fix: inefficient merge check for large amount of merged cells#2920
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3ximus wants to merge 2 commits intoexceljs:masterfrom
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fix: inefficient merge check for large amount of merged cells#29203ximus wants to merge 2 commits intoexceljs:masterfrom
3ximus wants to merge 2 commits intoexceljs:masterfrom
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privatecoder
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Sep 24, 2025
nfcampos
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Nov 26, 2025
…nce O(n²) → O(n) The original implementation iterated through ALL existing merges for each new merge operation, causing O(n²) complexity that became extremely slow with many merges (30,000 merges took 1.5 minutes). This fix checks individual cells directly via the `cell.isMerged` property instead, reducing complexity to O(m) where m is the merge area size. Performance improvement with 10,000 merges: 6464ms → 34ms (190x faster) Original PR: exceljs#2920 Based on: exceljs#2691 Co-Authored-By: aorsten <[email protected]> Co-Authored-By: 3ximus <[email protected]>
nfcampos
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Nov 26, 2025
…jPYqutcWxrbar2r9hBK perf: Adopt upstream PR exceljs#2920 - Optimize merged cells performance O(n²) → O(n)
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This pull request is the same as this stale one #2691 with the comments applied to it. I would really like to see this merge.
Thank you