• Fix in-memory engine incorrect slice on maintain order join (#28478)
• Check join schema by position (#28455)
• Block predicate pushdown past overwritten window keys (#28429)
• Avoid panic when union slice skips all rows (#28420)
• Solve panic in dt.replace when there were multiple chunks (#28437)
• Propagate is_scalar from the input to the output of .sort() and .sort_by() (#28438)
• Insert missing coercions from Unknown(_) in list/array arithmetic (#28411)
• Resolve CSV column names overwrite in DSL->IR conversion (#28383)
• Avoid IEJoin rewrite for Categorical comparisons (#28427)
• Do not rewrite sort().reverse() to sort(descending=True) when maintain_order=True (#28403)
• Propagate bigidx to polars-plan from polars (#28396)
• Ensure BinaryView offset+len does not exceed i32::MAX where possible (#28048)
• Invalid offset in strptime (#28388)
• Incorrect schema type for decimal <-> primitive division (#28373)
• Panic in in-memory CSEE handling (#28371)
• Apply same type coercion to IsBetween as binary comparisons (#28300)
• Fix offset in arrow ffi export of sliced struct arrays (#28369)
• Fix cross filter not applied with sink and CSE (#28297)
• Fix panic on projection pushdown with caches (#28280)
• Fix write_json() null values in Array columns being written incorrectly as null (#28330)
• Fix EntityTooSmall on sink_ipc to S3 (#28255)
• Raise error instead of silent wrapping for select(len()) (#28355)
• Float16 groupby aggregates (#28361)
• Respect lexical ordering of Categorical in top_k/bottom_k (#28359)
• Support dtype-list schema overrides in scan_csv (#28226)
• Resolve unknown type in fused multiply add (#28321)
• Honor aws_checksum_algorithm when provided (#28328)
• Fix regression in sourcing HF_TOKEN (#28317)
• Raise on addition/subtraction between temporal and non-temporal Series (#28266)
• Rewrite with_columns on empty df to select during DSL -> IR (#28298)
• Fix sink deadlock regression (#28296)
• Avoid panic when consumer of vertical concat is done (#28272)
• Ensure predicate simplification is deterministically ordered (#28269)
• Don't attribute untimed execution to optimization in profile (#28273)
• Harden IPC mmap API (#28258)
• Classify S3 region request failures as IO errors (#28225)
• Incorrect inner dtype in ArrayChunked::from_aligned_values (#28249)
• Unsoundness in arg_sort_ascending (#28245)
• Add column length check to row encoding (#28248)
• Raise on implode of Object dtype instead of creating invalid List(Object) (#28246)
• Don't panic in qcut on degenerate float input (all-NaN, infinite, include_breaks) (#28220)
• Fix streaming Strptime feature flags (#28242)
• Return null not 0 for the first unbiased ewm_var/ewm_std value (#28235)
• Use after free in file cache (#28236)
• Incorrect length calculation in parallel hashmap (#28227)
• Avoid slice pushdown panic on shared cache inputs (#28157)
• Incorrect dtype for Unknown rig...

⚠️ Deprecations

• Deprecate casts from Categorical to integer dtypes (#28525)
• Deprecate not setting the plan_stage argument in show_graph() (#28391)

🚀 Performance improvements

• Pushdown len() to concat/union inputs (#28570)

✨ Enhancements

• Issue FutureWarning on using from_arrow of ArrowStreamExportable (#28442)
• Add infer_schema_files parameter to scan_csv (#28440)

🐞 Bug fixes

• Properly propagate enum metadata for iceberg column mapping (#28580)
• Correctly write parquet field IDs for enums and categoricals (#28581)
• Fix arrow C interop binview offset (#28623)
• Fix duplicate hive values in hive pre-partition rewrite (#28621)
• Double-counted offset for Arrow export of sliced Series(Array) (#28602)
• Struct/List/Array equality handling in sort and join (#28601)
• More careful slice pushdown into joins (#28578)
• Preserve ordering in sliced unions (#28576)
• Drop input sortedness when casting to a string (#28574)
• Clear sortedness flags in StringChunked substring kernels (#28573)
• Bad mask handling when reading optional parquet column (#28547)
• Any operation on Unknown(Int) and Unknown(Float) should result in Unknown(Float) (#28545)
• Flip nulls_last after Expr.reverse() (#28572)
• Fix high blocking thread use in sink_parquet with async local path (#28543)
• Serialize LazyFrames backed by bytes (#28568)
• Release GIL in SQLContext.execute() (#28549)
• Propagate nulls_last in function_expr_sortedness (#28544)
• Incorrect slicing when a join requires sorting (#28541)

