perf: optimize merge overlap check with coordinate cache#46
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The merge overlap check was O(n^2) with string parsing on every comparison: for each new merge region, all existing references were re-parsed from their string form (e.g. "A1:C3") into numeric coordinates. This caused measurable slowdown when adding 500+ merge regions. Add a `cached_coords` field (serde-skipped) to `MergeCells` that stores pre-parsed `(min_col, min_row, max_col, max_row)` tuples in parallel with the reference strings. The cache is lazily populated on first overlap check (handling worksheets deserialized from XML) and maintained incrementally on add/remove. Reference string shifting (row/col insert) invalidates the cache so it rebuilds on next use. This eliminates all string parsing from the hot path: overlap checks become pure numeric comparisons at 16 bytes per region, with negligible memory overhead for the common case (< 50 merge regions). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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리뷰 코멘트 공유드립니다.
참고로 로컬에서 PR 브랜치 기준 |
The cached_coords field is a runtime performance cache that is not serialized. With the derived PartialEq, two MergeCells with identical XML content could compare as unequal depending on whether the cache had been populated. Implement PartialEq manually to compare only count and merge_cells, making equality independent of cache state. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Code reviewNo issues found. Checked for bugs and CLAUDE.md compliance. |
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Summary
cached_coords: Vec<(u32, u32, u32, u32)>field toMergeCellswith#[serde(skip)]for zero serialization impactPerformance Impact
cell_name_to_coordinatesper region). For 500 sequential inserts, ~125,000 string-parsing operations.Changes
crates/sheetkit-xml/src/worksheet.rs: Addcached_coordsfield toMergeCellscrates/sheetkit-core/src/merge.rs:ensure_cache()helper + cached overlap checkcrates/sheetkit-core/src/stream.rs: Initialize cache in StreamWritercrates/sheetkit-core/src/workbook/sheet_ops.rs: Invalidate cache on row/col shiftsTest plan
cargo clippy --workspacecleancargo fmt --checkpass🤖 Generated with Claude Code