refactor(core): speed up diff calculation significantly #20731
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natewill wants to merge 5 commits intoanomalyco:devfrom
Open
refactor(core): speed up diff calculation significantly #20731natewill wants to merge 5 commits intoanomalyco:devfrom
natewill wants to merge 5 commits intoanomalyco:devfrom
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natewill
commented
Apr 2, 2026
| const diffFull = Effect.fnUntraced(function* (from: string, to: string) { | ||
| return yield* locked( | ||
| Effect.gen(function* () { | ||
| const catFile = Effect.fnUntraced( |
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We can’t use the normal git() helper here because git cat-file --batch needs us to write refs to stdin and read raw stdout bytes back, and the normal helper just treats everything like plain text.
natewill
commented
Apr 2, 2026
| const out = new Map<string, string>() | ||
| const dec = new TextDecoder() | ||
| let i = 0 | ||
| for (const ref of refs) { |
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Each batch entry is either "<ref> missing" for added/deleted files or "<id> blob <byte_size>\n<file_contents>\n".
kitlangton
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Apr 4, 2026
Derived from #20731. Co-authored-by: Nate Williams <50088025+natewill@users.noreply.github.com>
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Issue for this PR
Closes #20734
Closes #11486
Type of change
What does this PR do?
This PR speeds up the
Snapshot.diffFullfunction, somewhat similar to how #20564 and #20551 speed uprevert.Currently,
diffFullhandles one file at a time when when loading blob contents. This means fornfiles it's spawning2ngit processes forgit show from:andgit show to:. Similar to the old revert function, each git process has significant overhead (10-20ms) per process, making the entire function very slow.This change batches files by using
git cat-file --batchto do all of the work forgit showin one git command. This reduces the work forgit showfrom2nto a constant factor of1, while preserving the existing single-file path as a fallback if the batched operation fails.On my machine, a
Snapshot.diffFullfor a 1000 file diffFull went 13.68s to ~0.34s which is a 40x speed up. This function is ran frequently in the application, making this speedup worthwhile.How did you verify your code works?
bun testtests forSnapshot.diffFull(), including:diffFullscenariosAll of these passed
Screenshots / recordings
Not a UI change
Checklist