Polars Rust 0.55.1：性能提升与多项新功能

This Releases' DSL matches Python 1.43.2.

🚀 Performance improvements

• Pushdown len() to concat/union inputs (#28570)
• Optimize not(bool_f) to not_bool_f (#28474)
• Split multiplexers that directly scan from in-memory DataFrame (#28376)
• Make DNS cache global (#28352)
• Do not remove cache if predicates not pushed to all inputs (#28341)
• Environment variable for logging slow DNS lookup (#28211)
• Pre-partition on left, right and semi joins on hive partitioned data (#28374)
• Rewrite inner joins on hive partitioned data to a union of partitions filtered joins (#28327)
• Tighten redundant comparisons and propagate filter constraints (#27999)
• Canonicalize predicates (#28212)
• Remove excess memory copy in streaming IPC sink (#28141)
• Parallelize scan_iceberg resolve (#28168)
• Chunk-aware morsel splitting on single-file IO sink (#27950)
• Don't allocate for full_null() with small lengths (#28181)
• Use monotonic deque for rolling min_by/max_by (O(n)) (#27436)
• Add a sampled resolve mode for multi-file parquet metadata (#28111)
• Speed up small dtype series sums with a upcast sum kernel (#27958)
• Don't block on path expansion (#28073)
• Add bytes-based concurrency control for cloud IO (#27924)
• Stop flushing multiplexer on phase change (#28013)
• Prevent empty chunks from triggering copy in rechunk (#27953)
• Improve performance of struct unnest inside list eval on streaming (#27905)

✨ Enhancements

• Add struct.drop() (#28666)
• Improve error message when CSV name de-duplication fails (#28658)
• Always keep first metadata per source for Parquet (#28661)
• Improve plan-time row estimates for multi-file parquet scans (#28380)
• Serialize and deserialize SinkTypeIR::Partitioned (#28112)
• Add infer_schema_files parameter to scan_csv (#28440)
• Support reading IEEE 754 total order Parquet column order (#27896)
• Expose more Expr nodes for cudf_polars (pt 2) (#28404)
• Allow callback sinks on cloud (#28458)
• Pre-partition group-by on hive keys (#28444)
• Add ewm_sum and ewm_sum_by #28151 (#28215)
• Serve stale records from object_store DNS cache (#28256)
• Expose more expr nodes for cudf-polars (#28117)
• Make partition_hive an opt flag (#28345)
• When displaying IRExprs, only add parentheses when needed for disambiguation (#28319)
• Show only differing dtypes in assert_frame_equal error (#27816)
• Add Clone to SpillFrame/Token (#28302)
• Add Series.degrees/radians and clarify trig functions use radians (#22961)
• Merge sorted with multikey (#28067)
• Add list expression which consistently packs elements together into new List type (#27990)
• Construct pyarrow predicates via PyO3 instead of eval str (#27271)
• Optimize joins with redundant equi-join keys (#28017)
• Implement missing datetime options for CastColumnsPolicy (#28084)
• Add Expr.cat.to and Expr.cat.physical (#28096)
• Add POLARS_OOC_DISK_BUDGET_MB (#28045)
• Close ResourceWarning leaks in database tests (#28066)
• Expose IRFunctionExpr::Fused in the python node visitor (#27889)
• Deprecate casts from string to temporal dtypes (#28056)
• Add naive out-of-core spilling to Polars (#27998)
• Add experimental strict mode (#28023)
• Optimize non-negative len and null_count comparisons (#28002)
• Optimize len and null_count comparisons (#27727)
• Support SQL's implicit JOIN syntax (#27890)
• Sample from bivariate distribution for spill context Thompson sampling (#27973)
• Add Expr.is_sorted (#26708)
• Add suggestions in wrong api usage or mismatched column names (#27954)
• Add external object_store support for non-native schemes (#27871)
• Skip Delta files and parquet row groups using per-field struct statistics (#27887)
• Add re-registration of OOC SpillTokens (#27909)
• Improve IR sortedness detection for with_row_index and explode (#27875)
• Add DataFrame.is_sorted() (#27870)