🛠️ Other improvements

• Fix duckdb delta extension install collision (#28607)

Thank you to all our contributors for making this release possible!
@BitWeaverDev, @Matt711, @Samoilov2004, @borchero, @dancsi, @dsprenkels, @kdn36, @masumi-ryugo, @nameexhaustion and @ritchie46

🚀 Performance improvements

• Optimize not(bool_f) to not_bool_f (#28474)

✨ Enhancements

• Allow callback sinks on cloud (#28458)

🐞 Bug fixes

• Fix panic on self join of scan_delta / scan_iceberg (#28468)
• Fix UB on first/last_non_null with empty chunk (#28495)
• Do not CSE non-column height expr on streaming engine (#28480)
• Propagate adjusted sortedness through Gather (#28493)
• Deduplicate the expression equality checks (#28483)
• Address 3VL issue with SQL NOT IN interaction with NULL values and joins (#28484)
• Use total comparison in Expr literal values (#28482)
• Ensure SQL SUM and CORR aggregates return NULL for all-null inputs, add TOTAL (#28475)
• Share null_count_dtype helper between Delta and Iceberg, fixing SchemaError (#28479)
• Remove non-output columns from the equi-join and semi/anti-join operators (#28446)
• Fix dropped slice on multiple unions (#28477)
• Fix in-memory engine incorrect slice on maintain order join (#28478)
• Check join schema by position (#28455)
• Block predicate pushdown past overwritten window keys (#28429)

📖 Documentation

• Update and restructure README (#28490)
• Minor fixes to Spark migration guide (#27730)
• Relocate Polars Cloud & On-Prem User Guide (#28462)
• Add notes on k8s operator (#28445)

🛠️ Other improvements

• Make hive_part extraction a function and public (#28507)
• Deduplicate the expression equality checks (#28483)
• Bump ruff and mypy package versions (#28456)
• Fix flaky test (#28454)

Thank you to all our contributors for making this release possible!
@AnirudhRahul, @EndPositive, @Jesse-Bakker, @alexander-beedie, @carnarez, @dancsi, @mdroogh, @mroeschke, @nameexhaustion, @nchammas, @orlp, @r-brink and @ritchie46

⚠️ Deprecations

• Deprecate casting numeric types to categoricals (#28349)
• Deprecate cat.get_categories() and cat.to_local() (#28299)
• Deprecate LazyFrame.profile() (#28275)
• Deprecate casts from non-nested dtypes into Lists (#28193)
• Deprecate bitwise ops between integers and booleans (#28186)
• Deprecate list/arr.to_struct() calls that don't pass field names (#28243)
• Rename missing_utf8_is_empty_string to empty_string_is_null (#28173)

🚀 Performance improvements

• Split multiplexers that directly scan from in-memory DataFrame (#28376)
• Make DNS cache global (#28352)
• Do not remove cache if predicates not pushed to all inputs (#28341)
• Environment variable for logging slow DNS lookup (#28211)
• Pre-partition on left, right and semi joins on hive partitioned data (#28374)
• Rewrite inner joins on hive partitioned data to a union of partitions filtered joins (#28327)
• Tighten redundant comparisons and propagate filter constraints (#27999)
• Canonicalize predicates (#28212)
• Remove excess memory copy in streaming IPC sink (#28141)
• Parallelize scan_iceberg resolve (#28168)
• Chunk-aware morsel splitting on single-file IO sink (#27950)
• Don't allocate for full_null() with small lengths (#28181)
• Use monotonic deque for rolling min_by/max_by (O(n)) (#27436)

✨ Enhancements

• Pre-partition group-by on hive keys (#28444)
• Add ewm_sum and ewm_sum_by #28151 (#28215)
• Serve stale records from object_store DNS cache (#28256)
• Make partition_hive an opt flag (#28345)
• Add scan_arrow_c_stream (#28340)
• When displaying IRExprs, only add parentheses when needed for disambiguation (#28319)
• Support Iceberg field initial-default in native scan_iceberg (#28324)
• Show only differing dtypes in assert_frame_equal error (#27816)
• Expose ewm and rolling *_by expressions in Python visitor (#28286)
• More accurate rolling moments (#28309)
• Remove hard block on native scan for Iceberg V3 tables (#28277)
• Add Series.degrees/radians and clarify trig functions use radians (#22961)
• Merge sorted with multikey (#28067)
• Add list expression which consistently packs elements together into new List type (#27990)
• Add read_database Arrow fast-path for "python-oracledb" (#28230)
• Optimize joins with redundant equi-join keys (#28017)
• Implement missing datetime options for CastColumnsPolicy (#28084)
• Add Expr.cat.to and Expr.cat.physical (#28096)
• Add POLARS_OOC_DISK_BUDGET_MB (#28045)
• Add build side preference parameter for join (#28154)

