feat: [2.6] Support search with highlighter (#46052)

relate: https://github.com/milvus-io/milvus/issues/42589
pr: https://github.com/milvus-io/milvus/pull/45736
https://github.com/milvus-io/milvus/pull/45099
https://github.com/milvus-io/milvus/pull/44923
https://github.com/milvus-io/milvus/pull/45984

---------

Signed-off-by: aoiasd <zhicheng.yue@zilliz.com>

go.mod

@@ -21,7 +21,7 @@ require (
 	github.com/grpc-ecosystem/go-grpc-middleware v1.3.0
 	github.com/klauspost/compress v1.18.0
 	github.com/mgutz/ansi v0.0.0-20200706080929-d51e80ef957d
-	github.com/milvus-io/milvus-proto/go-api/v2 v2.6.7
+	github.com/milvus-io/milvus-proto/go-api/v2 v2.6.8-0.20251203092105-e2557263fc4c
 	github.com/minio/minio-go/v7 v7.0.73
 	github.com/panjf2000/ants/v2 v2.11.3 // indirect
 	github.com/pingcap/log v1.1.1-0.20221015072633-39906604fb81 // indirect

go.sum

@@ -799,8 +799,8 @@ github.com/milvus-io/cgosymbolizer v0.0.0-20250318084424-114f4050c3a6 h1:YHMFI6L
 github.com/milvus-io/cgosymbolizer v0.0.0-20250318084424-114f4050c3a6/go.mod h1:DvXTE/K/RtHehxU8/GtDs4vFtfw64jJ3PaCnFri8CRg=
 github.com/milvus-io/gorocksdb v0.0.0-20220624081344-8c5f4212846b h1:TfeY0NxYxZzUfIfYe5qYDBzt4ZYRqzUjTR6CvUzjat8=
 github.com/milvus-io/gorocksdb v0.0.0-20220624081344-8c5f4212846b/go.mod h1:iwW+9cWfIzzDseEBCCeDSN5SD16Tidvy8cwQ7ZY8Qj4=
-github.com/milvus-io/milvus-proto/go-api/v2 v2.6.7 h1:RJtZbkS5zKNIXxsqjGBUZc2SbnI4MGq+TfOfc8tJsuM=
+github.com/milvus-io/milvus-proto/go-api/v2 v2.6.8-0.20251203092105-e2557263fc4c h1:Gh02wIJEI6RUbEXwZworPBfK9BYd1SVBIDHDL8GsrCY=
-github.com/milvus-io/milvus-proto/go-api/v2 v2.6.7/go.mod h1:/6UT4zZl6awVeXLeE7UGDWZvXj3IWkRsh3mqsn0DiAs=
+github.com/milvus-io/milvus-proto/go-api/v2 v2.6.8-0.20251203092105-e2557263fc4c/go.mod h1:/6UT4zZl6awVeXLeE7UGDWZvXj3IWkRsh3mqsn0DiAs=
 github.com/minio/asm2plan9s v0.0.0-20200509001527-cdd76441f9d8 h1:AMFGa4R4MiIpspGNG7Z948v4n35fFGB3RR3G/ry4FWs=
 github.com/minio/asm2plan9s v0.0.0-20200509001527-cdd76441f9d8/go.mod h1:mC1jAcsrzbxHt8iiaC+zU4b1ylILSosueou12R++wfY=
 github.com/minio/c2goasm v0.0.0-20190812172519-36a3d3bbc4f3 h1:+n/aFZefKZp7spd8DFdX7uMikMLXX4oubIzJF4kv/wI=

internal/distributed/querynode/client/client.go

@@ -394,3 +394,14 @@ func (c *Client) DropIndex(ctx context.Context, req *querypb.DropIndexRequest, _
 		return client.DropIndex(ctx, req)
 	})
 }
+
+func (c *Client) GetHighlight(ctx context.Context, req *querypb.GetHighlightRequest, _ ...grpc.CallOption) (*querypb.GetHighlightResponse, error) {
+	req = typeutil.Clone(req)
+	commonpbutil.UpdateMsgBase(
+		req.GetBase(),
+		commonpbutil.FillMsgBaseFromClient(c.nodeID),
+	)
+	return wrapGrpcCall(ctx, c, func(client querypb.QueryNodeClient) (*querypb.GetHighlightResponse, error) {
+		return client.GetHighlight(ctx, req)
+	})
+}

internal/distributed/querynode/client/client_test.go

@@ -111,6 +111,12 @@ func Test_NewClient(t *testing.T) {
 		r21, err := client.DeleteBatch(ctx, nil)
 		retCheck(retNotNil, r21, err)
 
+		r22, err := client.RunAnalyzer(ctx, nil)
+		retCheck(retNotNil, r22, err)
+
+		r24, err := client.GetHighlight(ctx, nil)
+		retCheck(retNotNil, r24, err)
+
 		// stream rpc
 		client, err := client.QueryStream(ctx, nil)
 		retCheck(retNotNil, client, err)

internal/distributed/querynode/service.go

@@ -407,3 +407,7 @@ func (s *Server) RunAnalyzer(ctx context.Context, req *querypb.RunAnalyzerReques
 func (s *Server) DropIndex(ctx context.Context, req *querypb.DropIndexRequest) (*commonpb.Status, error) {
 	return s.querynode.DropIndex(ctx, req)
 }
+
+func (s *Server) GetHighlight(ctx context.Context, req *querypb.GetHighlightRequest) (*querypb.GetHighlightResponse, error) {
+	return s.querynode.GetHighlight(ctx, req)
+}

internal/distributed/querynode/service_test.go

@@ -280,6 +280,28 @@ func Test_NewServer(t *testing.T) {
 		assert.NoError(t, merr.CheckRPCCall(resp, err))
 	})
 
+	t.Run("RunAnalyzer", func(t *testing.T) {
+		mockQN.EXPECT().RunAnalyzer(mock.Anything, mock.Anything).Return(&milvuspb.RunAnalyzerResponse{
+			Status: &commonpb.Status{ErrorCode: commonpb.ErrorCode_Success},
+		}, nil)
+		req := &querypb.RunAnalyzerRequest{}
+		resp, err := server.RunAnalyzer(ctx, req)
+		assert.NoError(t, err)
+		assert.Equal(t, commonpb.ErrorCode_Success, resp.GetStatus().GetErrorCode())
+	})
+
+	t.Run("GetHighlight", func(t *testing.T) {
+		mockQN.EXPECT().GetHighlight(mock.Anything, mock.Anything).Return(&querypb.GetHighlightResponse{
+			Status: merr.Success(),
+		}, nil)
+
+		resp, err := server.GetHighlight(ctx, &querypb.GetHighlightRequest{
+			Channel: "test-channel",
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, commonpb.ErrorCode_Success, resp.GetStatus().GetErrorCode())
+	})
+
 	err = server.Stop()
 	assert.NoError(t, err)
 }

internal/mocks/mock_querynode.go

@@ -370,6 +370,65 @@ func (_c *MockQueryNode_GetDataDistribution_Call) RunAndReturn(run func(context.
 	return _c
 }
 
+// GetHighlight provides a mock function with given fields: _a0, _a1
+func (_m *MockQueryNode) GetHighlight(_a0 context.Context, _a1 *querypb.GetHighlightRequest) (*querypb.GetHighlightResponse, error) {
+	ret := _m.Called(_a0, _a1)
+
+	if len(ret) == 0 {
+		panic("no return value specified for GetHighlight")
+	}
+
+	var r0 *querypb.GetHighlightResponse
+	var r1 error
+	if rf, ok := ret.Get(0).(func(context.Context, *querypb.GetHighlightRequest) (*querypb.GetHighlightResponse, error)); ok {
+		return rf(_a0, _a1)
+	}
+	if rf, ok := ret.Get(0).(func(context.Context, *querypb.GetHighlightRequest) *querypb.GetHighlightResponse); ok {
+		r0 = rf(_a0, _a1)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(*querypb.GetHighlightResponse)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func(context.Context, *querypb.GetHighlightRequest) error); ok {
+		r1 = rf(_a0, _a1)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
+// MockQueryNode_GetHighlight_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'GetHighlight'
+type MockQueryNode_GetHighlight_Call struct {
+	*mock.Call
+}
+
+// GetHighlight is a helper method to define mock.On call
+//   - _a0 context.Context
+//   - _a1 *querypb.GetHighlightRequest
+func (_e *MockQueryNode_Expecter) GetHighlight(_a0 interface{}, _a1 interface{}) *MockQueryNode_GetHighlight_Call {
+	return &MockQueryNode_GetHighlight_Call{Call: _e.mock.On("GetHighlight", _a0, _a1)}
+}
+
+func (_c *MockQueryNode_GetHighlight_Call) Run(run func(_a0 context.Context, _a1 *querypb.GetHighlightRequest)) *MockQueryNode_GetHighlight_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run(args[0].(context.Context), args[1].(*querypb.GetHighlightRequest))
+	})
+	return _c
+}
+
+func (_c *MockQueryNode_GetHighlight_Call) Return(_a0 *querypb.GetHighlightResponse, _a1 error) *MockQueryNode_GetHighlight_Call {
+	_c.Call.Return(_a0, _a1)
+	return _c
+}
+
+func (_c *MockQueryNode_GetHighlight_Call) RunAndReturn(run func(context.Context, *querypb.GetHighlightRequest) (*querypb.GetHighlightResponse, error)) *MockQueryNode_GetHighlight_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
 // GetMetrics provides a mock function with given fields: _a0, _a1
 func (_m *MockQueryNode) GetMetrics(_a0 context.Context, _a1 *milvuspb.GetMetricsRequest) (*milvuspb.GetMetricsResponse, error) {
 	ret := _m.Called(_a0, _a1)

internal/mocks/mock_querynode_client.go

@@ -446,6 +446,80 @@ func (_c *MockQueryNodeClient_GetDataDistribution_Call) RunAndReturn(run func(co
 	return _c
 }
 
+// GetHighlight provides a mock function with given fields: ctx, in, opts
+func (_m *MockQueryNodeClient) GetHighlight(ctx context.Context, in *querypb.GetHighlightRequest, opts ...grpc.CallOption) (*querypb.GetHighlightResponse, error) {
+	_va := make([]interface{}, len(opts))
+	for _i := range opts {
+		_va[_i] = opts[_i]
+	}
+	var _ca []interface{}
+	_ca = append(_ca, ctx, in)
+	_ca = append(_ca, _va...)
+	ret := _m.Called(_ca...)
+
+	if len(ret) == 0 {
+		panic("no return value specified for GetHighlight")
+	}
+
+	var r0 *querypb.GetHighlightResponse
+	var r1 error
+	if rf, ok := ret.Get(0).(func(context.Context, *querypb.GetHighlightRequest, ...grpc.CallOption) (*querypb.GetHighlightResponse, error)); ok {
+		return rf(ctx, in, opts...)
+	}
+	if rf, ok := ret.Get(0).(func(context.Context, *querypb.GetHighlightRequest, ...grpc.CallOption) *querypb.GetHighlightResponse); ok {
+		r0 = rf(ctx, in, opts...)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(*querypb.GetHighlightResponse)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func(context.Context, *querypb.GetHighlightRequest, ...grpc.CallOption) error); ok {
+		r1 = rf(ctx, in, opts...)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
+// MockQueryNodeClient_GetHighlight_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'GetHighlight'
+type MockQueryNodeClient_GetHighlight_Call struct {
+	*mock.Call
+}
+
+// GetHighlight is a helper method to define mock.On call
+//   - ctx context.Context
+//   - in *querypb.GetHighlightRequest
+//   - opts ...grpc.CallOption
+func (_e *MockQueryNodeClient_Expecter) GetHighlight(ctx interface{}, in interface{}, opts ...interface{}) *MockQueryNodeClient_GetHighlight_Call {
+	return &MockQueryNodeClient_GetHighlight_Call{Call: _e.mock.On("GetHighlight",
+		append([]interface{}{ctx, in}, opts...)...)}
+}
+
+func (_c *MockQueryNodeClient_GetHighlight_Call) Run(run func(ctx context.Context, in *querypb.GetHighlightRequest, opts ...grpc.CallOption)) *MockQueryNodeClient_GetHighlight_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		variadicArgs := make([]grpc.CallOption, len(args)-2)
+		for i, a := range args[2:] {
+			if a != nil {
+				variadicArgs[i] = a.(grpc.CallOption)
+			}
+		}
+		run(args[0].(context.Context), args[1].(*querypb.GetHighlightRequest), variadicArgs...)
+	})
+	return _c
+}
+
+func (_c *MockQueryNodeClient_GetHighlight_Call) Return(_a0 *querypb.GetHighlightResponse, _a1 error) *MockQueryNodeClient_GetHighlight_Call {
+	_c.Call.Return(_a0, _a1)
+	return _c
+}
+
+func (_c *MockQueryNodeClient_GetHighlight_Call) RunAndReturn(run func(context.Context, *querypb.GetHighlightRequest, ...grpc.CallOption) (*querypb.GetHighlightResponse, error)) *MockQueryNodeClient_GetHighlight_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
 // GetMetrics provides a mock function with given fields: ctx, in, opts
 func (_m *MockQueryNodeClient) GetMetrics(ctx context.Context, in *milvuspb.GetMetricsRequest, opts ...grpc.CallOption) (*milvuspb.GetMetricsResponse, error) {
 	_va := make([]interface{}, len(opts))

