Changelog¶

1.0.0 (2026-07-06)¶

auto_dict plan lost in parallel merge: ColumnarEngine::new() defaulted to auto_dict: false, making auto_dict_upgrade() a no-op. Fixed by using ColumnarEngine::with_plan(est, plan) to carry the build plan forward.
Text field parsing in bounded path: The parser was capturing whitespace-only text nodes as field values instead of looking for <TextValue> children. Fixed to correctly consume TextValue inner text.
Stream engine column discovery: Engine used first-row columns as schema; sparse columns appearing only in later rows caused crashes. Schema is now discovered across all rows.
Publishing workflow missing columnar feature: maturin build --features mmap risked overriding pyproject.toml's feature list and silently dropping columnar from the published wheel. CI now builds from pyproject.toml defaults.

prefault parameter: All engines accept prefault: bool. True = MADV_WILLNEED (speed), False = MADV_SEQUENTIAL (lower RSS). Defaults: True for columnar/parallel, False for bounded.
Parallel engine profiling: get_par_profile() returns nanosecond timing for split-scan, off-GIL parse, and on-GIL assembly phases (gated behind profile Cargo feature).
Bounded mode RSS rewrite: Mmap used only for initial split scan, then dropped. Chunks read via File::seek/read_exact. Peak RSS tracks the memory= budget, not the file size.
sort_columns() on engine: Ensures all batch engines produce identical column order for schema-match fast path in concat_tables().

Splitter SIMD optimization: next_row_start() searches for <tag in one memmem::find pass instead of memchr(b'<') (24M iterations to 465k matches). Split phase 40% faster. Total parallel throughput improved 22% (327 to 472 MB/s on 533 MB real file).
find_special_regions() single-pass: Scans once for b"<!" prefix instead of two separate scans for <!-- and <![CDATA[.
concat_tables() schema fast path: Skips promote_options='default' when schemas already match.

Build features (columnar, mmap) now enabled by default in pyproject.toml. profile remains opt-in.
Removed --features mmap from CI publishing workflow.
Added docs/performance.md with environment block, per-engine speed tables, memory decomposition, and throughput ceiling.
Correctness harness validates all engines against stream oracle across 29 test cases plus 465k-row real-file cross-check.
README restyled to match seoslug format: quick start first, narrative "why" section, comparison table, features table, framework support, --- section rulers.