# Ordered Dict in Base: Is LittleDict not thread safe, and possibly the reason I can't add it to Base?

**URL:** <https://discourse.julialang.org/t/ordered-dict-in-base-is-littledict-not-thread-safe-and-possibly-the-reason-i-cant-add-it-to-base/47372>\
**Category:** General Usage\
**Created:** [September 27, 2020, 8:33pm UTC](https://discourse.julialang.org/t/ordered-dict-in-base-is-littledict-not-thread-safe-and-possibly-the-reason-i-cant-add-it-to-base/47372 "2020-09-27T20:33:32Z")\
**Posts on this page:** 1\
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**Author:** ![simeonschaub](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/simeonschaub/32/216566_2.png) [@simeonschaub](https://discourse.julialang.org/u/simeonschaub)\
**Post date:** [September 28, 2020, 7:22am UTC](https://discourse.julialang.org/t/ordered-dict-in-base-is-littledict-not-thread-safe-and-possibly-the-reason-i-cant-add-it-to-base/47372/4 "2020-09-28T07:22:46Z")

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Also note that `LittleDict` has O(n) lookup cost compared to O(1) for the current `Dict` implementation. This means hat if the collection isn’t super small, `LittleDict` will perform much, much worse than the current implementation. For dicts that are small, Base already has `ImmutableDict`, which has similar performance characteristics for lookup as `LittleDict`, so places where you would really see a benefit of using `LittleDict` should already be using `ImmutableDict` instead of `Dict`.

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_[View the full topic](https://discourse.julialang.org/t/ordered-dict-in-base-is-littledict-not-thread-safe-and-possibly-the-reason-i-cant-add-it-to-base/47372)._