🐞 Bug fixes

• Avoid panic when union slice skips all rows (#28420)
• Solve panic in dt.replace when there were multiple chunks (#28437)
• Propagate is_scalar from the input to the output of .sort() and .sort_by() (#28438)
• Resolve CSV column names overwrite in DSL->IR conversion (#28383)
• Avoid IEJoin rewrite for Categorical comparisons (#28427)
• Do not rewrite sort().reverse() to sort(descending=True) when maintain_order=True (#28403)
• Ensure BinaryView offset+len does not exceed i32::MAX where possible (#28048)
• Invalid offset in strptime (#28388)
• Incorrect schema type for decimal <-> primitive division (#28373)
• Panic in in-memory CSEE handling (#28371)
• Fix offset in arrow ffi export of sliced struct arrays (#28369)
• Fix cross filter not applied with sink and CSE (#28297)
• Fix panic on projection pushdown with caches (#28280)
• Fix write_json() null values in Array columns being written incorrectly as null (#28330)
• Fix EntityTooSmall on sink_ipc to S3 (#28255)
• Raise error instead of silent wrapping for select(len()) (#28355)
• Float16 groupby aggregates (#28361)
• Respect lexical ordering of Categorical in top_k/bottom_k (#28359)
• Support dtype-list schema overrides in scan_csv (#28226)
• Resolve unknown type in fused multiply add (#28321)
• Honor aws_checksum_algorithm when provided (#28328)
• Remove usage of deprecated pyarrow.feather.read_table (#28323)
• Fix regression in sourcing HF_TOKEN (#28317)
• Raise on addition/subtraction between temporal and non-temporal Series (#28266)
• Avoid panic constructing Series from unaligned numpy arrays (#28120)
• Rewrite with_columns on empty df to select during DSL -> IR (#28298)
• Fix sink deadlock regression (#28296)
• Avoid panic when consumer of vertical concat is done (#28272)
• Harden IPC mmap API (#28258)
• Classify S3 region request failures as IO errors (#28225)
• Incorrect inner dtype in ArrayChunked::from_aligned_values (#28249)
• Raise on implode of Object dtype instead of creating invalid List(Object) (#28246)
• Return null not 0 for the first unbiased ewm_var/ewm_std value (#28235)
• Database appends with ADBC shouldn't require "CREATE" privileges unless the table is confirmed not to exist (#28228)
• Avoid slice pushdown panic on shared cache inputs (#28157)
• Incorrect dtype for Unknown right literal in arithmetic (#28184)
• Remove unnecessary unsafe Python object downcast (#28189)
• Normalize non-native byte order in numpy array construction (#28197)
• Use-after-free in numpy ufunc FFI (#28195)
• Unpickling for pl.when().then() (#28165)
• Reduce unknown casts (#28145)
• Consider a rolling_rank position invalid if ost.len() < min_samples (#28142)
• Incorrect broadcast with empty len in pl.concat_list (#28134)

📖 Documentation

• Update comparison page (#28418)
• Update GPU support documentation with the cudf-polars 26.06 release (#27830)
• Fix dev docs being canonical for SEO (#28306)
• Document experimental HDFS support on-premises (#28115)
• Add Series.degrees/radians and clarify trig functions use radians (#22961)
• Add polars-bio to community plugins (#28103)
• Add AWS Marketplace walkthrough to Cloud User Guide (#28214)
• Correct merge_sorted() docs also for DataFrame (#28183)
• Clarify DataFrame.remove combines predicates with AND (#28171)
• Update config reference (#28150)
• Correct that merge_sorted() null inputs should be nulls first (#28177)
• Clarify parts of the Polars Cloud and On-prem user guide (#28170)
• Add On-Premise release 0.6.3 to releases page (#28175)
• Update PolarsCloud snippets for 0.9.0 release (#28166)
• Fix to_titlecase incorrectly claiming alphanumeric separation (#28136)