internal/proxy/highlighter.go

@@ -0,0 +1,403 @@
+package proxy
+
+import (
+	"context"
+	"encoding/json"
+	"strconv"
+	"strings"
+
+	"github.com/cockroachdb/errors"
+	"github.com/samber/lo"
+	"go.opentelemetry.io/otel/trace"
+
+	"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-proto/go-api/v2/schemapb"
+	"github.com/milvus-io/milvus/internal/proxy/shardclient"
+	"github.com/milvus-io/milvus/pkg/v2/proto/querypb"
+	"github.com/milvus-io/milvus/pkg/v2/util/funcutil"
+	"github.com/milvus-io/milvus/pkg/v2/util/merr"
+	"github.com/milvus-io/milvus/pkg/v2/util/typeutil"
+)
+
+const (
+	PreTagsKey             = "pre_tags"
+	PostTagsKey            = "post_tags"
+	HighlightSearchTextKey = "highlight_search_text"
+	HighlightQueryKey      = "queries"
+	FragmentOffsetKey      = "fragment_offset"
+	FragmentSizeKey        = "fragment_size"
+	FragmentNumKey         = "num_of_fragments"
+	DefaultFragmentSize    = 100
+	DefaultFragmentNum     = 5
+	DefaultPreTag          = "<em>"
+	DefaultPostTag         = "</em>"
+)
+
+type Highlighter interface {
+	AsSearchPipelineOperator(t *searchTask) (operator, error)
+	FieldIDs() []int64
+}
+
+// highlight task for one field
+type highlightTask struct {
+	*querypb.HighlightTask
+	preTags  [][]byte
+	postTags [][]byte
+}
+
+type highlightQuery struct {
+	text          string
+	fieldName     string
+	highlightType querypb.HighlightQueryType
+}
+
+type LexicalHighlighter struct {
+	tasks map[int64]*highlightTask // fieldID -> highlightTask
+	// option for all highlight task
+	// TODO: support set option for each task
+	preTags         [][]byte
+	postTags        [][]byte
+	highlightSearch bool
+	options         *querypb.HighlightOptions
+	queries         []*highlightQuery
+}
+
+// add highlight task with search
+// must used before addTaskWithQuery
+func (h *LexicalHighlighter) addTaskWithSearchText(fieldID int64, fieldName string, analyzerName string, texts []string) error {
+	_, ok := h.tasks[fieldID]
+	if ok {
+		return merr.WrapErrParameterInvalidMsg("not support hybrid search with highlight now. fieldID: %d", fieldID)
+	}
+
+	task := &highlightTask{
+		preTags:  h.preTags,
+		postTags: h.postTags,
+		HighlightTask: &querypb.HighlightTask{
+			FieldName: fieldName,
+			FieldId:   fieldID,
+			Options:   h.options,
+		},
+	}
+	h.tasks[fieldID] = task
+
+	task.Texts = texts
+	task.SearchTextNum = int64(len(texts))
+	if analyzerName != "" {
+		task.AnalyzerNames = []string{}
+		for i := 0; i < len(texts); i++ {
+			task.AnalyzerNames = append(task.AnalyzerNames, analyzerName)
+		}
+	}
+	return nil
+}
+
+func (h *LexicalHighlighter) addTaskWithQuery(fieldID int64, query *highlightQuery) {
+	task, ok := h.tasks[fieldID]
+	if !ok {
+		task = &highlightTask{
+			HighlightTask: &querypb.HighlightTask{
+				Texts:     []string{},
+				FieldId:   fieldID,
+				FieldName: query.fieldName,
+				Options:   h.options,
+			},
+			preTags:  h.preTags,
+			postTags: h.postTags,
+		}
+		h.tasks[fieldID] = task
+	}
+
+	task.Texts = append(task.Texts, query.text)
+	task.Queries = append(task.Queries, &querypb.HighlightQuery{
+		Type: query.highlightType,
+	})
+}
+
+func (h *LexicalHighlighter) initHighlightQueries(t *searchTask) error {
+	// add query to highlight tasks
+	for _, query := range h.queries {
+		fieldID, ok := t.schema.MapFieldID(query.fieldName)
+		if !ok {
+			return merr.WrapErrParameterInvalidMsg("highlight field not found in schema: %s", query.fieldName)
+		}
+		h.addTaskWithQuery(fieldID, query)
+	}
+	return nil
+}
+
+func (h *LexicalHighlighter) AsSearchPipelineOperator(t *searchTask) (operator, error) {
+	return newLexicalHighlightOperator(t, lo.Values(h.tasks))
+}
+
+func (h *LexicalHighlighter) FieldIDs() []int64 {
+	return lo.Keys(h.tasks)
+}
+
+func NewLexicalHighlighter(highlighter *commonpb.Highlighter) (*LexicalHighlighter, error) {
+	params := funcutil.KeyValuePair2Map(highlighter.GetParams())
+	h := &LexicalHighlighter{
+		tasks:   make(map[int64]*highlightTask),
+		options: &querypb.HighlightOptions{},
+	}
+
+	// set pre_tags and post_tags
+	if value, ok := params[PreTagsKey]; ok {
+		tags := []string{}
+		if err := json.Unmarshal([]byte(value), &tags); err != nil {
+			return nil, merr.WrapErrParameterInvalidMsg("unmarshal pre_tags as string array failed: %v", err)
+		}
+		if len(tags) == 0 {
+			return nil, merr.WrapErrParameterInvalidMsg("pre_tags cannot be empty list")
+		}
+
+		h.preTags = make([][]byte, len(tags))
+		for i, tag := range tags {
+			h.preTags[i] = []byte(tag)
+		}
+	} else {
+		h.preTags = [][]byte{[]byte(DefaultPreTag)}
+	}
+
+	if value, ok := params[PostTagsKey]; ok {
+		tags := []string{}
+		if err := json.Unmarshal([]byte(value), &tags); err != nil {
+			return nil, merr.WrapErrParameterInvalidMsg("unmarshal post_tags as string list failed: %v", err)
+		}
+		if len(tags) == 0 {
+			return nil, merr.WrapErrParameterInvalidMsg("post_tags cannot be empty list")
+		}
+		h.postTags = make([][]byte, len(tags))
+		for i, tag := range tags {
+			h.postTags[i] = []byte(tag)
+		}
+	} else {
+		h.postTags = [][]byte{[]byte(DefaultPostTag)}
+	}
+
+	// set fragment config
+	if value, ok := params[FragmentSizeKey]; ok {
+		fragmentSize, err := strconv.ParseInt(value, 10, 64)
+		if err != nil || fragmentSize <= 0 {
+			return nil, merr.WrapErrParameterInvalidMsg("invalid fragment_size: %s", value)
+		}
+		h.options.FragmentSize = fragmentSize
+	} else {
+		h.options.FragmentSize = DefaultFragmentSize
+	}
+
+	if value, ok := params[FragmentNumKey]; ok {
+		fragmentNum, err := strconv.ParseInt(value, 10, 64)
+		if err != nil || fragmentNum < 0 {
+			return nil, merr.WrapErrParameterInvalidMsg("invalid num_of_fragments: %s", value)
+		}
+		h.options.NumOfFragments = fragmentNum
+	} else {
+		h.options.NumOfFragments = DefaultFragmentNum
+	}
+
+	if value, ok := params[FragmentOffsetKey]; ok {
+		fragmentOffset, err := strconv.ParseInt(value, 10, 64)
+		if err != nil || fragmentOffset < 0 {
+			return nil, merr.WrapErrParameterInvalidMsg("invalid fragment_offset: %s", value)
+		}
+		h.options.FragmentOffset = fragmentOffset
+	}
+
+	if value, ok := params[HighlightSearchTextKey]; ok {
+		enable, err := strconv.ParseBool(value)
+		if err != nil {
+			return nil, merr.WrapErrParameterInvalidMsg("unmarshal highlight_search_text as bool failed: %v", err)
+		}
+
+		h.highlightSearch = enable
+	}
+
+	if value, ok := params[HighlightQueryKey]; ok {
+		queries := []any{}
+		if err := json.Unmarshal([]byte(value), &queries); err != nil {
+			return nil, merr.WrapErrParameterInvalidMsg("unmarshal highlight queries as json array failed: %v", err)
+		}
+
+		for _, query := range queries {
+			m, ok := query.(map[string]any)
+			if !ok {
+				return nil, merr.WrapErrParameterInvalidMsg("unmarshal highlight queries failed: item in array is not json object")
+			}
+
+			text, ok := m["text"]
+			if !ok {
+				return nil, merr.WrapErrParameterInvalidMsg("unmarshal highlight queries failed: must set `text` in query")
+			}
+
+			textStr, ok := text.(string)
+			if !ok {
+				return nil, merr.WrapErrParameterInvalidMsg("unmarshal highlight queries failed: `text` must be string")
+			}
+
+			t, ok := m["type"]
+			if !ok {
+				return nil, merr.WrapErrParameterInvalidMsg("unmarshal highlight queries failed: must set `type` in query")
+			}
+
+			typeStr, ok := t.(string)
+			if !ok {
+				return nil, merr.WrapErrParameterInvalidMsg("unmarshal highlight queries failed: `type` must be string")
+			}
+
+			typeEnum, ok := querypb.HighlightQueryType_value[typeStr]
+			if !ok {
+				return nil, merr.WrapErrParameterInvalidMsg("unmarshal highlight queries failed: invalid highlight query type: %s", typeStr)
+			}
+
+			f, ok := m["field"]
+			if !ok {
+				return nil, merr.WrapErrParameterInvalidMsg("unmarshal highlight queries failed: must set `field` in query")
+			}
+			fieldStr, ok := f.(string)
+			if !ok {
+				return nil, merr.WrapErrParameterInvalidMsg("unmarshal highlight queries failed: `field` must be string")
+			}
+
+			h.queries = append(h.queries, &highlightQuery{
+				text:          textStr,
+				highlightType: querypb.HighlightQueryType(typeEnum),
+				fieldName:     fieldStr,
+			})
+		}
+	}
+	return h, nil
+}
+
+type lexicalHighlightOperator struct {
+	tasks        []*highlightTask
+	fieldSchemas []*schemapb.FieldSchema
+	lbPolicy     shardclient.LBPolicy
+	scheduler    *taskScheduler
+
+	collectionName string
+	collectionID   int64
+	dbName         string
+}
+
+func newLexicalHighlightOperator(t *searchTask, tasks []*highlightTask) (operator, error) {
+	return &lexicalHighlightOperator{
+		tasks:          tasks,
+		lbPolicy:       t.lb,
+		scheduler:      t.node.(*Proxy).sched,
+		fieldSchemas:   typeutil.GetAllFieldSchemas(t.schema.CollectionSchema),
+		collectionName: t.request.CollectionName,
+		collectionID:   t.CollectionID,
+		dbName:         t.request.DbName,
+	}, nil
+}
+
+func (op *lexicalHighlightOperator) run(ctx context.Context, span trace.Span, inputs ...any) ([]any, error) {
+	result := inputs[0].(*milvuspb.SearchResults)
+	datas := result.Results.GetFieldsData()
+	req := &querypb.GetHighlightRequest{
+		Topks: result.GetResults().GetTopks(),
+		Tasks: lo.Map(op.tasks, func(task *highlightTask, _ int) *querypb.HighlightTask { return task.HighlightTask }),
+	}
+
+	for _, task := range req.GetTasks() {
+		textFieldDatas, ok := lo.Find(datas, func(data *schemapb.FieldData) bool { return data.FieldId == task.GetFieldId() })
+		if !ok {
+			return nil, errors.Errorf("get highlight failed, text field not in output field %s: %d", task.GetFieldName(), task.GetFieldId())
+		}
+		texts := textFieldDatas.GetScalars().GetStringData().GetData()
+		task.Texts = append(task.Texts, texts...)
+		task.CorpusTextNum = int64(len(texts))
+		field, ok := lo.Find(op.fieldSchemas, func(schema *schemapb.FieldSchema) bool {
+			return schema.GetFieldID() == task.GetFieldId()
+		})
+		if !ok {
+			return nil, errors.Errorf("get highlight failed, field not found in schema %s: %d", task.GetFieldName(), task.GetFieldId())
+		}
+
+		// if use multi analyzer
+		// get analyzer field data
+		helper := typeutil.CreateFieldSchemaHelper(field)
+		if v, ok := helper.GetMultiAnalyzerParams(); ok {
+			params := map[string]any{}
+			err := json.Unmarshal([]byte(v), &params)
+			if err != nil {
+				return nil, errors.Errorf("get highlight failed, get invalid multi analyzer params-: %v", err)
+			}
+			analyzerField, ok := params["by_field"]
+			if !ok {
+				return nil, errors.Errorf("get highlight failed, get invalid multi analyzer params, no by_field")
+			}
+
+			analyzerFieldDatas, ok := lo.Find(datas, func(data *schemapb.FieldData) bool { return data.FieldName == analyzerField.(string) })
+			if !ok {
+				return nil, errors.Errorf("get highlight failed, analyzer field not in output field")
+			}
+			task.AnalyzerNames = append(task.AnalyzerNames, analyzerFieldDatas.GetScalars().GetStringData().GetData()...)
+		}
+	}
+
+	task := &HighlightTask{
+		ctx:                 ctx,
+		lb:                  op.lbPolicy,
+		Condition:           NewTaskCondition(ctx),
+		GetHighlightRequest: req,
+		collectionName:      op.collectionName,
+		collectionID:        op.collectionID,
+		dbName:              op.dbName,
+	}
+	if err := op.scheduler.dqQueue.Enqueue(task); err != nil {
+		return nil, err
+	}
+
+	if err := task.WaitToFinish(); err != nil {
+		return nil, err
+	}
+
+	rowNum := len(result.Results.GetScores())
+	HighlightResults := []*commonpb.HighlightResult{}
+	if rowNum != 0 {
+		rowDatas := lo.Map(task.result.Results, func(result *querypb.HighlightResult, i int) *commonpb.HighlightData {
+			return buildStringFragments(op.tasks[i/rowNum], i%rowNum, result.GetFragments())
+		})
+
+		for i, task := range req.GetTasks() {
+			HighlightResults = append(HighlightResults, &commonpb.HighlightResult{
+				FieldName: task.GetFieldName(),
+				Datas:     rowDatas[i*rowNum : (i+1)*rowNum],
+			})
+		}
+	}
+
+	result.Results.HighlightResults = HighlightResults
+	return []any{result}, nil
+}
+
+func buildStringFragments(task *highlightTask, idx int, frags []*querypb.HighlightFragment) *commonpb.HighlightData {
+	startOffset := int(task.GetSearchTextNum()) + len(task.Queries)
+	text := []rune(task.Texts[startOffset+idx])
+	preTagsNum := len(task.preTags)
+	postTagsNum := len(task.postTags)
+	result := &commonpb.HighlightData{Fragments: make([]string, 0)}
+	for _, frag := range frags {
+		var fragString strings.Builder
+		cursor := int(frag.GetStartOffset())
+		for i := 0; i < len(frag.GetOffsets())/2; i++ {
+			startOffset := int(frag.Offsets[i<<1])
+			endOffset := int(frag.Offsets[(i<<1)+1])
+			if cursor < startOffset {
+				fragString.WriteString(string(text[cursor:startOffset]))
+			}
+			fragString.WriteString(string(task.preTags[i%preTagsNum]))
+			fragString.WriteString(string(text[startOffset:endOffset]))
+			fragString.WriteString(string(task.postTags[i%postTagsNum]))
+			cursor = endOffset
+		}
+		if cursor < int(frag.GetEndOffset()) {
+			fragString.WriteString(string(text[cursor:frag.GetEndOffset()]))
+		}
+		result.Fragments = append(result.Fragments, fragString.String())
+	}
+	return result
+}

