Add WriteBuffer to provide abstraction for delta policy (#27874)

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

Makefile

@@ -430,6 +430,8 @@ generate-mockery-datanode: getdeps
 	$(INSTALL_PATH)/mockery --name=Allocator --dir=$(PWD)/internal/datanode/allocator --output=$(PWD)/internal/datanode/allocator --filename=mock_allocator.go --with-expecter --structname=MockAllocator --outpkg=allocator --inpackage
 	$(INSTALL_PATH)/mockery --name=Broker --dir=$(PWD)/internal/datanode/broker --output=$(PWD)/internal/datanode/broker/ --filename=mock_broker.go --with-expecter --structname=MockBroker --outpkg=broker --inpackage
 	$(INSTALL_PATH)/mockery --name=MetaCache --dir=$(PWD)/internal/datanode/metacache --output=$(PWD)/internal/datanode/metacache --filename=mock_meta_cache.go --with-expecter --structname=MockMetaCache --outpkg=metacache --inpackage
+	$(INSTALL_PATH)/mockery --name=SyncManager --dir=$(PWD)/internal/datanode/syncmgr --output=$(PWD)/internal/datanode/syncmgr --filename=mock_sync_manager.go --with-expecter --structname=MockSyncManager --outpkg=syncmgr --inpackage
+	$(INSTALL_PATH)/mockery --name=WriteBuffer --dir=$(PWD)/internal/datanode/writebuffer --output=$(PWD)/internal/datanode/writebuffer --filename=mock_write_buffer.go --with-expecter --structname=MockWriteBuffer --output=writebuffer --inpackage
 
 generate-mockery-metastore: getdeps
 	$(INSTALL_PATH)/mockery --name=RootCoordCatalog --dir=$(PWD)/internal/metastore --output=$(PWD)/internal/metastore/mocks --filename=mock_rootcoord_catalog.go --with-expecter --structname=RootCoordCatalog --outpkg=mocks

internal/datanode/metacache/actions.go

@@ -19,6 +19,7 @@ package metacache
 import (
 	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
 	"github.com/milvus-io/milvus-proto/go-api/v2/msgpb"
+	"github.com/milvus-io/milvus/pkg/util/typeutil"
 )
 
 type SegmentFilter func(info *SegmentInfo) bool
@@ -29,9 +30,10 @@ func WithPartitionID(partitionID int64) SegmentFilter {
 	}
 }
 
-func WithSegmentID(segmentID int64) SegmentFilter {
+func WithSegmentIDs(segmentIDs ...int64) SegmentFilter {
+	set := typeutil.NewSet[int64](segmentIDs...)
 	return func(info *SegmentInfo) bool {
-		return info.segmentID == segmentID
+		return set.Contain(info.segmentID)
 	}
 }
 

internal/datanode/metacache/actions_test.go

@@ -40,7 +40,7 @@ func (s *SegmentFilterSuite) TestFilters() {
 	s.True(filter(info))
 
 	segmentID := int64(10001)
-	filter = WithSegmentID(segmentID)
+	filter = WithSegmentIDs(segmentID)
 	info.segmentID = segmentID + 1
 	s.False(filter(info))
 	info.segmentID = segmentID

internal/datanode/metacache/meta_cache.go

@@ -23,12 +23,13 @@ import (
 	"go.uber.org/zap"
 
 	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+	"github.com/milvus-io/milvus-proto/go-api/v2/msgpb"
 	"github.com/milvus-io/milvus/internal/proto/datapb"
 	"github.com/milvus-io/milvus/pkg/log"
 )
 
 type MetaCache interface {
-	NewSegment(segmentID, partitionID int64)
+	NewSegment(segmentID, partitionID int64, startPos *msgpb.MsgPosition, actions ...SegmentAction)
 	UpdateSegments(action SegmentAction, filters ...SegmentFilter)
 	CompactSegments(newSegmentID, partitionID int64, oldSegmentIDs ...int64)
 	GetSegmentsBy(filters ...SegmentFilter) []*SegmentInfo
@@ -67,17 +68,21 @@ func (c *metaCacheImpl) init(vchannel *datapb.VchannelInfo, factory PkStatsFacto
 	}
 }
 
