# Polars 1.25.2 — Python Polars 1.25.2

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2025-03-15
- Version: 1.25.2
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.25.2
- Permalink: https://whatsnew.fyi/product/polars/releases/1.25.2

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **added** — Add lazy sinks
- **added** — Add PartitionByKey for new streaming sinks
- **added** — Add a config option to specify the default engine to attempt to use during lazyframe calls
- **added** — Add len method to arr
- **added** — Add new PartitionMaxSize sink
- **added** — Add NDJSON source to new streaming engine
- **changed** — Enable common subplan elimination across plans in collect_all
- **changed** — Implement linear-time rolling_min/max
- **changed** — Improve InputIndependentSelect by delegating to InMemorySourceNode
- **changed** — Add support for rolling_(sum/min/max) for booleans through casting
- **changed** — Support multi-column sort for all nested types and nested search-sorted
- **changed** — Enable joins on list/array dtypes
- **changed** — Stabilize Enum datatype
- **changed** — Enable new streaming memory sinks by default
- **changed** — Support engine callback for LazyFrame.profile
- **fixed** — Fix lazy schema for truediv ops involving List/Array dtypes
- **fixed** — Fix error due to race condition in file cache
- **fixed** — Clear NaNs due to zero-weight division in rolling var/std
- **fixed** — New streaming multiscan deadlock
- **fixed** — Fix deadlock in cache + hconcat

##### 🏆 Highlights

- Enable common subplan elimination across plans in `collect_all` (#21747)
- Add lazy sinks (#21733)
- Add `PartitionByKey` for new streaming sinks (#21689)
- Enable new streaming memory sinks by default (#21589)

##### 🚀 Performance improvements

- Implement linear-time rolling\_min/max (#21770)
- Improve InputIndependentSelect by delegating to InMemorySourceNode (#21767)
- Enable common subplan elimination across plans in `collect_all` (#21747)
- Allow elementwise functions in recursive lowering (#21653)
- Add primitive single-key hashtable to new-streaming join (#21712)
- Remove unnecessary black\_boxes in Kahan summation (#21679)
- Box large enum variants (#21657)
- Improve join performance for new-streaming engine (#21620)
- Pre-fill caches (#21646)
- Optimize only a single cache input (#21644)
- Collect parquet statistics in one contiguous buffer (#21632)
- Update Cargo.lock (mainly for zstd 1.5.7) (#21612)
- Don't maintain order when maintain\_order=False in new streaming sinks (#21586)
- Pre-sort groups in group-by-dynamic (#21569)

##### ✨ Enhancements

- Add support for rolling\_(sum/min/max) for booleans through casting (#21748)
- Support multi-column sort for all nested types and nested search-sorted (#21743)
- Add lazy sinks (#21733)
- Add `PartitionByKey` for new streaming sinks (#21689)
- Fix replace flags (#21731)
- Add `mkdir` flag to sinks (#21717)
- Enable joins on list/array dtypes (#21687)
- Add a config option to specify the default engine to attempt to use during lazyframe calls (#20717)
- Support all elementwise functions in IO plugin predicates (#21705)
- Stabilize Enum datatype (#21686)
- Support Polars int128 in from arrow (#21688)
- Use FFI to read dataframe instead of transmute (#21673)
- Enable new streaming memory sinks by default (#21589)
- Cloud support for new-streaming scans and sinks (#21621)
- Add len method to arr (#21618)
- Closeable files on unix (#21588)
- Add new `PartitionMaxSize` sink (#21573)
- Support engine callback for `LazyFrame.profile` (#21534)
- Dispatch new-streaming CSV negative slice to separate node (#21579)
- Add NDJSON source to new streaming engine (#21562)
- Support passing `token` in `storage_options` for GCP cloud (#21560)

##### 🐞 Bug fixes

- Expose and document partitions (#21765)
- Fix lazy schema for truediv ops involving List/Array dtypes (#21764)
- Fix error due to race condition in file cache (#21753)
- Clear NaNs due to zero-weight division in rolling var/std (#21761)
- Allow init from BigQuery Arrow data containing ExtensionType cols with irrelevant metadata (#21492)
- Disallow cast from boolean to categorical/enum (#21714)
- Don't check sortedness in `join_asof` when 'by' groups supplied, but issue warning (#21724)
- Incorrect multithread path taken for aggregations (#21727)
- Disallow cast to empty Enum (#21715)
- Fix `list.mean` and `list.median` returning Float64 for temporal types (#21144)
- Incorrect (FixedSize)ListArrayBuilder gather implementation (#21716)
- Always fallback in SkipBatchPredicate (#21711)
- New streaming multiscan deadlock (#21694)
- Ensure new-streaming join BuildState is correct even if never fed morsels (#21708)
- IO plugin; support empty iterator (#21704)
- Support nulls in multi-column sort (#21702)
- Window function check length of groups state (#21697)
- Support 128 sum reduction on new streaming (#21691)
- IPC round-trip of list of empty view with non-empty bufferset (#21671)
- Variance can never be negative (#21678)
- Incorrect loop length in new-streaming group by (#21670)
- Right join on multiple columns not coalescing left\_on columns (#21669)
- Casting Struct to String panics if n\_chunks > 1 (#21656)
- Fix`Future attached to different loop` error on `read_database_uri` (#21641)
- Fix deadlock in cache + hconcat (#21640)
- Properly handle phase transitions in row-wise sinks (#21600)
- Enable new streaming memory sinks by default (#21589)
- Always use global registry for object (#21622)
- Check enu

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.25.2]_