rs-0.49.0

## 💥 Breaking changes

- Remove old streaming engine (#23103)

## 🚀 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

- Native implementation for Iceberg positional deletes (#23091)
- Remove old streaming engine (#23103)
- Make match\_chunks public (#23101)
- Implement StructFunction expressions in into\_py (#23022)
- 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)
- Add and test DataFrame equality functionality (#22865)
- Support descendingly-sorted values in search\_sorted() (#22825)
- Derive DSL schema (#22866)

## 🐞 Bug fixes

- Restrict custom `aggregate_function` in `pivot` to `pl.element()` (#23155)
- Don't leak `SourceToken` in in-memory sink linearize (#23201)
- 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)
- Don't create i128 scalars if dtype-128 is not set (#23118)
- 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)
- 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 `size_hint()` for `FlatIter` (#23010)
- 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)
- Fix cum\_min and cum\_max does not preserve inf or -inf values at series start (#22896)
- Setting `compat_level=0` for `sink_ipc` (#22960)
- Support arrow Decimal32 and Decimal64 types (#22954)
- Update arrow format (#22941)
- Fix filter pushdown to IO plugins (#22910)
- Improve numeric stability rolling\_mean\<f32> (#22944)
- 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)
- Correct `int_ranges` to raise error on invalid inputs (#22894)
- Set the sorted flag on Array after it is sorted (#22822)
- 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

- Update when\_then in user guide (#23245)
- Minor improvement to `cum_count` docstring example (#23099)
- Add missing entry for LazyFrame `__getitem__` (#22924)

## 📦 Build system

- 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

- Update Rust Polars versions (#23229)
- Change flake to use venv (#23219)
- Add `default_alloc` feature to `py-polars` (#23202)
- 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)
- Improve Series equality functionality and prepare for Python integration (#23136)
- Add PolarsPhysicalType and use it to dispatch into\_series (#23080)
- 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)
- Use a ref-counted `UniqueId` instead of `usize` for `cache_id` (#22984)
- Implement `Hash` and use `SpecialEq` for `RenameAliasFn` (#22989)
- Turn `list.eval` into an `AExpr` (#22911)
- Only check for unknown DSL fields if minor is higher (#22970)
- Don't enable `ir_serde` together with `serde` (#22969)
- Make dtype field on Logical non-optional (#22966)
- Add new (Frozen)Categories and CategoricalMapping (#22956)
- 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, @borchero, @bschoenmaeckers, @cmdlineluser, @coastalwhite, @deanm0000, @dsprenkels, @eitsupi, @florian-klein, @i1oveMyse1f, @ion-elgreco, @itamarst, @kdn36, @kutal10, @math-hiyoko, @mcrumiller, @mrkn, @mroeschke, @nameexhaustion, @nikaltipar, @orlp, @paskhaver, @ritchie46, @stijnherfst, @thomasfrederikhoeck and @zyctree