-func (c *metaCacheImpl) NewSegment(segmentID, partitionID int64) {
+func (c *metaCacheImpl) NewSegment(segmentID, partitionID int64, startPos *msgpb.MsgPosition, actions ...SegmentAction) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
 	if _, ok := c.segmentInfos[segmentID]; !ok {
-		c.segmentInfos[segmentID] = &SegmentInfo{
+		info := &SegmentInfo{
 			segmentID:        segmentID,
 			partitionID:      partitionID,
 			state:            commonpb.SegmentState_Growing,
 			startPosRecorded: false,
 		}
+		for _, action := range actions {
+			action(info)
+		}
+		c.segmentInfos[segmentID] = info
 	}
 }
 

internal/datanode/metacache/meta_cache_test.go

@@ -81,7 +81,7 @@ func (s *MetaCacheSuite) SetupTest() {
 
 func (s *MetaCacheSuite) TestNewSegment() {
 	for i, seg := range s.newSegments {
-		s.cache.NewSegment(seg, s.partitionIDs[i])
+		s.cache.NewSegment(seg, s.partitionIDs[i], nil, UpdateNumOfRows(100))
 	}
 
 	for id, partitionID := range s.partitionIDs {
@@ -110,8 +110,8 @@ func (s *MetaCacheSuite) TestCompactSegments() {
 }
 
 func (s *MetaCacheSuite) TestUpdateSegments() {
-	s.cache.UpdateSegments(UpdateState(commonpb.SegmentState_Flushed), WithSegmentID(5))
+	s.cache.UpdateSegments(UpdateState(commonpb.SegmentState_Flushed), WithSegmentIDs(5))
-	segments := s.cache.GetSegmentsBy(WithSegmentID(5))
+	segments := s.cache.GetSegmentsBy(WithSegmentIDs(5))
 	s.Require().Equal(1, len(segments))
 	segment := segments[0]
 	s.Equal(commonpb.SegmentState_Flushed, segment.State())

internal/datanode/metacache/mock_meta_cache.go

@@ -2,7 +2,10 @@
 
 package metacache
 
-import mock "github.com/stretchr/testify/mock"
+import (
+	msgpb "github.com/milvus-io/milvus-proto/go-api/v2/msgpb"
+	mock "github.com/stretchr/testify/mock"
+)
 
 // MockMetaCache is an autogenerated mock type for the MetaCache type
 type MockMetaCache struct {
@@ -180,9 +183,16 @@ func (_c *MockMetaCache_GetSegmentsBy_Call) RunAndReturn(run func(...SegmentFilt
 	return _c
 }
 
-// NewSegment provides a mock function with given fields: segmentID, partitionID
+// NewSegment provides a mock function with given fields: segmentID, partitionID, startPos, actions
-func (_m *MockMetaCache) NewSegment(segmentID int64, partitionID int64) {
+func (_m *MockMetaCache) NewSegment(segmentID int64, partitionID int64, startPos *msgpb.MsgPosition, actions ...SegmentAction) {
-	_m.Called(segmentID, partitionID)
+	_va := make([]interface{}, len(actions))
+	for _i := range actions {
+		_va[_i] = actions[_i]
+	}
+	var _ca []interface{}
+	_ca = append(_ca, segmentID, partitionID, startPos)
+	_ca = append(_ca, _va...)
+	_m.Called(_ca...)
 }
 
 // MockMetaCache_NewSegment_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'NewSegment'
@@ -193,13 +203,22 @@ type MockMetaCache_NewSegment_Call struct {
 // NewSegment is a helper method to define mock.On call
 //   - segmentID int64
 //   - partitionID int64
-func (_e *MockMetaCache_Expecter) NewSegment(segmentID interface{}, partitionID interface{}) *MockMetaCache_NewSegment_Call {
+//   - startPos *msgpb.MsgPosition
-	return &MockMetaCache_NewSegment_Call{Call: _e.mock.On("NewSegment", segmentID, partitionID)}
+//   - actions ...SegmentAction
+func (_e *MockMetaCache_Expecter) NewSegment(segmentID interface{}, partitionID interface{}, startPos interface{}, actions ...interface{}) *MockMetaCache_NewSegment_Call {
+	return &MockMetaCache_NewSegment_Call{Call: _e.mock.On("NewSegment",
+		append([]interface{}{segmentID, partitionID, startPos}, actions...)...)}
 }
 
