enhance: Support hybrid search multiple vector fields (#663)

See also: milvus-io/milvus#25639
milvus pr:  milvus-io/milvus#29433

---------

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>

client/ann_request.go

@@ -0,0 +1,73 @@
+package client
+
+import (
+	"encoding/json"
+	"fmt"
+	"strconv"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+	"github.com/milvus-io/milvus-proto/go-api/v2/milvuspb"
+	"github.com/milvus-io/milvus-sdk-go/v2/entity"
+)
+
+type ANNSearchRequest struct {
+	fieldName   string
+	vectors     []entity.Vector
+	metricType  entity.MetricType
+	expr        string
+	searchParam entity.SearchParam
+	options     []SearchQueryOptionFunc
+	limit       int
+}
+
+func NewANNSearchRequest(fieldName string, metricsType entity.MetricType, vectors []entity.Vector, searchParam entity.SearchParam, limit int, options ...SearchQueryOptionFunc) *ANNSearchRequest {
+	return &ANNSearchRequest{
+		fieldName:   fieldName,
+		vectors:     vectors,
+		metricType:  metricsType,
+		searchParam: searchParam,
+		limit:       limit,
+		options:     options,
+	}
+}
+func (r *ANNSearchRequest) WithExpr(expr string) *ANNSearchRequest {
+	r.expr = expr
+	return r
+}
+
+func (r *ANNSearchRequest) getMilvusSearchRequest(collectionInfo *collInfo) (*milvuspb.SearchRequest, error) {
+	opt := &SearchQueryOption{
+		ConsistencyLevel: collectionInfo.ConsistencyLevel, // default
+	}
+	for _, o := range r.options {
+		o(opt)
+	}
+	params := r.searchParam.Params()
+	params[forTuningKey] = opt.ForTuning
+	bs, err := json.Marshal(params)
+	if err != nil {
+		return nil, err
+	}
+
+	searchParams := entity.MapKvPairs(map[string]string{
+		"anns_field":     r.fieldName,
+		"topk":           fmt.Sprintf("%d", r.limit),
+		"params":         string(bs),
+		"metric_type":    string(r.metricType),
+		"round_decimal":  "-1",
+		ignoreGrowingKey: strconv.FormatBool(opt.IgnoreGrowing),
+		offsetKey:        fmt.Sprintf("%d", opt.Offset),
+		groupByKey:       opt.GroupByField,
+	})
+
+	result := &milvuspb.SearchRequest{
+		DbName:             "",
+		Dsl:                r.expr,
+		PlaceholderGroup:   vector2PlaceholderGroupBytes(r.vectors),
+		DslType:            commonpb.DslType_BoolExprV1,
+		SearchParams:       searchParams,
+		GuaranteeTimestamp: opt.GuaranteeTimestamp,
+		Nq:                 int64(len(r.vectors)),
+	}
+	return result, nil
+}

client/client.go

@@ -219,6 +219,8 @@ type Client interface {
 		msgsBytes [][]byte, startPositions, endPositions []*msgpb.MsgPosition,
 		opts ...ReplicateMessageOption,
 	) (*entity.MessageInfo, error)
+
+	HybridSearch(ctx context.Context, collName string, partitions []string, limit int, outputFields []string, reranker Reranker, subRequests []*ANNSearchRequest) ([]SearchResult, error)
 }
 
 // NewClient create a client connected to remote milvus cluster.

client/client_test.go

@@ -150,6 +150,7 @@ func TestGrpcClientNil(t *testing.T) {
 			if m.Name == "Close" || m.Name == "Connect" || // skip connect & close
 				m.Name == "UsingDatabase" || // skip use database
 				m.Name == "Search" || // type alias MetricType treated as string
+				m.Name == "HybridSearch" || // type alias MetricType treated as string
 				m.Name == "CalcDistance" ||
 				m.Name == "ManualCompaction" || // time.Duration hard to detect in reflect
 				m.Name == "Insert" || m.Name == "Upsert" { // complex methods with ...

client/data.go

@@ -25,6 +25,7 @@ import (
 	"github.com/milvus-io/milvus-proto/go-api/v2/milvuspb"
 	"github.com/milvus-io/milvus-proto/go-api/v2/schemapb"
 	"github.com/milvus-io/milvus-sdk-go/v2/entity"
+	"github.com/milvus-io/milvus-sdk-go/v2/merr"
 )
 
 const (
@@ -35,6 +36,59 @@ const (
 	groupByKey       = `group_by_field`
 )
 
