v6: quantizer settings use snake_case names the server never reads

Summary

The quantizer records use snake_case JSON names the server never reads. Weaviate parses these settings out of the config map by exact key, so everything except enabled, bits, segments, centroids and cache is silently dropped on write and null on read — on every index type, not just one. A user who sets a rescore limit never set one.

The mismatch

The server reads them like this — a plain map lookup, no case folding, no snake_case fallback:

// entities/vectorindex/hnsw/rq_config.go
if err := common.OptionalIntFromMap(rqConfigMap, "rescoreLimit", func(v int) {

and returns them under the same names:

type RQConfig struct {
    Enabled      bool  `json:"enabled"`
    Bits         int16 `json:"bits"`
    RescoreLimit int   `json:"rescoreLimit"`
}

So the break is symmetric: what the client sends is ignored, and what the server returns does not bind to the client's fields.

Affected fields

src/main/java/io/weaviate/client6/v1/api/collections/quantizers/:

• RQ.rescoreLimit, BQ.rescoreLimit, SQ.rescoreLimit
• SQ.trainingLimit, PQ.trainingLimit
• PQ.bitCompression
• PQ.encoderType, PQ.encoderDistribution — these are flat components in Java but a nested encoder object on the server, so they need a shape change rather than just a rename

enabled, bits, segments, centroids and cache already match and are unaffected.

Suggested fix

Rename the annotations to the camelCase keys, and give PQ's encoder its nested shape. No alternate values are needed: the snake_case spellings were never valid on the wire, so no stored config uses them.

Version

• java-client 6.3.1 (present since the quantizer records were introduced)
• Weaviate 1.39.0

Found while investigating #606, which is unfixable in practice without this: locating a nested rq still yields a null rescoreLimit.

Start in src/main/java/io/weaviate/client6/v1/api/collections/quantizers/ and inspect the RQ, BQ, SQ, and PQ records against the server sources listed in the issue. Verify serialization and deserialization for camelCase keys and PQ's nested encoder shape; done means all affected settings round-trip using the server's exact names.