🐞 Bug fixes

• Don't hand IO plugins a predicate they cannot evaluate (#28643)
• Don't hang or crash on sqrt/cbrt/pct_change/ewm_* with a Struct column (#28696)
• Raise on overflow in Decimal sum instead of silently wrapping (#28688)
• Preserve nulls when importing Arrow maps (#28680)
• Propagate null by column values in rolling_*_by (#27367)
• Fix self-referencing field in struct.with_fields with over (#28678)
• Fix Arrow buffer offset for Utf8 and Binary (#28662)
• Clamp group-by slice offset (#28579)
• Ensure categorical fill_null(strategy="min"/"max") uses lexical min/max (#28636)
• Release the GIL while resolving the schema in __arrow_c_stream__ (#28642)
• Fix data corruption on Series from nested Arrow LargeList (#28632)
• Properly propagate enum metadata for iceberg column mapping (#28580)
• Correctly write parquet field IDs for enums and categoricals (#28581)
• Fix arrow C interop binview offset (#28623)
• Fix duplicate hive values in hive pre-partition rewrite (#28621)
• Double-counted offset for Arrow export of sliced Series(Array) (#28602)
• Struct/List/Array equality handling in sort and join (#28601)
• Use try_new in StructArray construction in polars-json (#27489)
• Raise ComputeError instead of panicking in repeat_by when output exceeds IdxSize::MAX (#27892)
• Run type coercion pass on pivot's internally generated group_by (#27897)
• More careful slice pushdown into joins (#28578)
• Preserve ordering in sliced unions (#28576)
• Drop input sortedness when casting to a string (#28574)
• Clear sortedness flags in StringChunked substring kernels (#28573)
• Bad mask handling when reading optional parquet column (#28547)
• Any operation on Unknown(Int) and Unknown(Float) should result in Unknown(Float) (#28545)
• Flip nulls_last after Expr.reverse() (#28572)
• Fix high blocking thread use in sink_parquet with async local path (#28543)
• Serialize LazyFrames backed by bytes (#28568)
• Release GIL in SQLContext.execute() (#28549)
• Propagate nulls_last in function_expr_sortedness (#28544)
• Incorrect slicing when a join requires sorting (#28541)
• Fix panic on self join of scan_delta / scan_iceberg (#28468)
• Decrement ParkGroup worker count when worker exits (#28492)
• Add missing Send bounds in Connector (#28497)
• Fix UB on first/last_non_null with empty chunk (#28495)
• Do not CSE non-column height expr on streaming engine (#28480)
• Propagate adjusted sortedness through Gather (#28493)
• Deduplicate the expression equality checks (#28483)
• Address 3VL issue with SQL NOT IN interaction with NULL values and joins (#28484)
• Use total comparison in Expr literal values (#28482)
• Ensure SQL SUM and CORR aggregates return NULL for all-null inputs, add TOTAL (#28475)
• Share null_count_dtype helper between Delta and Iceberg, fixing SchemaError (#28479)
• Remove non-output columns from the equi-join and semi/anti-join operators (#28446)
• Fix dropped slice on multiple unions (#28477)
• Fix in-memory engine incorrect slice on maintain order join (#28478)
• Check join schema by position (#28455)
• Block predicate pushdown past overwritten window keys (#28429)
• Avoid panic when union slice skips all rows (#28420)
• Solve panic in dt.replace when there were multiple chunks (#28437)
• Propagate is_scalar from the input to the output of .sort() and .sort_by() (#28438)
• Insert missing coercions from Unknown(_) in list/array arithmetic (#28411)
• Resolve CSV column names overwrite in DSL->IR conversion (#28383)
• Avoid IEJoin rewrite for Categorical comparisons (#28427)
• Do not rewrite sort().reverse() to sort(descending=True) when maintain_order=True (#28403)
• Propagate bigidx to polars-plan from polars (#28396)
• Ensure BinaryView offset+len does not exceed i32::MAX where possible (#28048)
• Invalid offset in strptime (#28388)
• Incorrect schema type for decimal <-> primitive division (#28373)
• Panic in in-memory CSEE handling (#28371)
• Apply same type coercion to IsBetween as binary comparisons (#28300)
• Fix offset in arrow ffi export of sliced struct arrays (#28369)