internal/proxy/search_pipeline.go

@@ -112,6 +112,7 @@ const (
 	organizeOp           = "organize"
 	endOp                = "end"
 	lambdaOp             = "lambda"
+	highlightOp          = "highlight"
 )
 
 const (
@@ -128,6 +129,7 @@ var opFactory = map[string]func(t *searchTask, params map[string]any) (operator,
 	requeryOp:            newRequeryOperator,
 	lambdaOp:             newLambdaOperator,
 	endOp:                newEndOperator,
+	highlightOp:          newHighlightOperator,
 }
 
 func NewNode(info *nodeDef, t *searchTask) (*Node, error) {
@@ -596,6 +598,10 @@ func (op *endOperator) run(ctx context.Context, span trace.Span, inputs ...any)
 	return []any{result}, nil
 }
 
+func newHighlightOperator(t *searchTask, _ map[string]any) (operator, error) {
+	return t.highlighter.AsSearchPipelineOperator(t)
+}
+
 func mergeIDsFunc(ctx context.Context, span trace.Span, inputs ...any) ([]any, error) {
 	multipleMilvusResults := inputs[0].([]*milvuspb.SearchResults)
 	idInt64Type := false
@@ -652,6 +658,17 @@ func newPipeline(pipeDef *pipelineDef, t *searchTask) (*pipeline, error) {
 	return &pipeline{name: pipeDef.name, nodes: nodes}, nil
 }
 
+func (p *pipeline) AddNodes(t *searchTask, nodes ...*nodeDef) error {
+	for _, def := range nodes {
+		node, err := NewNode(def, t)
+		if err != nil {
+			return err
+		}
+		p.nodes = append(p.nodes, node)
+	}
+	return nil
+}
+
 func (p *pipeline) Run(ctx context.Context, span trace.Span, toReduceResults []*internalpb.SearchResults, storageCost segcore.StorageCost) (*milvuspb.SearchResults, segcore.StorageCost, error) {
 	log.Ctx(ctx).Debug("SearchPipeline run", zap.String("pipeline", p.String()))
 	msg := opMsg{}
@@ -682,6 +699,20 @@ type pipelineDef struct {
 	nodes []*nodeDef
 }
 
+var filterFieldNode = &nodeDef{
+	name:    "filter_field",
+	inputs:  []string{"result", "reduced"},
+	outputs: []string{"output"},
+	opName:  endOp,
+}
+
+var highlightNode = &nodeDef{
+	name:    "highlight",
+	inputs:  []string{"result"},
+	outputs: []string{"output"},
+	opName:  highlightOp,
+}
+
 var searchPipe = &pipelineDef{
 	name: "search",
 	nodes: []*nodeDef{
@@ -703,12 +734,6 @@ var searchPipe = &pipelineDef{
 			},
 			opName: lambdaOp,
 		},
-		{
-			name:    "filter_field",
-			inputs:  []string{"result", "reduced"},
-			outputs: []string{pipelineOutput},
-			opName:  endOp,
-		},
 	},
 }
 
@@ -767,12 +792,6 @@ var searchWithRequeryPipe = &pipelineDef{
 			},
 			opName: lambdaOp,
 		},
-		{
-			name:    "filter_field",
-			inputs:  []string{"result", "reduced"},
-			outputs: []string{pipelineOutput},
-			opName:  endOp,
-		},
 	},
 }
 
@@ -825,12 +844,6 @@ var searchWithRerankPipe = &pipelineDef{
 			},
 			opName: lambdaOp,
 		},
-		{
-			name:    "filter_field",
-			inputs:  []string{"result", "reduced"},
-			outputs: []string{pipelineOutput},
-			opName:  endOp,
-		},
 	},
 }
 
@@ -899,12 +912,6 @@ var searchWithRerankRequeryPipe = &pipelineDef{
 			},
 			opName: lambdaOp,
 		},
-		{
-			name:    "filter_field",
-			inputs:  []string{"result", "reduced"},
-			outputs: []string{pipelineOutput},
-			opName:  endOp,
-		},
 	},
 }
 
@@ -923,12 +930,6 @@ var hybridSearchPipe = &pipelineDef{
 			outputs: []string{"result"},
 			opName:  rerankOp,
 		},
-		{
-			name:    "filter_field",
-			inputs:  []string{"result", "reduced"},
-			outputs: []string{pipelineOutput},
-			opName:  endOp,
-		},
 	},
 }
 
@@ -1030,12 +1031,6 @@ var hybridSearchWithRequeryAndRerankByFieldDataPipe = &pipelineDef{
 			},
 			opName: lambdaOp,
 		},
-		{
-			name:    "filter_field",
-			inputs:  []string{"result", "reduced"},
-			outputs: []string{pipelineOutput},
-			opName:  endOp,
-		},
 	},
 }
 
@@ -1093,12 +1088,6 @@ var hybridSearchWithRequeryPipe = &pipelineDef{
 			},
 			opName: lambdaOp,
 		},
-		{
-			name:    "filter_field",
-			inputs:  []string{"result", "reduced"},
-			outputs: []string{pipelineOutput},
-			opName:  endOp,
-		},
 	},
 }
 
@@ -1142,3 +1131,23 @@ func aggregatedAllSearchCount(searchResults []*milvuspb.SearchResults) int64 {
 	}
 	return allSearchCount
 }
+
+func newSearchPipeline(t *searchTask) (*pipeline, error) {
+	p, err := newBuiltInPipeline(t)
+	if err != nil {
+		return nil, err
+	}
+
+	if t.highlighter != nil {
+		err := p.AddNodes(t, highlightNode, filterFieldNode)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		err := p.AddNodes(t, filterFieldNode)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return p, nil
+}

internal/proxy/search_pipeline_test.go

@@ -24,6 +24,7 @@ import (
 	"time"
 
 	"github.com/bytedance/mockey"
+	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/suite"
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/trace"
@@ -31,10 +32,14 @@ import (
 	"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-proto/go-api/v2/schemapb"
+	"github.com/milvus-io/milvus/internal/mocks"
+	"github.com/milvus-io/milvus/internal/proxy/shardclient"
 	"github.com/milvus-io/milvus/internal/util/function/rerank"
 	"github.com/milvus-io/milvus/internal/util/segcore"
 	"github.com/milvus-io/milvus/pkg/v2/proto/internalpb"
 	"github.com/milvus-io/milvus/pkg/v2/proto/planpb"
+	"github.com/milvus-io/milvus/pkg/v2/proto/querypb"
+	"github.com/milvus-io/milvus/pkg/v2/util/merr"
 	"github.com/milvus-io/milvus/pkg/v2/util/testutils"
 	"github.com/milvus-io/milvus/pkg/v2/util/timerecord"
 )
@@ -266,6 +271,96 @@ func (s *SearchPipelineSuite) TestOrganizeOp() {
 	fmt.Println(ret)
 }
 
+func (s *SearchPipelineSuite) TestHighlightOp() {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	proxy := &Proxy{}
+	proxy.tsoAllocator = &timestampAllocator{
+		tso: newMockTimestampAllocatorInterface(),
+	}
+	sched, err := newTaskScheduler(ctx, proxy.tsoAllocator)
+	s.Require().NoError(err)
+
+	err = sched.Start()
+	s.Require().NoError(err)
+	defer sched.Close()
+	proxy.sched = sched
+
+	collName := "test_coll_highlight"
+	fieldName2Types := map[string]schemapb.DataType{
+		testVarCharField: schemapb.DataType_VarChar,
+	}
+	schema := constructCollectionSchemaByDataType(collName, fieldName2Types, testVarCharField, false)
+
+	req := &milvuspb.SearchRequest{
+		CollectionName: collName,
+		DbName:         "default",
+	}
+
+	highlightTasks := map[int64]*highlightTask{
+		100: {
+			HighlightTask: &querypb.HighlightTask{
+				Texts:     []string{"target text"},
+				FieldName: testVarCharField,
+				FieldId:   100,
+			},
+			preTags:  [][]byte{[]byte(DefaultPreTag)},
+			postTags: [][]byte{[]byte(DefaultPostTag)},
+		},
+	}
+
+	mockLb := shardclient.NewMockLBPolicy(s.T())
+	searchTask := &searchTask{
+		node: proxy,
+		highlighter: &LexicalHighlighter{
+			tasks: highlightTasks,
+		},
+		lb:             mockLb,
+		schema:         newSchemaInfo(schema),
+		request:        req,
+		collectionName: collName,
+		SearchRequest: &internalpb.SearchRequest{
+			CollectionID: 0,
+		},
+	}
+
+	op, err := opFactory[highlightOp](searchTask, map[string]any{})
+	s.Require().NoError(err)
+
+	// mockery
+	mockLb.EXPECT().ExecuteOneChannel(mock.Anything, mock.Anything).Run(func(ctx context.Context, workload shardclient.CollectionWorkLoad) {
+		qn := mocks.NewMockQueryNodeClient(s.T())
+		qn.EXPECT().GetHighlight(mock.Anything, mock.Anything).Return(
+			&querypb.GetHighlightResponse{
+				Status:  merr.Success(),
+				Results: []*querypb.HighlightResult{},
+			}, nil)
+		workload.Exec(ctx, 0, qn, "test_chan")
+	}).Return(nil)
+
+	_, err = op.run(ctx, s.span, &milvuspb.SearchResults{
+		Results: &schemapb.SearchResultData{
+			TopK:  3,
+			Topks: []int64{1},
+			FieldsData: []*schemapb.FieldData{{
+				FieldName: testVarCharField,
+				FieldId:   100,
+				Field: &schemapb.FieldData_Scalars{
+					Scalars: &schemapb.ScalarField{
+						Data: &schemapb.ScalarField_StringData{
+							StringData: &schemapb.StringArray{
+								Data: []string{"match text"},
+							},
+						},
+					},
+				},
+			}},
+		},
+	})
+	s.NoError(err)
+}
+
 func (s *SearchPipelineSuite) TestSearchPipeline() {
 	collectionName := "test"
 	task := &searchTask{
@@ -295,8 +390,11 @@ func (s *SearchPipelineSuite) TestSearchPipeline() {
 		queryInfos:             []*planpb.QueryInfo{{}},
 		translatedOutputFields: []string{"intField"},
 	}
+
 	pipeline, err := newPipeline(searchPipe, task)
 	s.NoError(err)
+	pipeline.AddNodes(task, filterFieldNode)
+
 	sr := genTestSearchResultData(2, 10, schemapb.DataType_Int64, "intField", 101, false)
 	results, storageCost, err := pipeline.Run(context.Background(), s.span, []*internalpb.SearchResults{sr}, segcore.StorageCost{ScannedRemoteBytes: 100, ScannedTotalBytes: 250})
 	s.NoError(err)
@@ -363,6 +461,8 @@ func (s *SearchPipelineSuite) TestSearchPipelineWithRequery() {
 
 	pipeline, err := newPipeline(searchWithRequeryPipe, task)
 	s.NoError(err)
+	pipeline.AddNodes(task, filterFieldNode)
+
 	results, storageCost, err := pipeline.Run(context.Background(), s.span, []*internalpb.SearchResults{
 		genTestSearchResultData(2, 10, schemapb.DataType_Int64, "intField", 101, false),
 	}, segcore.StorageCost{ScannedRemoteBytes: 100, ScannedTotalBytes: 200})
@@ -435,6 +535,7 @@ func (s *SearchPipelineSuite) TestSearchWithRerankPipe() {
 
