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Fix hashing algorithm in the firestore spec #1373

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Mar 8, 2021
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Fix hashing algorithm in the firestore spec #1373

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13 changes: 9 additions & 4 deletions docs/specs/online_store_format.md
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Expand Up @@ -74,10 +74,15 @@ We use the following structure to store feature data in the Firestore:

Document id for the feature document is computed by hashing entity key using murmurhash3_128 algorithm as follows:

1. hash utf8-encoded entity names, sorted in alphanumeric order
2. hash the entity values in the same order as corresponding entity names, by serializing them to bytes as follows:
- binary values are hashed as-is
- string values hashed after serializing them as utf8 string
1. hash entity names, sorted in alphanumeric order, by serializing them to bytes using the Value Serialization steps below
2. hash the entity values in the same order as corresponding entity names, by serializing them to bytes using the Value Serialization steps below

Value Serialization:
* Store the type of the value (ValueType enum) as little-endian uint32.
* Store the byte length of the serialized value as little-endian uint32
* Store the serialized value as bytes:
- binary values are serialized as is
- string values serialized as utf8 string
- int64 and int32 hashed as little-endian byte representation (8 and 4 bytes respectively)
- bool hashed as 0 or 1 byte

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