# Polars 1.38.0 — Python Polars 1.38.0

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2026-02-04
- Version: 1.38.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.38.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.38.0

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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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- **deprecated** — Deprecate retries=n in favor of storage_options={"max_retries": n}
- **changed** — Enable zero-copy object_store put upload for IPC sink
- **changed** — Resolve file schema's and metadata concurrently
- **changed** — Run elementwise CSEE for the streaming engine
- **changed** — Disable morsel splitting for fast-count on streaming engine
- **changed** — Implement streaming decompression for scan_ndjson and scan_lines
- **changed** — Improve string slicing performance
- **changed** — Refactor scan_delta to use python dataset interface
- **changed** — Add dedicated kernel for group-by arg_max/arg_min
- **added** — Add streaming merge-join
- **changed** — Generalize Bitmap::new_zeroed opt for Buffer::zeroed
- **changed** — Reduce fs stat calls in path expansion
- **changed** — Lower streaming group_by n_unique to unique().len()
- **fixed** — Avoid OOM for scan_ndjson and scan_lines if input is compressed and negative slice
- **added** — Support anonymous agg in-mem
- **added** — Add unstable arrow_schema parameter to sink_parquet
- **added** — Allow quantile to compute multiple quantiles at once
- **added** — Allow empty LazyFrame in LazyFrame.group_by(...).map_groups
- **added** — Add scan_lines
- **added** — Support regex in str.split
- **added** — Add nulls support for all rolling_by operations

##### ⚠️ Deprecations

- Deprecate `retries=n` in favor of `storage_options={"max_retries": n}` (#26155)

##### 🚀 Performance improvements

- Enable zero-copy object\_store `put` upload for IPC sink (#26288)
- Resolve file schema's and metadata concurrently (#26325)
- Run elementwise CSEE for the streaming engine (#26278)
- Disable morsel splitting for fast-count on streaming engine (#26245)
- Implement streaming decompression for scan\_ndjson and scan\_lines (#26200)
- Improve string slicing performance (#26206)
- Refactor `scan_delta` to use python dataset interface (#26190)
- Add dedicated kernel for group-by `arg_max/arg_min` (#26093)
- Add streaming merge-join (#25964)
- Generalize Bitmap::new\_zeroed opt for Buffer::zeroed (#26142)
- Reduce fs stat calls in path expansion (#26173)
- Lower streaming group\_by n\_unique to unique().len() (#26109)

##### ✨ Enhancements

- Avoid OOM for scan\_ndjson and scan\_lines if input is compressed and negative slice (#26396)
- Support annoymous agg in-mem (#26376)
- Add unstable `arrow_schema` parameter to `sink_parquet` (#26323)
- Improve error message formatting for structs (#26349)
- Remove parquet field overwrites (#26236)
- Enable zero-copy object\_store `put` upload for IPC sink (#26288)
- Improved disambiguation for qualified wildcard columns in SQL projections (#26301)
- Expose `upload_concurrency` through env var (#26263)
- Allow quantile to compute multiple quantiles at once (#25516)
- Allow empty LazyFrame in `LazyFrame.group_by(...).map_groups` (#26275)
- Use delta file statistics for batch predicate pushdown (#26242)
- Add streaming UnorderedUnion (#26240)
- Implement compression support for sink\_ndjson (#26212)
- Add unstable record batch statistics flags to `{sink/scan}_ipc` (#26254)
- Support CSE for python UDFs on the same address (#26253)
- Cloud retry/backoff configuration via `storage_options` (#26204)
- Use same sort order for expanded paths across local / cloud / directory / glob (#26191)
- Add streaming merge-join (#25964)
- Serialize optimization flags for cloud plan (#26168)
- Add compression support to write\_csv and sink\_csv (#26111)
- Add `scan_lines` (#26112)
- Support regex in `str.split` (#26060)
- Add unstable IPC Statistics read/write to `scan_ipc`/`sink_ipc` (#26079)
- Add unstable `height` parameter to `DataFrame`/`LazyFrame` (#26014)
- Remove old partition sink API (#26100)
- Expose ArrowStreamExportable on python collect batches iterator (#26074)
- Add nulls support for all rolling\_by operations (#26081)

##### 🐞 Bug fixes

- Correct off-by-one in RLE row counting for nullable dictionary-encoded columns (#26411)
- Support very large integers in env var limits (#26399)
- Fix PlPath panic from incorrect slicing of UTF8 boundaries (#26389)
- Fix Float dtype for spearman correlation (#26392)
- Fix optimizer panic in right joins with type coercion (#26365)
- Don't serialize retry config from local environment vars (#26289)
- Fix `PartitionBy` with scalar key expressions and `diff()` (#26370)
- Add {Float16, Float32} -> Float32 lossless upcast (#26373)
- Fix panic using `with_columns` and `collect_all` (#26366)
- Add multi-page support for writing dictionary-encoded Parquet columns (#26360)
- Ensure slice advancement when skipping non-inlinable values in `is_in` with inlinable needles (#26361)
- Pin `xlsx2csv` version temporarily (#26352)
- Bugs in ViewArray total\_bytes\_len (#26328)
- Overflow in i128::abs in Decimal fits check (#26341)
- Make Expr.hash on Categorical mapping-independent (#26340)
- Clone shared GroupBy node before mutation in physical plan creation (#26327)
- Fixed "sheet\_name" typing for `read_ods` and `read_excel` (#26317)
- Improve Polars dtype inference from Python `Union` typing (#26303)
- Consider the "current location" of an item when computing `rolling_rank_by` (#26287)
- Reset `is_count_star` flag between queries in collect\_all (#26256)
- Fix incorrect is\_between filter on scan\_parquet (#26284)
- Make polars compatibl

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.38.0]_