perf: track deepClone circular refs with a WeakMap#4734
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@lukecotter This does change the behavior though right? It changes it from using |
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@rathboma oof I forgot to add to the map. It’s in my local copy I will sort asap. Sorry about that. |
Replace the O(n) array scan (findIndex per visited object) with an O(1) WeakMap keyed by each source object -> its clone. On large graphs this is ~38x faster at 5k nodes and ~147x at 20k (O(n^2) -> O(n)), matching the reported >5min -> <3s on very large circular graphs. Also fixes a latent correctness bug: the previous list never recorded the root object, so a reference back to the root was cloned as a duplicate object instead of resolving to the same clone. Keying every source object (including the root) preserves shared and circular reference identity. Adds Helpers.deepClone unit tests (deep copy, mutation isolation, shared refs, nested and root circular references).
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Part of #4917 (overview + combined numbers). |
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What
Track circular references in
Helpers.deepClonewith aWeakMap(O(1)) instead of an array scanned per object (O(n)). Record each source object → its clone at entry, and look it up before recursing.Behaviour
Unchanged for normal clones. Also fixes two circular-reference bugs: the array version never recorded the root (a ref back to the root was cloned as a duplicate), and an earlier draft keyed the map by the parent but looked up the child. New
Helpers.spec.jstests cover shared + nested + root circular references. Full suite green.Performance (isolated, Node,
deepCloneof a wide graph)O(n²) → O(n).
Grid impact
Negligible —
deepCloneruns off the render path (Accessor/Localize), and grid rows are small/non-circular (accessorgetDataover 20k rows moved ~7%). The large win is for big/deep/circular data structures. Baselineupstream/master@9539446.