Add merge() method to ApproxMostFrequentStreamSummary as an optimization over mergeSerialized() #12236
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…ion over mergeSerialized() (facebookincubator#12236) Summary: # Context This diff adds a merge() method which behaves equivalent to mergeSerialized(). The reason this is added is because this avoids the extra round trip serialization + deserialization that's required when calling mergeSerialized(). # Rationale The rationale here is that, the serialize function simply calls values()[i] and priorities()[i], and `memcpy`'s the integers. Then when we deserialize, we also simply take the values as-is and re-insert them into the target data structure. So obviously; rather than ser + deser to perform the exact same operation, we can just copy directly. There are a couple of considerations: 1. **StringView** - Because we do not serialize, velox::StringView is still pointing at whatever `other` ApproxMostFrequentStreamSummary is pointing to, which means *the lifetime of the string must be kept alive across both structures, even if the `other` one disappears*. This ... feels okay, but requires consideration from the user of this class. 2. **StringView equality** - seems like previous behavior is correct (insert will lookup index in priority queue and use operator== on StringView which should compare contents). So technically if all `StringView` point to equal strings, then this won't be problem. Differential Revision: D68995835
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…ion over mergeSerialized() (facebookincubator#12236) Summary: # Context This diff adds a merge() method which behaves equivalent to mergeSerialized(). The reason this is added is because this avoids the extra round trip serialization + deserialization that's required when calling mergeSerialized(). # Rationale The rationale here is that, the serialize function simply calls values()[i] and priorities()[i], and `memcpy`'s the integers. Then when we deserialize, we also simply take the values as-is and re-insert them into the target data structure. So obviously; rather than ser + deser to perform the exact same operation, we can just copy directly. There are a couple of considerations: 1. **StringView** - Because we do not serialize, velox::StringView is still pointing at whatever `other` ApproxMostFrequentStreamSummary is pointing to, which means *the lifetime of the string must be kept alive across both structures, even if the `other` one disappears*. This ... feels okay, but requires consideration from the user of this class. 2. **StringView equality** - seems like previous behavior is correct (insert will lookup index in priority queue and use operator== on StringView which should compare contents). So technically if all `StringView` point to equal strings, then this won't be problem. Reviewed By: Yuhta Differential Revision: D68995835
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Summary:
Context
This diff adds a merge() method which behaves equivalent to mergeSerialized().
The reason this is added is because this avoids the extra round trip serialization + deserialization that's required when calling mergeSerialized().
Rationale
The rationale here is that, the serialize function simply calls values()[i] and priorities()[i], and
memcpy's the integers.Then when we deserialize, we also simply take the values as-is and re-insert them into the target data structure.
So obviously; rather than ser + deser to perform the exact same operation, we can just copy directly.
There are a couple of considerations:
otherApproxMostFrequentStreamSummary is pointing to, which means the lifetime of the string must be kept alive across both structures, even if theotherone disappears. This ... feels okay, but requires consideration from the user of this class.StringViewpoint to equal strings, then this won't be problem.Differential Revision: D68995835