 	pipeline, err := newPipeline(searchWithRerankPipe, task)
 	s.NoError(err)
+	pipeline.AddNodes(task, filterFieldNode)
 
 	searchResults := genTestSearchResultData(2, 10, schemapb.DataType_Int64, "intField", 101, false)
 	results, _, err := pipeline.Run(context.Background(), s.span, []*internalpb.SearchResults{searchResults}, segcore.StorageCost{})
@@ -518,6 +619,7 @@ func (s *SearchPipelineSuite) TestSearchWithRerankRequeryPipe() {
 
 	pipeline, err := newPipeline(searchWithRerankRequeryPipe, task)
 	s.NoError(err)
+	pipeline.AddNodes(task, filterFieldNode)
 
 	searchResults := genTestSearchResultData(2, 10, schemapb.DataType_Int64, "intField", 101, false)
 	results, storageCost, err := pipeline.Run(context.Background(), s.span, []*internalpb.SearchResults{searchResults}, segcore.StorageCost{})
@@ -552,6 +654,7 @@ func (s *SearchPipelineSuite) TestHybridSearchPipe() {
 
 	pipeline, err := newPipeline(hybridSearchPipe, task)
 	s.NoError(err)
+	pipeline.AddNodes(task, filterFieldNode)
 
 	f1 := genTestSearchResultData(2, 10, schemapb.DataType_Int64, "intField", 101, true)
 	f2 := genTestSearchResultData(2, 10, schemapb.DataType_Int64, "intField", 101, true)
@@ -665,6 +768,7 @@ func (s *SearchPipelineSuite) TestHybridSearchWithRequeryAndRerankByDataPipe() {
 
 	pipeline, err := newPipeline(hybridSearchWithRequeryAndRerankByFieldDataPipe, task)
 	s.NoError(err)
+	pipeline.AddNodes(task, filterFieldNode)
 
 	d1 := genTestSearchResultData(2, 10, schemapb.DataType_Int64, "intField", 101, true)
 	d2 := genTestSearchResultData(2, 10, schemapb.DataType_Int64, "intField", 101, true)
@@ -707,6 +811,7 @@ func (s *SearchPipelineSuite) TestHybridSearchWithRequeryPipe() {
 
 	pipeline, err := newPipeline(hybridSearchWithRequeryPipe, task)
 	s.NoError(err)
+	pipeline.AddNodes(task, filterFieldNode)
 
 	d1 := genTestSearchResultData(2, 10, schemapb.DataType_Int64, "intField", 101, true)
 	d2 := genTestSearchResultData(2, 10, schemapb.DataType_Int64, "intField", 101, true)

internal/proxy/task.go

@@ -65,6 +65,7 @@ const (
 	StrictCastKey        = "strict_cast"
 	RankGroupScorer      = "rank_group_scorer"
 	AnnsFieldKey         = "anns_field"
+	AnalyzerKey          = "analyzer_name"
 	TopKKey              = "topk"
 	NQKey                = "nq"
 	MetricTypeKey        = common.MetricTypeKey
@@ -114,6 +115,7 @@ const (
 	ListResourceGroupsTaskName    = "ListResourceGroupsTask"
 	DescribeResourceGroupTaskName = "DescribeResourceGroupTask"
 	RunAnalyzerTaskName           = "RunAnalyzer"
+	HighlightTaskName             = "Highlight"
 
 	CreateDatabaseTaskName   = "CreateCollectionTask"
 	DropDatabaseTaskName     = "DropDatabaseTaskName"
@@ -3144,6 +3146,95 @@ func (t *RunAnalyzerTask) PostExecute(ctx context.Context) error {
 	return nil
 }
 
+// git highlight after search
+type HighlightTask struct {
+	baseTask
+	Condition
+	*querypb.GetHighlightRequest
+	ctx            context.Context
+	collectionName string
+	collectionID   typeutil.UniqueID
+	dbName         string
+	lb             shardclient.LBPolicy
+
+	result *querypb.GetHighlightResponse
+}
+
+func (t *HighlightTask) TraceCtx() context.Context {
+	return t.ctx
+}
+
+func (t *HighlightTask) ID() UniqueID {
+	return t.Base.MsgID
+}
+
+func (t *HighlightTask) SetID(uid UniqueID) {
+	t.Base.MsgID = uid
+}
+
+func (t *HighlightTask) Name() string {
+	return HighlightTaskName
+}
+
+func (t *HighlightTask) Type() commonpb.MsgType {
+	return t.Base.MsgType
+}
+
+func (t *HighlightTask) BeginTs() Timestamp {
+	return t.Base.Timestamp
+}
+
+func (t *HighlightTask) EndTs() Timestamp {
+	return t.Base.Timestamp
+}
+
+func (t *HighlightTask) SetTs(ts Timestamp) {
+	t.Base.Timestamp = ts
+}
+
+func (t *HighlightTask) OnEnqueue() error {
+	if t.Base == nil {
+		t.Base = commonpbutil.NewMsgBase()
+	}
+	t.Base.MsgType = commonpb.MsgType_Undefined
+	t.Base.SourceID = paramtable.GetNodeID()
+	return nil
+}
+
+func (t *HighlightTask) PreExecute(ctx context.Context) error {
+	return nil
+}
+
+func (t *HighlightTask) getHighlightOnShardleader(ctx context.Context, nodeID int64, qn types.QueryNodeClient, channel string) error {
+	t.GetHighlightRequest.Channel = channel
+	resp, err := qn.GetHighlight(ctx, t.GetHighlightRequest)
+	if err != nil {
+		return err
+	}
+
+	if err := merr.Error(resp.GetStatus()); err != nil {
+		return err
+	}
+	t.result = resp
+	return nil
+}
+
+func (t *HighlightTask) Execute(ctx context.Context) error {
+	err := t.lb.ExecuteOneChannel(ctx, shardclient.CollectionWorkLoad{
+		Db:             t.dbName,
+		CollectionName: t.collectionName,
+		CollectionID:   t.collectionID,
+		Nq:             int64(len(t.GetTopks()) * len(t.GetTasks())),
+		Exec:           t.getHighlightOnShardleader,
+	})
+
+	return err
+}
+
+func (t *HighlightTask) PostExecute(ctx context.Context) error {
+	return nil
+}
+
 // isIgnoreGrowing is used to check if the request should ignore growing
 func isIgnoreGrowing(params []*commonpb.KeyValuePair) (bool, error) {
 	for _, kv := range params {

internal/proxy/task_search.go

@@ -80,7 +80,7 @@ type searchTask struct {
 	translatedOutputFields []string
 	userOutputFields       []string
 	userDynamicFields      []string
-
+	highlighter            Highlighter
 	resultBuf              *typeutil.ConcurrentSet[*internalpb.SearchResults]
 
 	partitionIDsSet *typeutil.ConcurrentSet[UniqueID]
@@ -466,12 +466,13 @@ func (t *searchTask) initAdvancedSearchRequest(ctx context.Context) error {
 		}
 
 		// set analyzer name for sub search
-		analyzer, err := funcutil.GetAttrByKeyFromRepeatedKV("analyzer_name", subReq.GetSearchParams())
+		analyzer, err := funcutil.GetAttrByKeyFromRepeatedKV(AnalyzerKey, subReq.GetSearchParams())
 		if err == nil {
 			internalSubReq.AnalyzerName = analyzer
 		}
 
 		internalSubReq.FieldId = queryInfo.GetQueryFieldId()
+
 		queryFieldIDs = append(queryFieldIDs, internalSubReq.FieldId)
 		// set PartitionIDs for sub search
 		if t.partitionKeyMode {
@@ -557,6 +558,67 @@ func (t *searchTask) fillResult() {
 	t.result.CollectionName = t.collectionName
 }
 
+func (t *searchTask) getBM25SearchTexts(placeholder []byte) ([]string, error) {
+	pb := &commonpb.PlaceholderGroup{}
+	proto.Unmarshal(placeholder, pb)
+
+	if len(pb.Placeholders) != 1 || len(pb.Placeholders[0].Values) == 0 {
+		return nil, merr.WrapErrParameterInvalidMsg("please provide varchar/text for BM25 Function based search")
+	}
+
+	holder := pb.Placeholders[0]
+	if holder.Type != commonpb.PlaceholderType_VarChar {
+		return nil, merr.WrapErrParameterInvalidMsg(fmt.Sprintf("please provide varchar/text for BM25 Function based search, got %s", holder.Type.String()))
+	}
+
+	texts := funcutil.GetVarCharFromPlaceholder(holder)
+	return texts, nil
+}
+
+func (t *searchTask) createLexicalHighlighter(highlighter *commonpb.Highlighter, metricType string, annsField int64, placeholder []byte, analyzerName string) error {
+	h, err := NewLexicalHighlighter(highlighter)
+	if err != nil {
+		return err
+	}
+	t.highlighter = h
+	if h.highlightSearch {
+		if metricType != metric.BM25 {
+			return merr.WrapErrParameterInvalidMsg(`Search highlight only support with metric type "BM25" but was: %s`, t.SearchRequest.GetMetricType())
+		}
+		function, ok := getBM25FunctionOfAnnsField(annsField, t.schema.GetFunctions())
+		if !ok {
+			return merr.WrapErrServiceInternal(`Search with highlight failed, input field of BM25 annsField not found`)
+		}
+		fieldId := function.InputFieldIds[0]
+		fieldName := function.InputFieldNames[0]
+		// set bm25 search text as highlight search texts
+		texts, err := t.getBM25SearchTexts(placeholder)
+		if err != nil {
+			return err
+		}
+		err = h.addTaskWithSearchText(fieldId, fieldName, analyzerName, texts)
+		if err != nil {
+			return err
+		}
+
+		return h.initHighlightQueries(t)
+	}
+	return nil
+}
+
+func (t *searchTask) addHighlightTask(highlighter *commonpb.Highlighter, metricType string, annsField int64, placeholder []byte, analyzerName string) error {
+	if highlighter == nil {
+		return nil
+	}
+
+	switch highlighter.GetType() {
+	case commonpb.HighlightType_Lexical:
+		return t.createLexicalHighlighter(highlighter, metricType, annsField, placeholder, analyzerName)
+	default:
+		return merr.WrapErrParameterInvalidMsg("unsupported highlight type: %v", highlighter.GetType())
+	}
+}
+
 func (t *searchTask) initSearchRequest(ctx context.Context) error {
 	ctx, sp := otel.Tracer(typeutil.ProxyRole).Start(ctx, "init search request")
 	defer sp.End()
@@ -579,10 +641,24 @@ func (t *searchTask) initSearchRequest(ctx context.Context) error {
 		}
 	}
 
+	analyzer, err := funcutil.GetAttrByKeyFromRepeatedKV(AnalyzerKey, t.request.GetSearchParams())
+	if err == nil {
+		t.SearchRequest.AnalyzerName = analyzer
+	}
+
 	t.isIterator = isIterator
 	t.SearchRequest.Offset = offset
 	t.SearchRequest.FieldId = queryInfo.GetQueryFieldId()
 
+	if err := t.addHighlightTask(t.request.GetHighlighter(), queryInfo.GetMetricType(), queryInfo.GetQueryFieldId(), t.request.GetPlaceholderGroup(), t.SearchRequest.GetAnalyzerName()); err != nil {
+		return err
+	}
+
+	// add highlight field ids to output fields id
+	if t.highlighter != nil {
+		t.SearchRequest.OutputFieldsId = append(t.SearchRequest.OutputFieldsId, t.highlighter.FieldIDs()...)
+	}
+
 	if t.partitionKeyMode {
 		// isolation has tighter constraint, check first
 		mvErr := setQueryInfoIfMvEnable(queryInfo, t, plan)
@@ -632,13 +708,6 @@ func (t *searchTask) initSearchRequest(ctx context.Context) error {
 	t.SearchRequest.GroupByFieldId = queryInfo.GroupByFieldId
 	t.SearchRequest.GroupSize = queryInfo.GroupSize
 
-	if t.SearchRequest.MetricType == metric.BM25 {
-		analyzer, err := funcutil.GetAttrByKeyFromRepeatedKV("analyzer_name", t.request.GetSearchParams())
-		if err == nil {
-			t.SearchRequest.AnalyzerName = analyzer
-		}
-	}
-
 	if embedding.HasNonBM25Functions(t.schema.CollectionSchema.Functions, []int64{queryInfo.GetQueryFieldId()}) {
 		ctx, sp := otel.Tracer(typeutil.ProxyRole).Start(ctx, "Proxy-Search-call-function-udf")
 		defer sp.End()
@@ -813,7 +882,7 @@ func (t *searchTask) PostExecute(ctx context.Context) error {
 	t.isRecallEvaluation = isRecallEvaluation
 
