John Roesler created KAFKA-13526:
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Summary: IQv2: Consider more generic logic for mapping between
binary and typed queries
Key: KAFKA-13526
URL: https://issues.apache.org/jira/browse/KAFKA-13526
Project: Kafka
Issue Type: Sub-task
Reporter: John Roesler
Right now, typed queries (like KeyQuery) need to be specially handled and
translated to their binary counterparts (like RawKeyQuery). This happens in the
Metered store layers, where the serdes are known. It is necessary because lower
store layers are only able to handle binary data (because they don't know the
serdes).
This situation is not ideal, since the Metered store layers will grow to host
quite a bit of query handling and translation logic, because the relationship
between typed queries and binary counterparts is not obvious, and because we
can only automatically translate known query types. User-supplied queries and
stores will have to work things out using their a-priori knowledge of the
serdes.
One suggestion (from [~mjsax] ) is to come up with some kind of generic "query
mapping" API, which the Metered stores would use to translate back and forth
between typed and raw keys and values. Users would be able to supply their own
mappings along with their custom queries.
Another option would be to have the Metered stores attach the serdes to the
query on the way down and then to the result on the way up. Then, the serdes
would be available in the bytes store (as part of the request) and to the users
when they get their results (as part of the response).
Other options may also surface once we start playing with ideas.
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