Make InternalKeyComparator final and directly use it in merging iterator #2860
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Summary: Merging iterator invokes InternalKeyComparator.Compare() frequently to heap merge. By making InternalKeyComparator final and merging iterator to directly use InternalKeyComparator rather than through Iterator interface, we can give compiler a choice to avoid one more virtual function call if possible. I ran readseq benchmark in memory-only use case to make sure the performance at least doesn't regress. I have to disable the final key word in debug build, as a hack test class depends on overriding the class. Test Plan:run all existing tests
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@siying has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator. |
yiwu-arbug
approved these changes
Sep 11, 2017
| @@ -136,7 +136,11 @@ inline ValueType ExtractValueType(const Slice& internal_key) { | |||
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| // A comparator for internal keys that uses a specified comparator for | |||
| // the user key portion and breaks ties by decreasing sequence number. | |||
| class InternalKeyComparator : public Comparator { | |||
| class InternalKeyComparator | |||
| #ifdef NDEBUG | |||
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Define a macro for this pattern?
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I prefer doing this generalization the second or third time we do it, not the first time. Does it feel OK to you?
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@siying has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator. |
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Summary:
Merging iterator invokes InternalKeyComparator.Compare() frequently to heap merge. By making InternalKeyComparator final and merging iterator to directly use InternalKeyComparator rather than through Iterator interface, we can give compiler a choice to avoid one more virtual function call if possible. I ran readseq benchmark in memory-only use case to make sure the performance at least doesn't regress.
I have to disable the final key word in debug build, as a hack test class depends on overriding the class.
Test Plan:run all existing tests