 	// call pipeline
-	pipeline, err := newBuiltInPipeline(t)
+	pipeline, err := newSearchPipeline(t)
 	if err != nil {
 		log.Warn("Faild to create post process pipeline")
 		return err

internal/proxy/task_search_test.go

@@ -4885,3 +4885,198 @@ func TestSearchTask_InitSearchRequestWithStructArrayFields(t *testing.T) {
 		})
 	}
 }
+
+func TestSearchTask_AddHighlightTask(t *testing.T) {
+	paramtable.Init()
+
+	// Create a schema with BM25 function
+	schema := &schemapb.CollectionSchema{
+		Name: "test_highlight_collection",
+		Fields: []*schemapb.FieldSchema{
+			{
+				FieldID:  100,
+				Name:     "text_field",
+				DataType: schemapb.DataType_VarChar,
+			},
+			{
+				FieldID:  101,
+				Name:     "sparse_field",
+				DataType: schemapb.DataType_SparseFloatVector,
+			},
+		},
+		Functions: []*schemapb.FunctionSchema{
+			{
+				Name:             "bm25_func",
+				Type:             schemapb.FunctionType_BM25,
+				InputFieldNames:  []string{"text_field"},
+				InputFieldIds:    []int64{100},
+				OutputFieldNames: []string{"sparse_field"},
+				OutputFieldIds:   []int64{101},
+			},
+		},
+	}
+
+	placeholder := &commonpb.PlaceholderGroup{
+		Placeholders: []*commonpb.PlaceholderValue{{
+			Type:   commonpb.PlaceholderType_VarChar,
+			Values: [][]byte{[]byte("test_str")},
+		}},
+	}
+
+	placeholderBytes, err := proto.Marshal(placeholder)
+	require.NoError(t, err)
+
+	t.Run("lexical highlight success", func(t *testing.T) {
+		task := &searchTask{
+			schema: &schemaInfo{
+				CollectionSchema: schema,
+			},
+		}
+
+		highlighter := &commonpb.Highlighter{
+			Type:   commonpb.HighlightType_Lexical,
+			Params: []*commonpb.KeyValuePair{{Key: HighlightSearchTextKey, Value: "true"}},
+		}
+
+		err := task.addHighlightTask(highlighter, metric.BM25, 101, placeholderBytes, "")
+		assert.NoError(t, err)
+
+		h, ok := task.highlighter.(*LexicalHighlighter)
+		require.True(t, ok)
+		require.Equal(t, 1, len(h.tasks))
+		assert.Equal(t, int64(100), h.tasks[100].FieldId)
+		assert.Equal(t, "text_field", h.tasks[100].FieldName)
+	})
+
+	t.Run("Lexical highlight with custom tags", func(t *testing.T) {
+		task := &searchTask{
+			schema: &schemaInfo{
+				CollectionSchema: schema,
+			},
+		}
+
+		highlighter := &commonpb.Highlighter{
+			Type:   commonpb.HighlightType_Lexical,
+			Params: []*commonpb.KeyValuePair{{Key: HighlightSearchTextKey, Value: "true"}, {Key: "pre_tags", Value: `["<b>"]`}, {Key: "post_tags", Value: `["</b>"]`}},
+		}
+
+		err := task.addHighlightTask(highlighter, metric.BM25, 101, placeholderBytes, "")
+		assert.NoError(t, err)
+
+		h, ok := task.highlighter.(*LexicalHighlighter)
+		require.True(t, ok)
+		assert.Equal(t, 1, len(h.preTags))
+		assert.Equal(t, []byte("<b>"), h.preTags[0])
+		assert.Equal(t, 1, len(h.postTags))
+		assert.Equal(t, []byte("</b>"), h.postTags[0])
+	})
+
+	t.Run("lexical highlight with wrong metric type", func(t *testing.T) {
+		task := &searchTask{
+			schema: &schemaInfo{
+				CollectionSchema: schema,
+			},
+			SearchRequest: &internalpb.SearchRequest{},
+			request:       &milvuspb.SearchRequest{},
+		}
+
+		highlighter := &commonpb.Highlighter{
+			Type:   commonpb.HighlightType_Lexical,
+			Params: []*commonpb.KeyValuePair{{Key: HighlightSearchTextKey, Value: "true"}},
+		}
+
+		err := task.addHighlightTask(highlighter, metric.L2, 101, placeholderBytes, "")
+		assert.Error(t, err)
+	})
+
+	t.Run("lexical highlight with invalid pre_tags type", func(t *testing.T) {
+		task := &searchTask{
+			schema: &schemaInfo{
+				CollectionSchema: schema,
+			},
+		}
+
+		highlighter := &commonpb.Highlighter{
+			Type:   commonpb.HighlightType_Lexical,
+			Params: []*commonpb.KeyValuePair{{Key: HighlightSearchTextKey, Value: "true"}, {Key: "pre_tags", Value: "not_a_list"}},
+		}
+
+		err := task.addHighlightTask(highlighter, metric.BM25, 101, placeholderBytes, "")
+		assert.Error(t, err)
+	})
+
+	t.Run("default lexical highlight but not BM25 field", func(t *testing.T) {
+		schemaWithoutBM25 := &schemapb.CollectionSchema{
+			Name: "test_collection",
+			Fields: []*schemapb.FieldSchema{
+				{
+					FieldID:  100,
+					Name:     "vector_field",
+					DataType: schemapb.DataType_FloatVector,
+				},
+			},
+		}
+
+		task := &searchTask{
+			schema: &schemaInfo{
+				CollectionSchema: schemaWithoutBM25,
+			},
+		}
+
+		highlighter := &commonpb.Highlighter{
+			Type:   commonpb.HighlightType_Lexical,
+			Params: []*commonpb.KeyValuePair{{Key: HighlightSearchTextKey, Value: "true"}},
+		}
+
+		err := task.addHighlightTask(highlighter, metric.BM25, 100, placeholderBytes, "")
+		assert.Error(t, err)
+	})
+
+	t.Run("highlight without highlight search text", func(t *testing.T) {
+		task := &searchTask{
+			schema: &schemaInfo{
+				CollectionSchema: schema,
+			},
+		}
+
+		highlighter := &commonpb.Highlighter{
+			Type:   commonpb.HighlightType_Lexical,
+			Params: []*commonpb.KeyValuePair{{Key: HighlightSearchTextKey, Value: "false"}},
+		}
+
+		err := task.addHighlightTask(highlighter, metric.BM25, 101, placeholderBytes, "")
+		assert.NoError(t, err)
+	})
+
+	t.Run("highlight with invalid highlight search key", func(t *testing.T) {
+		task := &searchTask{
+			schema: &schemaInfo{
+				CollectionSchema: schema,
+			},
+		}
+
+		highlighter := &commonpb.Highlighter{
+			Type:   commonpb.HighlightType_Lexical,
+			Params: []*commonpb.KeyValuePair{{Key: HighlightSearchTextKey, Value: "invalid"}},
+		}
+
+		err := task.addHighlightTask(highlighter, metric.BM25, 101, placeholderBytes, "")
+		assert.Error(t, err)
+	})
+
+	t.Run("highlight with unknown type", func(t *testing.T) {
+		task := &searchTask{
+			schema: &schemaInfo{
+				CollectionSchema: schema,
+			},
+		}
+
+		highlighter := &commonpb.Highlighter{
+			Type:   4,
+			Params: []*commonpb.KeyValuePair{{Key: HighlightSearchTextKey, Value: "true"}},
+		}
+
+		err := task.addHighlightTask(highlighter, metric.BM25, 101, placeholderBytes, "")
+		assert.Error(t, err)
+	})
+}

internal/proxy/task_test.go

@@ -39,6 +39,7 @@ import (
 	"github.com/milvus-io/milvus/internal/allocator"
 	"github.com/milvus-io/milvus/internal/json"
 	"github.com/milvus-io/milvus/internal/mocks"
+	"github.com/milvus-io/milvus/internal/proxy/shardclient"
 	"github.com/milvus-io/milvus/internal/querycoordv2/meta"
 	"github.com/milvus-io/milvus/internal/util/function/embedding"
 	"github.com/milvus-io/milvus/pkg/v2/common"
@@ -5497,3 +5498,237 @@ func TestAlterCollection_AllowInsertAutoID_AutoIDFalse(t *testing.T) {
 	assert.Error(t, err)
 	assert.Equal(t, merr.Code(merr.ErrParameterInvalid), merr.Code(err))
 }
+
+func TestHighlightTask(t *testing.T) {
+	paramtable.Init()
+	ctx := context.Background()
+
+	t.Run("basic methods", func(t *testing.T) {
+		task := &HighlightTask{
+			ctx: ctx,
+			GetHighlightRequest: &querypb.GetHighlightRequest{
+				Base: commonpbutil.NewMsgBase(),
+			},
+			Condition: NewTaskCondition(ctx),
+		}
+
+		t.Run("traceCtx", func(t *testing.T) {
+			traceCtx := task.TraceCtx()
+			assert.NotNil(t, traceCtx)
+			assert.Equal(t, ctx, traceCtx)
+		})
+
+		t.Run("id", func(t *testing.T) {
+			id := UniqueID(uniquegenerator.GetUniqueIntGeneratorIns().GetInt())
+			task.SetID(id)
+			assert.Equal(t, id, task.ID())
+		})
+
+		t.Run("name", func(t *testing.T) {
+			assert.Equal(t, HighlightTaskName, task.Name())
+		})
+
+		t.Run("type", func(t *testing.T) {
+			assert.Equal(t, commonpb.MsgType_Undefined, task.Type())
+		})
+
+		t.Run("ts", func(t *testing.T) {
+			ts := Timestamp(time.Now().UnixNano())
+			task.SetTs(ts)
+			assert.Equal(t, ts, task.BeginTs())
+			assert.Equal(t, ts, task.EndTs())
+		})
+	})
+
+	t.Run("OnEnqueue", func(t *testing.T) {
+		task := &HighlightTask{
+			ctx:                 ctx,
+			GetHighlightRequest: &querypb.GetHighlightRequest{},
+			Condition:           NewTaskCondition(ctx),
+		}
+
+		err := task.OnEnqueue()
+		assert.NoError(t, err)
+		assert.NotNil(t, task.Base)
+		assert.Equal(t, commonpb.MsgType_Undefined, task.Base.MsgType)
+		assert.Equal(t, paramtable.GetNodeID(), task.Base.SourceID)
+	})
+
+	t.Run("PreExecute", func(t *testing.T) {
+		task := &HighlightTask{
+			ctx: ctx,
+			GetHighlightRequest: &querypb.GetHighlightRequest{
+				Base: commonpbutil.NewMsgBase(),
+			},
+			Condition: NewTaskCondition(ctx),
+		}
+
+		err := task.PreExecute(ctx)
+		assert.NoError(t, err)
+	})
+
+	t.Run("getHighlightOnShardleader success", func(t *testing.T) {
+		task := &HighlightTask{
+			ctx: ctx,
+			GetHighlightRequest: &querypb.GetHighlightRequest{
+				Base:  commonpbutil.NewMsgBase(),
+				Topks: []int64{10},
+				Tasks: []*querypb.HighlightTask{
+					{},
+				},
+			},
+			Condition: NewTaskCondition(ctx),
+		}
+
+		mockQN := mocks.NewMockQueryNodeClient(t)
+		expectedResp := &querypb.GetHighlightResponse{
+			Status: merr.Success(),
+			Results: []*querypb.HighlightResult{
+				{
+					Fragments: []*querypb.HighlightFragment{
+						{
+							StartOffset: 0,
+							EndOffset:   10,
+							Offsets:     []int64{0, 5, 5, 10},
+						},
+					},
+				},
+			},
+		}
+
+		mockQN.EXPECT().GetHighlight(mock.Anything, mock.Anything).Return(expectedResp, nil)
+
+		err := task.getHighlightOnShardleader(ctx, 1, mockQN, "test_channel")
+		assert.NoError(t, err)
+		assert.NotNil(t, task.result)
+		assert.Equal(t, expectedResp, task.result)
+		assert.Equal(t, "test_channel", task.GetHighlightRequest.Channel)
+	})
+
+	t.Run("getHighlightOnShardleader rpc error", func(t *testing.T) {
+		task := &HighlightTask{
+			ctx: ctx,
+			GetHighlightRequest: &querypb.GetHighlightRequest{
+				Base: commonpbutil.NewMsgBase(),
+			},
+			Condition: NewTaskCondition(ctx),
+		}
+
+		mockQN := mocks.NewMockQueryNodeClient(t)
+		mockQN.EXPECT().GetHighlight(mock.Anything, mock.Anything).Return(nil, errors.New("rpc error"))
+
+		err := task.getHighlightOnShardleader(ctx, 1, mockQN, "test_channel")
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "rpc error")
+	})
+
+	t.Run("getHighlightOnShardleader status error", func(t *testing.T) {
+		task := &HighlightTask{
+			ctx: ctx,
+			GetHighlightRequest: &querypb.GetHighlightRequest{
+				Base: commonpbutil.NewMsgBase(),
+			},
+			Condition: NewTaskCondition(ctx),
+		}
+
+		mockQN := mocks.NewMockQueryNodeClient(t)
+		expectedResp := &querypb.GetHighlightResponse{
+			Status: merr.Status(errors.New("status error")),
+		}
+
+		mockQN.EXPECT().GetHighlight(mock.Anything, mock.Anything).Return(expectedResp, nil)
+
+		err := task.getHighlightOnShardleader(ctx, 1, mockQN, "test_channel")
+		assert.Error(t, err)
+	})
+
+	t.Run("Execute success", func(t *testing.T) {
+		task := &HighlightTask{
+			ctx:            ctx,
+			collectionName: "test_collection",
+			collectionID:   100,
+			dbName:         "default",
+			GetHighlightRequest: &querypb.GetHighlightRequest{
+				Base:  commonpbutil.NewMsgBase(),
+				Topks: []int64{10, 20},
+				Tasks: []*querypb.HighlightTask{
+					{},
+					{},
+				},
+			},
+			Condition: NewTaskCondition(ctx),
+		}
+
+		mockLB := shardclient.NewMockLBPolicy(t)
+		mockQN := mocks.NewMockQueryNodeClient(t)
+
+		expectedResp := &querypb.GetHighlightResponse{
+			Status: merr.Success(),
+			Results: []*querypb.HighlightResult{
+				{
+					Fragments: []*querypb.HighlightFragment{
+						{
+							StartOffset: 0,
+							EndOffset:   10,
+							Offsets:     []int64{0, 5, 5, 10},
+						},
+					},
+				},
+			},
+		}
+
+		mockQN.EXPECT().GetHighlight(mock.Anything, mock.Anything).Return(expectedResp, nil)
+
+		mockLB.EXPECT().ExecuteOneChannel(mock.Anything, mock.Anything).Run(
+			func(ctx context.Context, workload shardclient.CollectionWorkLoad) {
+				assert.Equal(t, "default", workload.Db)
+				assert.Equal(t, "test_collection", workload.CollectionName)
+				assert.Equal(t, int64(100), workload.CollectionID)
+				assert.Equal(t, int64(4), workload.Nq) // len(topks) * len(tasks) = 2 * 2 = 4
+				err := workload.Exec(ctx, 1, mockQN, "test_channel")
+				assert.NoError(t, err)
+			},
+		).Return(nil)
+
+		task.lb = mockLB
+
+		err := task.Execute(ctx)
+		assert.NoError(t, err)
+		assert.NotNil(t, task.result)
+	})
+
+	t.Run("Execute lb error", func(t *testing.T) {
+		task := &HighlightTask{
+			ctx:            ctx,
+			collectionName: "test_collection",
+			collectionID:   100,
+			dbName:         "default",
+			GetHighlightRequest: &querypb.GetHighlightRequest{
+				Base: commonpbutil.NewMsgBase(),
+			},
+			Condition: NewTaskCondition(ctx),
+		}
+
+		mockLB := shardclient.NewMockLBPolicy(t)
+		mockLB.EXPECT().ExecuteOneChannel(mock.Anything, mock.Anything).Return(errors.New("lb error"))
+
+		task.lb = mockLB
+
+		err := task.Execute(ctx)
+		assert.Error(t, err)
+		assert.Contains(t, err.Error(), "lb error")
+	})
+
+	t.Run("PostExecute", func(t *testing.T) {
+		task := &HighlightTask{
+			ctx: ctx,
+			GetHighlightRequest: &querypb.GetHighlightRequest{
+				Base: commonpbutil.NewMsgBase(),
+			},
+			Condition: NewTaskCondition(ctx),
+		}
+
+		err := task.PostExecute(ctx)
+		assert.NoError(t, err)
+	})
+}

