core: remove cached hash code for ItemId #1696
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The id is generated from a hash function, typically SHA1 so we can just use a part of that for the hash code of the id object. Since data is sometimes partitioned and routed based on the most and least significant bits, we pick one of the middle bytes to reduce the liklihood of collisions. Benchmarks show it is about 25% slower to access the hash code this way, but it does provide some memory savings and compute savings when creating an id instance since the murmur hash doesn't need to be computed.
mpalriwal-Netflix
approved these changes
Sep 27, 2024
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The id is generated from a hash function, typically SHA1 so we can just use a part of that for the hash code of the id object. Since data is sometimes partitioned and routed based on the most and least significant bits, we pick one of the middle bytes to reduce the liklihood of collisions.
Benchmarks show it is about 25% slower to access the hash code this way, but it does provide some memory savings and compute savings when creating an id instance since the murmur hash doesn't need to be computed.