# Polars 1.4.0 — Python Polars 1.4.0

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2024-08-02
- Version: 1.4.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.4.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.4.0

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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- **changed** — Delay selection expansion
- **changed** — Optimize strings slices
- **changed** — Make .dt.weekday 20x faster
- **changed** — Shrink MemSliceInner enum
- **changed** — Push down slice with non-zero offset to Parquet
- **changed** — Reduce copy in MemSlice
- **added** — Add nested SQL join support
- **added** — Add support for binary size method to Expr and Series bin namespace
- **added** — Add IO plugins
- **added** — Add SQL interface support for PostgreSQL dollar-quoted string literals
- **changed** — Allow for parsing parquet file where the time zone is stored as lowercase utc
- **fixed** — Respect strict argument
- **fixed** — Multi-output column expressions in frame sort method
- **fixed** — Fix Asof join by schema
- **fixed** — Set default flags for FFI plugin
- **fixed** — Fix glob resolution for Hugging Face
- **fixed** — Several parquet reader/writer regressions
- **fixed** — Incorrect filter on categorical columns from parquet files
- **fixed** — SQL COUNT(DISTINCT x) should not include NULL values
- **fixed** — Default to None in pycapsule interface export

##### 🚀 Performance improvements

- Delay selection expansion (#18011)
- Optimize strings slices (#17996)
- Make `.dt.weekday` 20x faster (#17992)
- Shrink `MemSliceInner` enum (#17991)
- Push down slice with non-zero offset to Parquet (#17972)
- Reduce copy in `MemSlice` (#17983)

##### ✨ Enhancements

- Add nested SQL join support (#18006)
- Push down slice with non-zero offset to Parquet (#17972)
- Add support for binary `size` method to Expr and Series "bin" namespace (#17924)
- IO plugins (#17939)
- Add `SQL` interface support for PostgreSQL dollar-quoted string literals (#17940)
- Allow for parsing parquet file where the time zone is stored as lowercase "utc" (#17925)

##### 🐞 Bug fixes

- Add nested SQL join support (#18006)
- Respect `strict` argument (#17990)
- Multi-output column expressions in frame `sort` method (#17947)
- Fix Asof join by schema (#17988)
- Set default flags for FFI plugin (#17984)
- Fix glob resolution for Hugging Face (#17958)
- Several parquet reader/writer regressions (#17941)
- Incorrect filter on categorical columns from parquet files (#17950)
- SQL `COUNT(DISTINCT x)` should not include NULL values (#17930)
- Default to `None` in pycapsule interface export (#17922)

##### 📖 Documentation

- Fix aggregation guide discrepancies (#18003)
- Ensure `last` is never ambiguous with `max` (#17962)
- Documentation for Arrow PyCapsule interface integration (#17935)
- Fix Hugging Face link in user guide (#17943)

##### 🛠️ Other improvements

- Add unit tests for `str.contains_any` and `str.replace_many` (#17961)
- Suggest `allow_null` as replacement (#17969)
- Remove apply\_generic, use unary\_elementwise (#17902)
- Add general filters in Parquet (#17910)

Thank you to all our contributors for making this release possible!
@JamesCE2001, @MarcoGorelli, @alexander-beedie, @coastalwhite, @deanm0000, @deepyaman, @dependabot, @dependabot[bot], @henryharbeck, @kylebarron, @nameexhaustion, @ritchie46 and @wangxiaoying