Polars: py-0.20.19 Release

🚀 Performance improvements

• Replace std::thread spawn with tokio block_in_place (#15517)
• speed up offset_by when a single offset is passed (#15493)
• Avoid allocation in the hot path for struct JSON serialization (#15449)

✨ Enhancements

• Support list group-by of non numeric lists (#15540)
• add business_day_count function (#15512)
• Add SQL support for MEDIAN aggfunc (#15519)
• Implement string, boolean and binary dtype in top_k (#15488)
• Add SQL support for TRUNCATE TABLE command (#15513)
• Add SQL support for GREATEST and LEAST (#15511)
• Allow specifying Hive schema in read/scan_parquet (#15434)
• Implements agg_list for NullChunked (#15439)

🐞 Bug fixes

• dot product of two integer series is cast to float (#15502)
• Resolve function names and prune all aliases. (#15522)
• Pass skip_rows_after_header to pyarrow csv reader (#15533)
• No longer error when schema_overrides contains nonexistent columns (#15528)
• list.get should take validity into account (#15516)
• block decimal in streaming (#15520)
• group_by partitioned with literal Series panic (#15487)
• Initialize validity for GroupsProxy::Slice windows (#15509)
• Fix struct name resolving (#15507)
• pow return type evaluation (#15506)
• Address issue with read_database draining iter_batches early (#15504)
• Allow selectors inside frame-level .filter() (#15445)
• Don't prune alias in AnonymousFunction subtree (#15453)
• Raise if pass a negative n into clear (#15432)
• Fix deadlock in async parquet scan (#15440)

📖 Documentation

• Update leftover references of by parameter to group_by in DataFrame/LazyFrame.upsample/group_by_dynamic/rolling (#15527)
• Add make docs command, DataType docs/layout tweak, minor README updates (#15386)
• Add example for Series.list.median. (#15451)

🛠️ Other improvements

• Remove unused code paths in read_parquet (#15532)
• Organize utils for I/O functionality (#15529)
• Remove private DataFrame._read classmethods (#15521)
• Move dedicated inference code out of io.database executor module (#15526)
• Add unstable warning to hive_schema functionality (#15508)

Thank you to all our contributors for making this release possible! @CanglongCl, @ChayimFriedman2, @MarcoGorelli, @alexander-beedie, @cmdlineluser, @dependabot, @dependabot[bot], @henryharbeck, @mbuhidar, @nameexhaustion, @reswqa, @ritchie46, @rob-sil and @stinodego