* refactor: make Reranker stateless with std::variant value semantics (#461)
Replace class hierarchy (Reranker/ScoreBasedReranker/RrfReranker/
WeightedReranker/CallbackReranker) with std::variant<RrfParams,
WeightedParams, CallbackParams> value type and a stateless free function
reranker::rerank().
Key changes:
- reranker.h: define RerankParams variant + reranker::rerank() API
- query.h: MultiQuery::reranker (shared_ptr) -> MultiQuery::rerank (value)
- schema.h: add CollectionSchema::get_field_ptr() returning FieldSchema::Ptr
- collection.cc: push field lookup to caller, pass vector<FieldSchema::Ptr>
- c_api: remove opaque zvec_reranker_t, add zvec_multi_query_set_rerank_*
- python binding: expose _RrfParams/_WeightedParams/_CallbackParams + setters
- python layer: WeightedReRanker(list[float]), remove Python rerank logic
- all tests updated to new interface
Benefits:
- Thread-safe by design: no mutable state, safe to share across threads
- Collection-decoupled: no bind_schema(), field info passed as parameter
- Simpler lifecycle: value semantics, no shared_ptr management
Closes#461
* chore: remove nightly_build.yml unrelated to reranker refactor
* chore: remove uv.lock unrelated to reranker refactor
* fix: raise ValueError when multi-query has no reranker
After the reranker stateless refactor the C++ MultiQuery rerank
strategy uses a std::variant with a default value, so the implicit
'reranker required' validation no longer triggered. Restore the
check in QueryExecutor._execute_multi_query so that a hybrid
(multi-query) request without a reranker raises ValueError.
* fix(reranker): use index_type FTS check for non-vector normalization
Replace dynamic_cast nullptr check with explicit IndexType::FTS check
and map FTS/BM25 positive scores to (0.0, 1.0) via 2*atan(score)/pi.
* refactor(reranker): move Params types into reranker namespace and qualify usages
Move RrfParams, WeightedParams, CallbackParams and RerankParams into the
zvec::reranker namespace, and add explicit reranker:: qualification at all
usage sites outside the reranker module (query.h, python/c bindings, tests).
* refactor(query): drop unused PendingQuery wrapper, use std::vector<SearchQuery> directly
* refactor(reranker): make _to_cpp_params non-abstract with default NotImplementedError
Remove @abstractmethod from RerankFunction._to_cpp_params and provide a
default implementation raising NotImplementedError. Drop the redundant
_to_cpp_params overrides from Qwen and Sentence rerankers since they use
the Python rerank path and don't need the C++ conversion.
0923f7c691