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Type:
Bug
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Resolution: Done
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Priority:
Major - P3
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None
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Affects Version/s: None
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Component/s: None
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Labels:None
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ALL
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Service Arch 2022-06-27, Service Arch 2022-07-11, Service Arch 2022-07-25
One can make the case a flat data structure should be declared with all elements already sorted so run-time checks for elements being contained within the list can be optimized. C++20 has isSorted as a constexpr which therefore can be used with static_asserts possibly failing compilation. This is a betterment to writing a comment above the data structure and hoping for the best as non-sorted lists with silently degrade performance or require extra run-time checks or complicated constructs. Here is a proposal for a possible polyfill:
template <typename It>
constexpr bool constexprIsSorted(It b, It e) {
#if __cpp_lib_constexpr_algorithms >= 201806L
return std::is_sorted(b, e);
#else
if (b == e)
return true;
auto p = b++;
while (b != e) {
if (!(*p < *b))
return false;
p = b++;
}
return true;
#endif
}
And here's an example on how to use it:
// Keep this sorted. constexpr std::array roCmds{ "collStats"_sd, "count"_sd, "dataSize"_sd, "dbStats"_sd, "distinct"_sd, "filemd5"_sd, "find"_sd, "listCollections"_sd, "listIndexes"_sd, "planCacheListFilters"_sd, }; static_assert(constexprIsSorted(roCmds.begin(), roCmds.end())); bool isReadOnlyCommand(StringData cmd) { return std::binary_search(roCmds.begin(), roCmds.end(), cmd); }
- is depended on by
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- Closed
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