-func (_c *MockMetaCache_NewSegment_Call) Run(run func(segmentID int64, partitionID int64)) *MockMetaCache_NewSegment_Call {
+func (_c *MockMetaCache_NewSegment_Call) Run(run func(segmentID int64, partitionID int64, startPos *msgpb.MsgPosition, actions ...SegmentAction)) *MockMetaCache_NewSegment_Call {
 	_c.Call.Run(func(args mock.Arguments) {
-		run(args[0].(int64), args[1].(int64))
+		variadicArgs := make([]SegmentAction, len(args)-3)
+		for i, a := range args[3:] {
+			if a != nil {
+				variadicArgs[i] = a.(SegmentAction)
+			}
+		}
+		run(args[0].(int64), args[1].(int64), args[2].(*msgpb.MsgPosition), variadicArgs...)
 	})
 	return _c
 }
@@ -209,7 +228,7 @@ func (_c *MockMetaCache_NewSegment_Call) Return() *MockMetaCache_NewSegment_Call
 	return _c
 }
 
-func (_c *MockMetaCache_NewSegment_Call) RunAndReturn(run func(int64, int64)) *MockMetaCache_NewSegment_Call {
+func (_c *MockMetaCache_NewSegment_Call) RunAndReturn(run func(int64, int64, *msgpb.MsgPosition, ...SegmentAction)) *MockMetaCache_NewSegment_Call {
 	_c.Call.Return(run)
 	return _c
 }

internal/datanode/metacache/segment.go

@@ -67,6 +67,10 @@ func (s *SegmentInfo) CompactTo() int64 {
 	return s.compactTo
 }
 
+func (s *SegmentInfo) GetBloomFilterSet() *BloomFilterSet {
+	return s.bfs
+}
+
 func (s *SegmentInfo) Clone() *SegmentInfo {
 	return &SegmentInfo{
 		segmentID:        s.segmentID,

internal/datanode/syncmgr/meta_writer.go

@@ -51,7 +51,7 @@ func (b *brokerMetaWriter) UpdateSync(pack *SyncTask) error {
 	deltaInfos[0] = &datapb.FieldBinlog{Binlogs: []*datapb.Binlog{pack.deltaBinlog}}
 
 	// only current segment checkpoint info,
-	segments := pack.metacache.GetSegmentsBy(metacache.WithSegmentID(pack.segmentID))
+	segments := pack.metacache.GetSegmentsBy(metacache.WithSegmentIDs(pack.segmentID))
 	if len(segments) == 0 {
 		return merr.WrapErrSegmentNotFound(pack.segmentID)
 	}
@@ -96,8 +96,8 @@ func (b *brokerMetaWriter) UpdateSync(pack *SyncTask) error {
 
 		StartPositions: startPos,
 		Flushed:        pack.isFlush,
-		//		Dropped:        pack.option.isDrop,
+		Dropped:        pack.isDrop,
-		Channel: pack.channelName,
+		Channel:        pack.channelName,
 	}
 	err := retry.Do(context.Background(), func() error {
 		err := b.broker.SaveBinlogPaths(context.Background(), req)

