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perf: fix 104% regression in ExtractWorkflowNameFromFile by reducing scanner buffer allocation #30706

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Merged
pelikhan merged 2 commits into from
May 7, 2026
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perf: fix 104% regression in ExtractWorkflowNameFromFile by reducing scanner buffer allocation #30706

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Copilot May 6, 2026
fec5a9c
fix: reduce initial buffer allocation in fastParseTitleFromReader to …
Copilot May 7, 2026
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8 changes: 5 additions & 3 deletions pkg/cli/workflows.go
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Original file line number Diff line number Diff line change
Expand Up @@ -335,9 +335,11 @@ func filterMarkdownFilesWithFrontmatter(mdFiles []string) ([]string, error) {
// Returns an error if frontmatter is opened but never closed.
func fastParseTitleFromReader(r io.Reader) (string, error) {
scanner := bufio.NewScanner(r)
// Increase the max token size beyond the default 64 KB to handle files with
// large frontmatter values or long base64-encoded lines.
scanner.Buffer(make([]byte, 64*1024), 1024*1024)
// Use a small initial buffer (4 KB, matching the default scanner allocation)
// but allow growth up to 1 MB to handle files with large frontmatter values
// or long base64-encoded lines. Keeping the initial size small avoids a
// costly 64 KB heap allocation on every call.
scanner.Buffer(make([]byte, 4*1024), 1024*1024)
firstLine := true
inFrontmatter := false
for scanner.Scan() {
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