internal/proxy/util.go

@@ -3040,3 +3040,9 @@ func genFunctionFields(ctx context.Context, insertMsg *msgstream.InsertMsg, sche
 	}
 	return nil
 }
+
+func getBM25FunctionOfAnnsField(fieldID int64, functions []*schemapb.FunctionSchema) (*schemapb.FunctionSchema, bool) {
+	return lo.Find(functions, func(function *schemapb.FunctionSchema) bool {
+		return function.GetType() == schemapb.FunctionType_BM25 && function.OutputFieldIds[0] == fieldID
+	})
+}

internal/querycoordv2/mocks/mock_querynode.go

@@ -324,6 +324,65 @@ func (_c *MockQueryNodeServer_GetDataDistribution_Call) RunAndReturn(run func(co
 	return _c
 }
 
+// GetHighlight provides a mock function with given fields: _a0, _a1
+func (_m *MockQueryNodeServer) GetHighlight(_a0 context.Context, _a1 *querypb.GetHighlightRequest) (*querypb.GetHighlightResponse, error) {
+	ret := _m.Called(_a0, _a1)
+
+	if len(ret) == 0 {
+		panic("no return value specified for GetHighlight")
+	}
+
+	var r0 *querypb.GetHighlightResponse
+	var r1 error
+	if rf, ok := ret.Get(0).(func(context.Context, *querypb.GetHighlightRequest) (*querypb.GetHighlightResponse, error)); ok {
+		return rf(_a0, _a1)
+	}
+	if rf, ok := ret.Get(0).(func(context.Context, *querypb.GetHighlightRequest) *querypb.GetHighlightResponse); ok {
+		r0 = rf(_a0, _a1)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(*querypb.GetHighlightResponse)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func(context.Context, *querypb.GetHighlightRequest) error); ok {
+		r1 = rf(_a0, _a1)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
+// MockQueryNodeServer_GetHighlight_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'GetHighlight'
+type MockQueryNodeServer_GetHighlight_Call struct {
+	*mock.Call
+}
+
+// GetHighlight is a helper method to define mock.On call
+//   - _a0 context.Context
+//   - _a1 *querypb.GetHighlightRequest
+func (_e *MockQueryNodeServer_Expecter) GetHighlight(_a0 interface{}, _a1 interface{}) *MockQueryNodeServer_GetHighlight_Call {
+	return &MockQueryNodeServer_GetHighlight_Call{Call: _e.mock.On("GetHighlight", _a0, _a1)}
+}
+
+func (_c *MockQueryNodeServer_GetHighlight_Call) Run(run func(_a0 context.Context, _a1 *querypb.GetHighlightRequest)) *MockQueryNodeServer_GetHighlight_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run(args[0].(context.Context), args[1].(*querypb.GetHighlightRequest))
+	})
+	return _c
+}
+
+func (_c *MockQueryNodeServer_GetHighlight_Call) Return(_a0 *querypb.GetHighlightResponse, _a1 error) *MockQueryNodeServer_GetHighlight_Call {
+	_c.Call.Return(_a0, _a1)
+	return _c
+}
+
+func (_c *MockQueryNodeServer_GetHighlight_Call) RunAndReturn(run func(context.Context, *querypb.GetHighlightRequest) (*querypb.GetHighlightResponse, error)) *MockQueryNodeServer_GetHighlight_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
 // GetMetrics provides a mock function with given fields: _a0, _a1
 func (_m *MockQueryNodeServer) GetMetrics(_a0 context.Context, _a1 *milvuspb.GetMetricsRequest) (*milvuspb.GetMetricsResponse, error) {
 	ret := _m.Called(_a0, _a1)

internal/querynodev2/delegator/delegator.go

@@ -104,6 +104,7 @@ type ShardDelegator interface {
 
 	// analyzer
 	RunAnalyzer(ctx context.Context, req *querypb.RunAnalyzerRequest) ([]*milvuspb.AnalyzerResult, error)
+	GetHighlight(ctx context.Context, req *querypb.GetHighlightRequest) ([]*querypb.HighlightResult, error)
 
 	// control
 	Serviceable() bool

internal/querynodev2/delegator/delegator_data.go

@@ -29,6 +29,7 @@ import (
 	"google.golang.org/protobuf/proto"
 
 	"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-proto/go-api/v2/msgpb"
 	"github.com/milvus-io/milvus-proto/go-api/v2/schemapb"
 	"github.com/milvus-io/milvus/internal/querynodev2/cluster"
@@ -1001,3 +1002,87 @@ func (sd *shardDelegator) DropIndex(ctx context.Context, req *querypb.DropIndexR
 	}
 	return nil
 }
+
+func (sd *shardDelegator) GetHighlight(ctx context.Context, req *querypb.GetHighlightRequest) ([]*querypb.HighlightResult, error) {
+	result := []*querypb.HighlightResult{}
+	for _, task := range req.GetTasks() {
+		if len(task.GetTexts()) != int(task.GetSearchTextNum()+task.GetCorpusTextNum())+len(task.GetQueries()) {
+			return nil, errors.Errorf("package highlight texts error, num of texts not equal the expected num %d:%d", len(task.GetTexts()), int(task.GetSearchTextNum()+task.GetCorpusTextNum())+len(task.GetQueries()))
+		}
+		analyzer, ok := sd.analyzerRunners[task.GetFieldId()]
+		if !ok {
+			return nil, merr.WrapErrParameterInvalidMsg("get highlight failed, the highlight field not found, %s:%d", task.GetFieldName(), task.GetFieldId())
+		}
+		topks := req.GetTopks()
+		var results [][]*milvuspb.AnalyzerToken
+		var err error
+
+		if len(analyzer.GetInputFields()) == 1 {
+			results, err = analyzer.BatchAnalyze(true, false, task.GetTexts())
+			if err != nil {
+				return nil, err
+			}
+		} else if len(analyzer.GetInputFields()) == 2 {
+			// use analyzer names if analyzer need two input field
+			results, err = analyzer.BatchAnalyze(true, false, task.GetTexts(), task.GetAnalyzerNames())
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		// analyze result of search text
+		searchResults := results[0:task.SearchTextNum]
+		// analyze result of query text
+		queryResults := results[task.SearchTextNum : task.SearchTextNum+int64(len(task.Queries))]
+		// analyze result of corpus text
+		corpusStartOffset := int(task.SearchTextNum) + len(task.Queries)
+		corpusResults := results[corpusStartOffset:]
+
+		// query for all corpus texts
+		// only support text match now
+		// build match set for all analyze result of query text
+		// TODO: support more query types
+		queryTokenSet := typeutil.NewSet[string]()
+		for _, tokens := range queryResults {
+			for _, token := range tokens {
+				queryTokenSet.Insert(token.GetToken())
+			}
+		}
+
+		corpusIdx := 0
+		for i := range len(topks) {
+			tokenSet := typeutil.NewSet[string]()
+			if len(searchResults) > i {
+				for _, token := range searchResults[i] {
+					tokenSet.Insert(token.GetToken())
+				}
+			}
+
+			for j := 0; j < int(topks[i]); j++ {
+				spans := SpanList{}
+				for _, token := range corpusResults[corpusIdx] {
+					if tokenSet.Contain(token.GetToken()) || queryTokenSet.Contain(token.GetToken()) {
+						spans = append(spans, Span{token.GetStartOffset(), token.GetEndOffset()})
+					}
+				}
+				spans = mergeOffsets(spans)
+
+				// Convert byte offsets from analyzer to rune (character) offsets
+				corpusText := task.Texts[corpusStartOffset+corpusIdx]
+				err := bytesOffsetToRuneOffset(corpusText, spans)
+				if err != nil {
+					return nil, err
+				}
+
+				frags := fetchFragmentsFromOffsets(corpusText, spans,
+					task.GetOptions().GetFragmentOffset(),
+					task.GetOptions().GetFragmentSize(),
+					task.GetOptions().GetNumOfFragments())
+				result = append(result, &querypb.HighlightResult{Fragments: frags})
+				corpusIdx++
+			}
+		}
+	}
+
+	return result, nil
+}