+func (c *GrpcClient) HybridSearch(ctx context.Context, collName string, partitions []string, limit int, outputFields []string, reranker Reranker, subRequests []*ANNSearchRequest) ([]SearchResult, error) {
+	if c.Service == nil {
+		return nil, ErrClientNotReady
+	}
+
+	var schema *entity.Schema
+	collInfo, ok := MetaCache.getCollectionInfo(collName)
+	if !ok {
+		coll, err := c.DescribeCollection(ctx, collName)
+		if err != nil {
+			return nil, err
+		}
+		schema = coll.Schema
+	} else {
+		schema = collInfo.Schema
+	}
+
+	sReqs := make([]*milvuspb.SearchRequest, 0, len(subRequests))
+	nq := 0
+	for _, subRequest := range subRequests {
+		r, err := subRequest.getMilvusSearchRequest(collInfo)
+		if err != nil {
+			return nil, err
+		}
+		r.CollectionName = collName
+		r.PartitionNames = partitions
+		r.OutputFields = outputFields
+		nq = len(subRequest.vectors)
+		sReqs = append(sReqs, r)
+	}
+
+	params := reranker.GetParams()
+	params = append(params, &commonpb.KeyValuePair{Key: limitKey, Value: strconv.FormatInt(int64(limit), 10)})
+
+	req := &milvuspb.HybridSearchRequest{
+		CollectionName:   collName,
+		PartitionNames:   partitions,
+		Requests:         sReqs,
+		OutputFields:     outputFields,
+		ConsistencyLevel: commonpb.ConsistencyLevel(collInfo.ConsistencyLevel),
+		RankParams:       params,
+	}
+
+	result, err := c.Service.HybridSearch(ctx, req)
+
+	err = merr.CheckRPCCall(result, err)
+	if err != nil {
+		return nil, err
+	}
+
+	return c.handleSearchResult(schema, outputFields, nq, result)
+}
+
 // Search with bool expression
 func (c *GrpcClient) Search(ctx context.Context, collName string, partitions []string,
 	expr string, outputFields []string, vectors []entity.Vector, vectorField string, metricType entity.MetricType, topK int, sp entity.SearchParam, opts ...SearchQueryOptionFunc) ([]SearchResult, error) {
@@ -63,7 +117,6 @@ func (c *GrpcClient) Search(ctx context.Context, collName string, partitions []s
 		return nil, err
 	}
 
-	sr := make([]SearchResult, 0, len(vectors))
 	resp, err := c.Service.Search(ctx, req)
 	if err != nil {
 		return nil, err
@@ -72,6 +125,13 @@ func (c *GrpcClient) Search(ctx context.Context, collName string, partitions []s
 		return nil, err
 	}
 	// 3. parse result into result
+	return c.handleSearchResult(schema, outputFields, len(vectors), resp)
+}
+
+func (c *GrpcClient) handleSearchResult(schema *entity.Schema, outputFields []string, nq int, resp *milvuspb.SearchResults) ([]SearchResult, error) {
+	var err error
+	sr := make([]SearchResult, 0, nq)
+	// 3. parse result into result
 	results := resp.GetResults()
 	offset := 0
 	fieldDataList := results.GetFieldsData()

client/reranker.go

@@ -0,0 +1,62 @@
+package client
+
+import (
+	"encoding/json"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+)
+
+const (
+	rerankType    = "strategy"
+	rerankParams  = "params"
+	rffParam      = "k"
+	weightedParam = "weights"
+
+	rrfRerankType      = `rrf`
+	weightedRerankType = `weighted`
+)
+
+type Reranker interface {
+	GetParams() []*commonpb.KeyValuePair
+}
+
+type rrfReranker struct {
+	K float64 `json:"k,omitempty"`
+}
+
+func (r *rrfReranker) WithK(k float64) *rrfReranker {
+	r.K = k
+	return r
+}
+
+func (r *rrfReranker) GetParams() []*commonpb.KeyValuePair {
+	bs, _ := json.Marshal(r)
+
+	return []*commonpb.KeyValuePair{
+		{Key: rerankType, Value: rrfRerankType},
+		{Key: rerankParams, Value: string(bs)},
+	}
+}
+
+func NewRRFReranker() *rrfReranker {
+	return &rrfReranker{K: 60}
+}
+
+type weightedReranker struct {
+	Weights []float64 `json:"weights,omitempty"`
+}
+
+func (r *weightedReranker) GetParams() []*commonpb.KeyValuePair {
+	bs, _ := json.Marshal(r)
+
+	return []*commonpb.KeyValuePair{
+		{Key: rerankType, Value: rrfRerankType},
+		{Key: rerankParams, Value: string(bs)},
+	}
+}
+
+func NewWeightedReranker(weights []float64) *weightedReranker {
+	return &weightedReranker{
+		Weights: weights,
+	}
+}