Python Polars 1.31.0-beta.1

💥 Breaking changes

• Remove old streaming engine (#23103)

⚠️ Deprecations

• Deprecate allow_missing_columns in scan_parquet in favor of missing_columns (#22784)

🚀 Performance improvements

• Improve streaming groupby CSE (#23092)
• Move row index materialization in post-apply to occur after slicing (#22995)
• Add first_(true|false)_idx to BooleanChunked and use in bool arg_(min|max) (#22907)
• Don't go through row encoding for most types on index_of (#22903)
• Optimise low-level null scans and arg_max for bools (when chunked) (#22897)
• Optimize multiscan performance (#22886)

✨ Enhancements

• DataType expressions in Python (#23167)
• Native implementation for Iceberg positional deletes (#23091)
• Remove old streaming engine (#23103)
• Basic implementation of DataTypeExpr in Rust DSL (#23049)
• Add required: bool to ParquetFieldOverwrites (#23013)
• Support serializing name.map_fields (#22997)
• Support serializing Expr::RenameAlias (#22988)
• Remove duplicate verbose logging from FetchedCredentialsCache (#22973)
• Add keys column in finish_callback (#22968)
• Add extra_columns parameter to scan_parquet (#22699)
• Add CORR function to polars SQL (#22690)
• Add per partition sort and finish callback to sinks (#22789)
• Support descendingly-sorted values in search_sorted() (#22825)
• Derive DSL schema (#22866)

🐞 Bug fixes

• Fix panic reading empty parquet with multiple boolean columns (#23159)
• Raise ComputeError instead of panicking in truncate when mixing month/week/day/sub-daily units (#23176)
• Materialize list.eval with unknown type (#23186)
• Only set sorting flag for 1st column with PQ SortingColumns (#23184)
• Typo in AExprBuilder (#23171)
• Null return from var/std on scalar column (#23158)
• Support Datetime broadcast in list.concat (#23137)
• Ensure projection pushdown maintains right table schema (#22603)
• Add Null dtype support to arg_sort_by (#23107)
• Raise error by default on invalid CSV quotes (#22876)
• Fix group_by mean and median returning all nulls for Decimal dtype (#23093)
• Fix hive partition pruning not filtering out __HIVE_DEFAULT_PARTITION__ (#23074)
• Fix AssertionError when using scan_delta() on AWS with storage_options (#23076)
• Fix deadlock on collect(background=True) / collect_concurrently() (#23075)
• Incorrect null count in rolling_min/max (#23073)
• Preserve file:// in LazyFrame node traverser (#23072)
• Respect column order in register_io_source schema (#23057)
• Don't call unnest for objects implementing __arrow_c_array__ (#23069)
• Incorrect output when using sort with group_by and cum_sum (#23001)
• Implement owned arithmetic for Int128 (#23055)
• Do not schema-match structs with different field counts (#23018)
• Fix confusing error message on duplicate row_index (#23043)
• Add include_nulls to Agg::Count CSE check (#23032)
• View buffer exceeding 2^32 - 1 bytes in concatenate_view (#23017)
• Fix incorrect result selecting pl.len() from scan_csv with skip_lines (#22949)
• Allow for IO plugins with reordered columns in streaming (#22987)
• Method str.zfill was inconsistent with Python and pandas when string contained leading '+' (#22985)
• Integer underflow in propagate_nulls (#22986)
• Setting compat_level=0 for sink_ipc (#22960)
• Narrow return type for DataType.is_, improve Pyright's type completeness from 69% to 95% (#22962)
• Support arrow Decimal32 and Decimal64 types (#22954)
• Guard against dictionaries being passed to projection keywords (#22928)
• Update arrow format (#22941)
• Fix filter pushdown to IO plugins (#22910)
• Improve numeric stability rolling_mean<f32> (#22944)
• Guard against invalid nested objects in 'map_elements' (#22932)
• Allow subclasses in type equality checking (#22915)
• Return early in pl.Expr.__array_ufunc__ when only single input (#22913)
• Add inline implodes in type coercion (#22885)
• Add {top, bottom}_k_by to Series (#22902)
• Correct int_ranges to raise error on invalid inputs (#22894)
• Don't silently overflow for temporal casts (#22901)
• Fix error using write_csv with storage_options (#22881)
• Schema resolution .over(mapping_strategy="join") with non-aggregations (#22875)
• Ensure rename behaves the same as select (#22852)

📖 Documentation

• Document aggregations that return identity when there's no non-null values, suggest workaround for those who want SQL-standard behaviour (#23143)
• Fix reference to non-existent Expr.replace_all in replace_strict docs (#23144)
• Fix typo on pandas comparison page (#23123)
• Minor improvement to cum_count docstring example (#23099)
• Add missing DataFrame.__setitem__ to API reference (#22938)
• Add missing entry for LazyFrame __getitem__ (#22924)
• Add missing top_k_by and bottom_k_by to Series reference (#22917)

📦 Build system

• Update pyo3 and numpy crates to version 0.25 (#22763)
• Actually disable ir_serde by default (#23046)
• Add a feature flag for serde_ignored (#22957)
• Fix warnings, update DSL version and schema hash (#22953)

🛠️ Other improvements

• Added more descriptive error message by replacing FixedSizeList with Array (#23168)
• Connect Python assert_series_equal() to Rust back-end (#23141)
• Refactor skip_batches to use AExprBuilder (#23147)
• Use ir_serde instead of serde for IRFunctionExpr (#23148)
• Separate FunctionExpr and IRFunctionExpr (#23140)
• Remove AExpr::Alias (#23070)
• Add components for Iceberg deletion file support (#23059)
• Feature gate StructFunction::JsonEncode (#23060)
• Propagate iceberg position delete information to IR (#23045)
• Add environment variable to get Parquet decoding metrics (#23052)
• Turn pl.cumulative_eval into its own AExpr (#22994)
• Add make test-streaming (#23044)
• Move scan parameter parsing for parquet to reusable function (#23019)
• Prepare deltalake 1.0 (#22931)
• Implement Hash and use SpecialEq for RenameAliasFn (#22989)
• Turn list.eval into an AExpr (#22911)
• Fix CI for latest pandas-stubs release (#22971)
• Add a CI check for DSL schema changes (#22898)
• Add schema parameters to expr.meta (#22906)
• Update rust toolchain in nix flake (#22905)
• Update toolchain (#22859)

Thank you to all our contributors for making this release possible!
@Athsus, @DahaoALG, @FabianWolff, @JakubValtar, @Kevin-Patyk, @MarcoGorelli, @SanjitBasker, @alexander-beedie, @bschoenmaeckers, @coastalwhite, @deanm0000, @dsprenkels, @eitsupi, @florian-klein, @i1oveMyse1f, @ion-elgreco, @itamarst, @kdn36, @kutal10, @mroeschke, @nameexhaustion, @nikaltipar, @orlp, @paskhaver, @ritchie46, @stijnherfst and @thomasfrederikhoeck