internal/querynodev2/delegator/delegator_test.go

@@ -1596,6 +1596,159 @@ func (s *DelegatorSuite) TestRunAnalyzer() {
 	})
 }
 
+func (s *DelegatorSuite) TestGetHighlight() {
+	ctx := context.Background()
+	s.TestCreateDelegatorWithFunction()
+
+	s.Run("field analyzer not exist", func() {
+		_, err := s.delegator.GetHighlight(ctx, &querypb.GetHighlightRequest{
+			Topks: []int64{1},
+			Tasks: []*querypb.HighlightTask{
+				{
+					FieldId: 999, // non-existent field
+				},
+			},
+		})
+		s.Require().Error(err)
+	})
+
+	s.Run("normal highlight with single analyzer", func() {
+		s.manager.Collection.PutOrRef(s.collectionID, &schemapb.CollectionSchema{
+			Fields: []*schemapb.FieldSchema{
+				{
+					FieldID:    100,
+					Name:       "text",
+					DataType:   schemapb.DataType_VarChar,
+					TypeParams: []*commonpb.KeyValuePair{{Key: "analyzer_params", Value: "{}"}},
+				},
+				{
+					FieldID:  101,
+					Name:     "sparse",
+					DataType: schemapb.DataType_SparseFloatVector,
+				},
+			},
+			Functions: []*schemapb.FunctionSchema{{
+				Type:             schemapb.FunctionType_BM25,
+				InputFieldNames:  []string{"text"},
+				InputFieldIds:    []int64{100},
+				OutputFieldNames: []string{"sparse"},
+				OutputFieldIds:   []int64{101},
+			}},
+		}, nil, &querypb.LoadMetaInfo{SchemaVersion: tsoutil.ComposeTSByTime(time.Now(), 0)})
+		s.ResetDelegator()
+
+		result, err := s.delegator.GetHighlight(ctx, &querypb.GetHighlightRequest{
+			Topks: []int64{2},
+			Tasks: []*querypb.HighlightTask{
+				{
+					FieldId:       100,
+					Texts:         []string{"test", "this is a test document", "another test case"},
+					SearchTextNum: 1,
+					CorpusTextNum: 2,
+				},
+			},
+		})
+		s.Require().NoError(err)
+		s.Require().Equal(2, len(result))
+		// Check that we got highlight results
+		s.Require().NotNil(result[0].Fragments)
+		s.Require().NotNil(result[1].Fragments)
+	})
+
+	s.Run("highlight with multi analyzer", func() {
+		s.manager.Collection.PutOrRef(s.collectionID, &schemapb.CollectionSchema{
+			Fields: []*schemapb.FieldSchema{
+				{
+					FieldID:  100,
+					Name:     "text",
+					DataType: schemapb.DataType_VarChar,
+					TypeParams: []*commonpb.KeyValuePair{{Key: "multi_analyzer_params", Value: `{
+						"by_field": "analyzer",
+    					"analyzers": {
+							"standard": {},
+							"default": {}
+						}
+					}`}},
+				},
+				{
+					FieldID:  101,
+					Name:     "sparse",
+					DataType: schemapb.DataType_SparseFloatVector,
+				},
+				{
+					FieldID:  102,
+					Name:     "analyzer",
+					DataType: schemapb.DataType_VarChar,
+				},
+			},
+			Functions: []*schemapb.FunctionSchema{{
+				Type:             schemapb.FunctionType_BM25,
+				InputFieldNames:  []string{"text"},
+				InputFieldIds:    []int64{100},
+				OutputFieldNames: []string{"sparse"},
+				OutputFieldIds:   []int64{101},
+			}},
+		}, nil, &querypb.LoadMetaInfo{SchemaVersion: tsoutil.ComposeTSByTime(time.Now(), 0)})
+		s.ResetDelegator()
+
+		// two target with two analyzer
+		result, err := s.delegator.GetHighlight(ctx, &querypb.GetHighlightRequest{
+			Topks: []int64{1, 1},
+			Tasks: []*querypb.HighlightTask{
+				{
+					FieldId:       100,
+					Texts:         []string{"test1", "test2", "this is a test1 document", "another test2 case"},
+					AnalyzerNames: []string{"default", "standard", "default", "default"},
+					SearchTextNum: 2,
+					CorpusTextNum: 2,
+				},
+			},
+		})
+		s.Require().NoError(err)
+		s.Require().Equal(2, len(result))
+	})
+
+	s.Run("empty target texts", func() {
+		s.manager.Collection.PutOrRef(s.collectionID, &schemapb.CollectionSchema{
+			Fields: []*schemapb.FieldSchema{
+				{
+					FieldID:    100,
+					Name:       "text",
+					DataType:   schemapb.DataType_VarChar,
+					TypeParams: []*commonpb.KeyValuePair{{Key: "analyzer_params", Value: "{}"}},
+				},
+				{
+					FieldID:  101,
+					Name:     "sparse",
+					DataType: schemapb.DataType_SparseFloatVector,
+				},
+			},
+			Functions: []*schemapb.FunctionSchema{{
+				Type:             schemapb.FunctionType_BM25,
+				InputFieldNames:  []string{"text"},
+				InputFieldIds:    []int64{100},
+				OutputFieldNames: []string{"sparse"},
+				OutputFieldIds:   []int64{101},
+			}},
+		}, nil, &querypb.LoadMetaInfo{SchemaVersion: tsoutil.ComposeTSByTime(time.Now(), 0)})
+		s.ResetDelegator()
+
+		result, err := s.delegator.GetHighlight(ctx, &querypb.GetHighlightRequest{
+			Topks: []int64{1},
+			Tasks: []*querypb.HighlightTask{
+				{
+					FieldId:       100,
+					Texts:         []string{"test document"},
+					SearchTextNum: 0,
+					CorpusTextNum: 1,
+				},
+			},
+		})
+		s.Require().NoError(err)
+		s.Require().NotNil(result)
+	})
+}
+
 // TestDelegatorLifetimeIntegration tests the integration of lifetime state checks with main delegator methods
 func (s *DelegatorSuite) TestDelegatorLifetimeIntegration() {
 	sd := s.delegator.(*shardDelegator)

internal/querynodev2/delegator/mock_delegator.go

@@ -289,6 +289,65 @@ func (_c *MockShardDelegator_GetDeleteBufferSize_Call) RunAndReturn(run func() (
 	return _c
 }
 
+// GetHighlight provides a mock function with given fields: ctx, req
+func (_m *MockShardDelegator) GetHighlight(ctx context.Context, req *querypb.GetHighlightRequest) ([]*querypb.HighlightResult, error) {
+	ret := _m.Called(ctx, req)
+
+	if len(ret) == 0 {
+		panic("no return value specified for GetHighlight")
+	}
+
+	var r0 []*querypb.HighlightResult
+	var r1 error
+	if rf, ok := ret.Get(0).(func(context.Context, *querypb.GetHighlightRequest) ([]*querypb.HighlightResult, error)); ok {
+		return rf(ctx, req)
+	}
+	if rf, ok := ret.Get(0).(func(context.Context, *querypb.GetHighlightRequest) []*querypb.HighlightResult); ok {
+		r0 = rf(ctx, req)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).([]*querypb.HighlightResult)
+		}
+	}
+
+	if rf, ok := ret.Get(1).(func(context.Context, *querypb.GetHighlightRequest) error); ok {
+		r1 = rf(ctx, req)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
+// MockShardDelegator_GetHighlight_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'GetHighlight'
+type MockShardDelegator_GetHighlight_Call struct {
+	*mock.Call
+}
+
+// GetHighlight is a helper method to define mock.On call
+//   - ctx context.Context
+//   - req *querypb.GetHighlightRequest
+func (_e *MockShardDelegator_Expecter) GetHighlight(ctx interface{}, req interface{}) *MockShardDelegator_GetHighlight_Call {
+	return &MockShardDelegator_GetHighlight_Call{Call: _e.mock.On("GetHighlight", ctx, req)}
+}
+
+func (_c *MockShardDelegator_GetHighlight_Call) Run(run func(ctx context.Context, req *querypb.GetHighlightRequest)) *MockShardDelegator_GetHighlight_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run(args[0].(context.Context), args[1].(*querypb.GetHighlightRequest))
+	})
+	return _c
+}
+
+func (_c *MockShardDelegator_GetHighlight_Call) Return(_a0 []*querypb.HighlightResult, _a1 error) *MockShardDelegator_GetHighlight_Call {
+	_c.Call.Return(_a0, _a1)
+	return _c
+}
+
+func (_c *MockShardDelegator_GetHighlight_Call) RunAndReturn(run func(context.Context, *querypb.GetHighlightRequest) ([]*querypb.HighlightResult, error)) *MockShardDelegator_GetHighlight_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
 // GetPartitionStatsVersions provides a mock function with given fields: ctx
 func (_m *MockShardDelegator) GetPartitionStatsVersions(ctx context.Context) map[int64]int64 {
 	ret := _m.Called(ctx)

internal/querynodev2/delegator/util.go

@@ -2,7 +2,10 @@ package delegator
 
 import (
 	"fmt"
+	"sort"
+	"unicode/utf8"
 
+	"github.com/cockroachdb/errors"
 	"go.uber.org/zap"
 	"google.golang.org/protobuf/proto"
 
@@ -10,7 +13,9 @@ import (
 	"github.com/milvus-io/milvus/pkg/v2/log"
 	"github.com/milvus-io/milvus/pkg/v2/proto/internalpb"
 	"github.com/milvus-io/milvus/pkg/v2/proto/planpb"
+	"github.com/milvus-io/milvus/pkg/v2/proto/querypb"
 	"github.com/milvus-io/milvus/pkg/v2/util/merr"
+	"github.com/milvus-io/milvus/pkg/v2/util/typeutil"
 )
 
 func BuildSparseFieldData(field *schemapb.FieldSchema, sparseArray *schemapb.SparseFloatArray) *schemapb.FieldData {
@@ -62,3 +67,117 @@ func SetBM25Params(req *internalpb.SearchRequest, avgdl float64) error {
 	}
 	return nil
 }
+
+type (
+	Span     [2]int64
+	SpanList []Span
+)
+
+func (a SpanList) Len() int      { return len(a) }
+func (a SpanList) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
+func (a SpanList) Less(i, j int) bool {
+	if a[i][0] == a[j][0] {
+		return a[i][1] < a[j][1]
+	}
+	return a[i][0] < a[j][0]
+}
+
+// merge repeated segments
+func mergeOffsets(input SpanList) SpanList {
+	sort.Sort(input)
+	maxEndOffset := int64(-1)
+	offsets := SpanList{}
+	for _, pair := range input {
+		if pair[1] > maxEndOffset {
+			if len(offsets) == 0 || pair[0] > offsets[len(offsets)-1][1] {
+				// if start offset > max offset before,
+				// no any intersection with previous one,
+				// use all pair.
+				offsets = append(offsets, pair)
+			} else {
+				// if start offset <= max offset before,
+				// has intersection with previous one,
+				// merge two offset to one.
+				offsets[len(offsets)-1][1] = pair[1]
+			}
+			maxEndOffset = pair[1]
+		}
+	}
+	return offsets
+}
+
+func bytesOffsetToRuneOffset(text string, spans SpanList) error {
+	byteOffsetSet := typeutil.NewSet[int64]()
+	for _, span := range spans {
+		byteOffsetSet.Insert(span[0])
+		byteOffsetSet.Insert(span[1])
+	}
+	offsetMap := map[int64]int64{0: 0, int64(len(text)): int64(utf8.RuneCountInString(text))}
+
+	cnt := int64(0)
+	for i := range text {
+		if byteOffsetSet.Contain(int64(i)) {
+			offsetMap[int64(i)] = cnt
+		}
+		cnt++
+	}
+
+	// convert spans from byte offsets to rune offsets
+	for i, span := range spans {
+		startOffset, ok := offsetMap[span[0]]
+		if !ok {
+			return errors.Errorf("start offset: %d not found (text: %d bytes)", span[0], len(text))
+		}
+		endOffset, ok := offsetMap[span[1]]
+		if !ok {
+			return errors.Errorf("end offset: %d not found (text: %d bytes)", span[1], len(text))
+		}
+		spans[i][0] = startOffset
+		spans[i][1] = endOffset
+	}
+	return nil
+}
+
+func fetchFragmentsFromOffsets(text string, spans SpanList, fragmentOffset int64, fragmentSize int64, numOfFragments int64) []*querypb.HighlightFragment {
+	result := make([]*querypb.HighlightFragment, 0)
+	textRuneLen := int64(utf8.RuneCountInString(text))
+
+	var frag *querypb.HighlightFragment = nil
+	next := func(span *Span) bool {
+		startOffset := max(0, span[0]-fragmentOffset)
+		endOffset := min(max(span[1], startOffset+fragmentSize), textRuneLen)
+		if frag != nil {
+			result = append(result, frag)
+		}
+		if len(result) >= int(numOfFragments) {
+			frag = nil
+			return false
+		}
+		frag = &querypb.HighlightFragment{
+			StartOffset: startOffset,
+			EndOffset:   endOffset,
+			Offsets:     []int64{span[0], span[1]},
+		}
+		return true
+	}
+
+	for i, span := range spans {
+		if frag == nil || span[0] > frag.EndOffset {
+			if !next(&span) {
+				break
+			}
+		} else {
+			// append rune offset to fragment
+			frag.Offsets = append(frag.Offsets, spans[i][0], spans[i][1])
+			// extend fragment end offset if this span goes beyond current boundary
+			if span[1] > frag.EndOffset {
+				frag.EndOffset = span[1]
+			}
+		}
+	}
+
+	if frag != nil {
+		result = append(result, frag)
+	}
+	return result
+}

internal/querynodev2/delegator/util_test.go

@@ -0,0 +1,38 @@
+// Licensed to the LF AI & Data foundation under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+//	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package delegator
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBytesOffsetToRuneOffset(t *testing.T) {
+	// test with chinese
+	text := "你好世界" // 12 bytes, 4 runes
+	spans := SpanList{{0, 6}, {6, 12}}
+	err := bytesOffsetToRuneOffset(text, spans)
+	assert.NoError(t, err)
+	assert.Equal(t, SpanList{{0, 2}, {2, 4}}, spans)
+
+	// test with emoji
+	text = "Hello👋World" // 15 bytes, 11 runes
+	spans = SpanList{{0, 5}, {5, 9}, {9, 14}}
+	err = bytesOffsetToRuneOffset(text, spans)
+	assert.NoError(t, err)
+	assert.Equal(t, SpanList{{0, 5}, {5, 6}, {6, 11}}, spans)
+}

internal/querynodev2/services.go

@@ -1667,3 +1667,36 @@ func (node *QueryNode) DropIndex(ctx context.Context, req *querypb.DropIndexRequ
 
 	return merr.Success(), nil
 }
+
+func (node *QueryNode) GetHighlight(ctx context.Context, req *querypb.GetHighlightRequest) (*querypb.GetHighlightResponse, error) {
+	// check node healthy
+	if err := node.lifetime.Add(merr.IsHealthy); err != nil {
+		return &querypb.GetHighlightResponse{
+			Status: merr.Status(err),
+		}, nil
+	}
+	defer node.lifetime.Done()
+
+	// get delegator
+	sd, ok := node.delegators.Get(req.GetChannel())
+	if !ok {
+		err := merr.WrapErrChannelNotFound(req.GetChannel())
+		log.Warn("GetHighlight failed, failed to get shard delegator", zap.Error(err))
+		return &querypb.GetHighlightResponse{
+			Status: merr.Status(err),
+		}, nil
+	}
+
+	results, err := sd.GetHighlight(ctx, req)
+	if err != nil {
+		log.Warn("GetHighlight failed, delegator run failed", zap.Error(err))
+		return &querypb.GetHighlightResponse{
+			Status: merr.Status(err),
+		}, nil
+	}
+
+	return &querypb.GetHighlightResponse{
+		Status:  merr.Success(),
+		Results: results,
+	}, nil
+}

internal/querynodev2/services_test.go

@@ -2417,6 +2417,49 @@ func (suite *ServiceSuite) TestRunAnalyzer() {
 	})
 }
 
+func (suite *ServiceSuite) TestGetHighlight() {
+	ctx := context.Background()
+
+	suite.Run("node not healthy", func() {
+		suite.node.UpdateStateCode(commonpb.StateCode_Abnormal)
+		defer suite.node.UpdateStateCode(commonpb.StateCode_Healthy)
+
+		resp, err := suite.node.GetHighlight(ctx, &querypb.GetHighlightRequest{
+			Channel: suite.vchannel,
+			Topks:   []int64{10},
+		})
+
+		suite.NoError(err)
+		suite.Error(merr.Error(resp.GetStatus()))
+	})
+
+	suite.Run("normal case", func() {
+		delegator := &delegator.MockShardDelegator{}
+		suite.node.delegators.Insert(suite.vchannel, delegator)
+		defer suite.node.delegators.GetAndRemove(suite.vchannel)
+		delegator.EXPECT().GetHighlight(mock.Anything, mock.Anything).Return(
+			[]*querypb.HighlightResult{}, nil)
+		resp, err := suite.node.GetHighlight(ctx, &querypb.GetHighlightRequest{
+			Channel: suite.vchannel,
+			Topks:   []int64{1, 1},
+			Tasks: []*querypb.HighlightTask{
+				{
+					FieldName:     "text_field",
+					FieldId:       100,
+					Texts:         []string{"target text", "target text2", "text", "text2"},
+					AnalyzerNames: []string{"standard", "standard", "standard", "standard"},
+					SearchTextNum: 2,
+					CorpusTextNum: 2,
+				},
+			},
+		})
+
+		suite.NoError(err)
+		suite.NoError(merr.Error(resp.GetStatus()))
+		suite.NotNil(resp.Results)
+	})
+}
+
 func TestQueryNodeService(t *testing.T) {
 	wal := mock_streaming.NewMockWALAccesser(t)
 	local := mock_streaming.NewMockLocal(t)

internal/util/mock/grpc_querynode_client.go

@@ -142,6 +142,10 @@ func (m *GrpcQueryNodeClient) RunAnalyzer(ctx context.Context, in *querypb.RunAn
 	return &milvuspb.RunAnalyzerResponse{}, m.Err
 }
 