📦 Build system

• Set the default dev profile to line-tables-only (#28358)
• Reduce binary size by optimizing for size in the SQL transpilation (#28336)

🛠️ Other improvements

• Update AI policy for comments (#28436)
• Fix flaky ordering expectation in top_k_by (#28435)
• Ignore all deprecation warnings in Python doctest (#28398)
• Re-work shuffle parameter for sample() (#27460)
• Ignore deprecation warnings on to_struct() in doctest (#28370)
• Update spin dependency to v0.10.1 (#28360)
• Bloat dispatch reduction (#28337)
• Show only differing dtypes in assert_frame_equal error (#27816)
• Accept IR in optimize (#28318)
• Annotate untyped module constants (#27907)
• Remove unencountered deny entries (#28260)
• Bump crossbeam-epoch dependency (#28259)
• Change object_store custom DNS resolver patch to rev-based (#28241)
• Mark shape tests as passing (#28133)
• Attribute annotations for *GroupBy (#27903)
• Clarify AI policy, explicitly forbid agents from interacting with our repository (#28206)
• Tighten first-time-contributor screenshot requirements (#28207)
• Covariant classinstmethod and attribute annotation (#27904)
• Ignore quickxml DoS rustsec (#28185)
• Update typos to v1.48.0 (#28162)

Thank you to all our contributors for making this release possible!
@0guban0v, @AnirudhRahul, @Bharath-970, @CodingSelim, @EndPositive, @Jesse-Bakker, @Kevin-Patyk, @LarryHu0217, @MarcoGorelli, @MatteoPossamai, @TNieuwdorp, @alex-h-sun, @alexander-beedie, @azimafroozeh, @borchero, @dancsi, @dependabot[bot], @dsprenkels, @harrywhalen, @jorenham, @kdn36, @makinzm, @malhotrashivam, @mdavis-xyz, @mikhail5555, @mkzung, @mroeschke, @nameexhaustion, @orlp, @r-brink, @raphaelroshan, @ritchie46, @tylerriccio33, @useredsa, @wence-, @yannbolliger, @zichen0116 and dependabot[bot]

⚠️ Deprecations

• Deprecate strict parameter of pl.concat, replace with new how='horizontal_extend' (#27965)

🚀 Performance improvements

• Add a sampled resolve mode for multi-file parquet metadata (#28111)
• Speed up small dtype series sums with a upcast sum kernel (#27958)
• Don't block on path expansion (#28073)

✨ Enhancements

• Close ResourceWarning leaks in database tests (#28066)

🐞 Bug fixes

• Incorrect sorted fast-path returning nan for grouped max (#28129)
• Fix panic on scan_parquet filter of fixed-size binary column (#28122)
• Fix decimal dynamic float cast (#28126)
• Fix pyiceberg key dot HDFS prefix filter (#28109)
• Fix projection pushdown panic on select(len()) after groupby (#28108)
• Fully resolve remaining ResourceWarning leaks in database/iceberg tests (#28107)
• Expiry time loading for AWS DeferredRefreshableCredentials (#28099)
• Close ResourceWarning leaks in database tests (#28066)
• Avoid panic on temporal extraction for datetime columns with nulls (#28054)
• Prevent panic in replace when old/new contain Expr or object dtype values (#27433)

📖 Documentation

• Fix dataset regression in the examples (#28131)
• Emphasize to generally not ever write Rust tests (#28082)
• Mention Polars skill in User Guide's LLM section (#28113)

🛠️ Other improvements

• Disallow usage of tokio::spawn in clippy (#28123)
• Improve Makefile with respect to venv robustness (#28110)
• Remove legacy prelude glob imports from leaf files (#28114)
• Skip pandas 3.0.4 due to pd.TimeDelta segfault (#28125)
• Update mypy to the new 2.x release (#28116)
• Ensure pyrefly checks run as part of make pre-commit (#28095)
• Fix test_select_explode_height_filter_order_by failure when POLARS_MAX_THREADS=2 (#28090)
• Add Morsel::height (#28060)

Thank you to all our contributors for making this release possible!
@0guban0v, @Kevin-Patyk, @TNieuwdorp, @alexander-beedie, @azimafroozeh, @dsprenkels, @kdn36, @nameexhaustion, @orlp, @raphaelroshan, @ritchie46 and @sar-cheng