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Avoid recomputing the logs bloom filter when reading receipts #1407
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Saves a heap of CPU when doing a fast sync.
shemnon
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May 7, 2019
notlesh
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May 14, 2019
PegaSysEng#1407) Significantly reduces CPU usage during a fast sync.
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PR description
When we read transaction receipts from either our local storage or a ETH
ReceiptsMessageas part of fast sync, read the bloom filter from the message rather than recomputing it from the logs.This significantly reduces the amount of CPU required for a fast sync chain download since we can just read 256bits instead of keccak hashing every log and every topic in those logs to recreate the data. As part of importing the block we check that the block's logs bloom matches the hash from the header so have the same level of confidence the bloom filter is correct.
It also reduces the CPU required when loading receipts back out of the database, though in the future we may migrate the DB to not store the bloom filter and prefer saving space over CPU. This change doesn't make that any more difficult.