+func (m *GrpcQueryNodeClient) GetHighlight(ctx context.Context, in *querypb.GetHighlightRequest, opts ...grpc.CallOption) (*querypb.GetHighlightResponse, error) {
+	return &querypb.GetHighlightResponse{}, m.Err
+}
+
 func (m *GrpcQueryNodeClient) Close() error {
 	return m.Err
 }

internal/util/wrappers/qn_wrapper.go

@@ -160,6 +160,10 @@ func (qn *qnServerWrapper) RunAnalyzer(ctx context.Context, in *querypb.RunAnaly
 	return qn.QueryNode.RunAnalyzer(ctx, in)
 }
 
+func (qn *qnServerWrapper) GetHighlight(ctx context.Context, in *querypb.GetHighlightRequest, _ ...grpc.CallOption) (*querypb.GetHighlightResponse, error) {
+	return qn.QueryNode.GetHighlight(ctx, in)
+}
+
 func (qn *qnServerWrapper) DropIndex(ctx context.Context, in *querypb.DropIndexRequest, opts ...grpc.CallOption) (*commonpb.Status, error) {
 	return qn.QueryNode.DropIndex(ctx, in)
 }

pkg/go.mod

@@ -22,7 +22,7 @@ require (
 	github.com/jolestar/go-commons-pool/v2 v2.1.2
 	github.com/json-iterator/go v1.1.13-0.20220915233716-71ac16282d12
 	github.com/klauspost/compress v1.18.0
-	github.com/milvus-io/milvus-proto/go-api/v2 v2.6.7
+	github.com/milvus-io/milvus-proto/go-api/v2 v2.6.8-0.20251203092105-e2557263fc4c
 	github.com/minio/minio-go/v7 v7.0.73
 	github.com/panjf2000/ants/v2 v2.11.3
 	github.com/prometheus/client_golang v1.20.5

pkg/go.sum

@@ -621,8 +621,8 @@ github.com/milvus-io/cgosymbolizer v0.0.0-20250318084424-114f4050c3a6 h1:YHMFI6L
 github.com/milvus-io/cgosymbolizer v0.0.0-20250318084424-114f4050c3a6/go.mod h1:DvXTE/K/RtHehxU8/GtDs4vFtfw64jJ3PaCnFri8CRg=
 github.com/milvus-io/gorocksdb v0.0.0-20220624081344-8c5f4212846b h1:TfeY0NxYxZzUfIfYe5qYDBzt4ZYRqzUjTR6CvUzjat8=
 github.com/milvus-io/gorocksdb v0.0.0-20220624081344-8c5f4212846b/go.mod h1:iwW+9cWfIzzDseEBCCeDSN5SD16Tidvy8cwQ7ZY8Qj4=
-github.com/milvus-io/milvus-proto/go-api/v2 v2.6.7 h1:RJtZbkS5zKNIXxsqjGBUZc2SbnI4MGq+TfOfc8tJsuM=
+github.com/milvus-io/milvus-proto/go-api/v2 v2.6.8-0.20251203092105-e2557263fc4c h1:Gh02wIJEI6RUbEXwZworPBfK9BYd1SVBIDHDL8GsrCY=
-github.com/milvus-io/milvus-proto/go-api/v2 v2.6.7/go.mod h1:/6UT4zZl6awVeXLeE7UGDWZvXj3IWkRsh3mqsn0DiAs=
+github.com/milvus-io/milvus-proto/go-api/v2 v2.6.8-0.20251203092105-e2557263fc4c/go.mod h1:/6UT4zZl6awVeXLeE7UGDWZvXj3IWkRsh3mqsn0DiAs=
 github.com/minio/md5-simd v1.1.2 h1:Gdi1DZK69+ZVMoNHRXJyNcxrMA4dSxoYHZSQbirFg34=
 github.com/minio/md5-simd v1.1.2/go.mod h1:MzdKDxYpY2BT9XQFocsiZf/NKVtR7nkE4RoEpN+20RM=
 github.com/minio/minio-go/v7 v7.0.73 h1:qr2vi96Qm7kZ4v7LLebjte+MQh621fFWnv93p12htEo=

pkg/proto/query_coord.proto

@@ -172,6 +172,8 @@ service QueryNode {
     rpc UpdateSchema(UpdateSchemaRequest) returns (common.Status) {}
 
     rpc RunAnalyzer(RunAnalyzerRequest) returns(milvus.RunAnalyzerResponse){}
+    rpc GetHighlight(GetHighlightRequest) returns (GetHighlightResponse){}
+    
     rpc DropIndex(DropIndexRequest) returns (common.Status) {}
 }
 
@@ -995,6 +997,63 @@ message RunAnalyzerRequest{
     bool with_hash = 7;
 }
 
+message HighlightOptions{
+    int64 fragment_size = 1;
+    int64 fragment_offset = 2;
+    int64 num_of_fragments = 3;
+}
+
+enum HighlightQueryType{
+    TextMatch = 0;
+}
+
+message HighlightQuery{
+    HighlightQueryType type = 1;
+}
+
+// HighlightTask fetch highlight for all queries at one field
+// search_text_num/search_num == len(topks) == nq
+// corpus_text_num == sum(topks) == len(search_results)
+message HighlightTask{
+    string field_name = 1;
+    int64 field_id = 2;
+    // len(texts) = search_text_num + corpus_text_num + len(queries);
+    // text = search_text...corpus_text...query_text
+    repeated string texts = 3;
+    repeated string analyzer_names = 4; // used if field with multi-analyzer
+    
+    int64 search_text_num = 5;
+    int64 corpus_text_num = 6;
+    HighlightOptions options = 7;
+    repeated HighlightQuery queries = 8;
+}
+
+// Get Lexical highlight from delegator
+message GetHighlightRequest{
+    common.MsgBase base = 1;
+    string channel = 2;
+    repeated int64 topks = 3;
+    repeated HighlightTask tasks=4; // one task for one field
+}
+
+// start_offset and end_offset are fragment offset in the original text
+// number of offsets always be 2 * number of highlight terms in the fragment
+message HighlightFragment{      
+    int64 start_offset = 1;
+    int64 end_offset = 2;
+    // char offset of the highlight terms in the fragment
+    repeated int64 offsets = 3;
+}
+
+message HighlightResult{       
+    repeated HighlightFragment fragments = 2;
+}
+
+message GetHighlightResponse{
+    common.Status status = 1;
+    repeated HighlightResult results = 2;
+}
+
 message ListLoadedSegmentsRequest {
     common.MsgBase base = 1;
 }

pkg/proto/querypb/query_coord_grpc.pb.go

@@ -1478,6 +1478,7 @@ const (
 	QueryNode_DeleteBatch_FullMethodName          = "/milvus.proto.query.QueryNode/DeleteBatch"
 	QueryNode_UpdateSchema_FullMethodName         = "/milvus.proto.query.QueryNode/UpdateSchema"
 	QueryNode_RunAnalyzer_FullMethodName          = "/milvus.proto.query.QueryNode/RunAnalyzer"
+	QueryNode_GetHighlight_FullMethodName         = "/milvus.proto.query.QueryNode/GetHighlight"
 	QueryNode_DropIndex_FullMethodName            = "/milvus.proto.query.QueryNode/DropIndex"
 )
 
@@ -1515,6 +1516,7 @@ type QueryNodeClient interface {
 	DeleteBatch(ctx context.Context, in *DeleteBatchRequest, opts ...grpc.CallOption) (*DeleteBatchResponse, error)
 	UpdateSchema(ctx context.Context, in *UpdateSchemaRequest, opts ...grpc.CallOption) (*commonpb.Status, error)
 	RunAnalyzer(ctx context.Context, in *RunAnalyzerRequest, opts ...grpc.CallOption) (*milvuspb.RunAnalyzerResponse, error)
+	GetHighlight(ctx context.Context, in *GetHighlightRequest, opts ...grpc.CallOption) (*GetHighlightResponse, error)
 	DropIndex(ctx context.Context, in *DropIndexRequest, opts ...grpc.CallOption) (*commonpb.Status, error)
 }
 
@@ -1815,6 +1817,15 @@ func (c *queryNodeClient) RunAnalyzer(ctx context.Context, in *RunAnalyzerReques
 	return out, nil
 }
 
+func (c *queryNodeClient) GetHighlight(ctx context.Context, in *GetHighlightRequest, opts ...grpc.CallOption) (*GetHighlightResponse, error) {
+	out := new(GetHighlightResponse)
+	err := c.cc.Invoke(ctx, QueryNode_GetHighlight_FullMethodName, in, out, opts...)
+	if err != nil {
+		return nil, err
+	}
+	return out, nil
+}
+
 func (c *queryNodeClient) DropIndex(ctx context.Context, in *DropIndexRequest, opts ...grpc.CallOption) (*commonpb.Status, error) {
 	out := new(commonpb.Status)
 	err := c.cc.Invoke(ctx, QueryNode_DropIndex_FullMethodName, in, out, opts...)
@@ -1858,6 +1869,7 @@ type QueryNodeServer interface {
 	DeleteBatch(context.Context, *DeleteBatchRequest) (*DeleteBatchResponse, error)
 	UpdateSchema(context.Context, *UpdateSchemaRequest) (*commonpb.Status, error)
 	RunAnalyzer(context.Context, *RunAnalyzerRequest) (*milvuspb.RunAnalyzerResponse, error)
+	GetHighlight(context.Context, *GetHighlightRequest) (*GetHighlightResponse, error)
 	DropIndex(context.Context, *DropIndexRequest) (*commonpb.Status, error)
 }
 
@@ -1946,6 +1958,9 @@ func (UnimplementedQueryNodeServer) UpdateSchema(context.Context, *UpdateSchemaR
 func (UnimplementedQueryNodeServer) RunAnalyzer(context.Context, *RunAnalyzerRequest) (*milvuspb.RunAnalyzerResponse, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method RunAnalyzer not implemented")
 }
+func (UnimplementedQueryNodeServer) GetHighlight(context.Context, *GetHighlightRequest) (*GetHighlightResponse, error) {
+	return nil, status.Errorf(codes.Unimplemented, "method GetHighlight not implemented")
+}
 func (UnimplementedQueryNodeServer) DropIndex(context.Context, *DropIndexRequest) (*commonpb.Status, error) {
 	return nil, status.Errorf(codes.Unimplemented, "method DropIndex not implemented")
 }
@@ -2453,6 +2468,24 @@ func _QueryNode_RunAnalyzer_Handler(srv interface{}, ctx context.Context, dec fu
 	return interceptor(ctx, in, info, handler)
 }
 
+func _QueryNode_GetHighlight_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
+	in := new(GetHighlightRequest)
+	if err := dec(in); err != nil {
+		return nil, err
+	}
+	if interceptor == nil {
+		return srv.(QueryNodeServer).GetHighlight(ctx, in)
+	}
+	info := &grpc.UnaryServerInfo{
+		Server:     srv,
+		FullMethod: QueryNode_GetHighlight_FullMethodName,
+	}
+	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
+		return srv.(QueryNodeServer).GetHighlight(ctx, req.(*GetHighlightRequest))
+	}
+	return interceptor(ctx, in, info, handler)
+}
+
 func _QueryNode_DropIndex_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
 	in := new(DropIndexRequest)
 	if err := dec(in); err != nil {
@@ -2578,6 +2611,10 @@ var QueryNode_ServiceDesc = grpc.ServiceDesc{
 			MethodName: "RunAnalyzer",
 			Handler:    _QueryNode_RunAnalyzer_Handler,
 		},
+		{
+			MethodName: "GetHighlight",
+			Handler:    _QueryNode_GetHighlight_Handler,
+		},
 		{
 			MethodName: "DropIndex",
 			Handler:    _QueryNode_DropIndex_Handler,