internal/datanode/syncmgr/mock_sync_manager.go

@@ -0,0 +1,145 @@
+// Code generated by mockery v2.32.4. DO NOT EDIT.
+
+package syncmgr
+
+import (
+	context "context"
+
+	mock "github.com/stretchr/testify/mock"
+)
+
+// MockSyncManager is an autogenerated mock type for the SyncManager type
+type MockSyncManager struct {
+	mock.Mock
+}
+
+type MockSyncManager_Expecter struct {
+	mock *mock.Mock
+}
+
+func (_m *MockSyncManager) EXPECT() *MockSyncManager_Expecter {
+	return &MockSyncManager_Expecter{mock: &_m.Mock}
+}
+
+// Block provides a mock function with given fields: segmentID
+func (_m *MockSyncManager) Block(segmentID int64) {
+	_m.Called(segmentID)
+}
+
+// MockSyncManager_Block_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'Block'
+type MockSyncManager_Block_Call struct {
+	*mock.Call
+}
+
+// Block is a helper method to define mock.On call
+//   - segmentID int64
+func (_e *MockSyncManager_Expecter) Block(segmentID interface{}) *MockSyncManager_Block_Call {
+	return &MockSyncManager_Block_Call{Call: _e.mock.On("Block", segmentID)}
+}
+
+func (_c *MockSyncManager_Block_Call) Run(run func(segmentID int64)) *MockSyncManager_Block_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run(args[0].(int64))
+	})
+	return _c
+}
+
+func (_c *MockSyncManager_Block_Call) Return() *MockSyncManager_Block_Call {
+	_c.Call.Return()
+	return _c
+}
+
+func (_c *MockSyncManager_Block_Call) RunAndReturn(run func(int64)) *MockSyncManager_Block_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
+// SyncData provides a mock function with given fields: ctx, task
+func (_m *MockSyncManager) SyncData(ctx context.Context, task *SyncTask) error {
+	ret := _m.Called(ctx, task)
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func(context.Context, *SyncTask) error); ok {
+		r0 = rf(ctx, task)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
+// MockSyncManager_SyncData_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'SyncData'
+type MockSyncManager_SyncData_Call struct {
+	*mock.Call
+}
+
+// SyncData is a helper method to define mock.On call
+//   - ctx context.Context
+//   - task *SyncTask
+func (_e *MockSyncManager_Expecter) SyncData(ctx interface{}, task interface{}) *MockSyncManager_SyncData_Call {
+	return &MockSyncManager_SyncData_Call{Call: _e.mock.On("SyncData", ctx, task)}
+}
+
+func (_c *MockSyncManager_SyncData_Call) Run(run func(ctx context.Context, task *SyncTask)) *MockSyncManager_SyncData_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run(args[0].(context.Context), args[1].(*SyncTask))
+	})
+	return _c
+}
+
+func (_c *MockSyncManager_SyncData_Call) Return(_a0 error) *MockSyncManager_SyncData_Call {
+	_c.Call.Return(_a0)
+	return _c
+}
+
+func (_c *MockSyncManager_SyncData_Call) RunAndReturn(run func(context.Context, *SyncTask) error) *MockSyncManager_SyncData_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
+// Unblock provides a mock function with given fields: segmentID
+func (_m *MockSyncManager) Unblock(segmentID int64) {
+	_m.Called(segmentID)
+}
+
+// MockSyncManager_Unblock_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'Unblock'
+type MockSyncManager_Unblock_Call struct {
+	*mock.Call
+}
+
+// Unblock is a helper method to define mock.On call
+//   - segmentID int64
+func (_e *MockSyncManager_Expecter) Unblock(segmentID interface{}) *MockSyncManager_Unblock_Call {
+	return &MockSyncManager_Unblock_Call{Call: _e.mock.On("Unblock", segmentID)}
+}
+
+func (_c *MockSyncManager_Unblock_Call) Run(run func(segmentID int64)) *MockSyncManager_Unblock_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run(args[0].(int64))
+	})
+	return _c
+}
+
+func (_c *MockSyncManager_Unblock_Call) Return() *MockSyncManager_Unblock_Call {
+	_c.Call.Return()
+	return _c
+}
+
+func (_c *MockSyncManager_Unblock_Call) RunAndReturn(run func(int64)) *MockSyncManager_Unblock_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
+// NewMockSyncManager creates a new instance of MockSyncManager. It also registers a testing interface on the mock and a cleanup function to assert the mocks expectations.
+// The first argument is typically a *testing.T value.
+func NewMockSyncManager(t interface {
+	mock.TestingT
+	Cleanup(func())
+}) *MockSyncManager {
+	mock := &MockSyncManager{}
+	mock.Mock.Test(t)
+
+	t.Cleanup(func() { mock.AssertExpectations(t) })
+
+	return mock
+}

internal/datanode/syncmgr/options.go

@@ -80,6 +80,11 @@ func (t *SyncTask) WithFlush() *SyncTask {
 	return t
 }
 
+func (t *SyncTask) WithDrop() *SyncTask {
+	t.isDrop = true
+	return t
+}
+
 func (t *SyncTask) WithMetaCache(metacache metacache.MetaCache) *SyncTask {
 	t.metacache = metacache
 	return t

internal/datanode/syncmgr/task.go

@@ -41,6 +41,7 @@ type SyncTask struct {
 	tsTo   typeutil.Timestamp
 
 	isFlush bool
+	isDrop  bool
 
 	metacache  metacache.MetaCache
 	metaWriter MetaWriter
@@ -75,7 +76,7 @@ func (t *SyncTask) Run() error {
 	log := t.getLogger()
 	var err error
 
-	infos := t.metacache.GetSegmentsBy(metacache.WithSegmentID(t.segmentID))
+	infos := t.metacache.GetSegmentsBy(metacache.WithSegmentIDs(t.segmentID))
 	if len(infos) == 0 {
 		log.Warn("failed to sync data, segment not found in metacache")
 		t.handleError(err)
@@ -245,7 +246,7 @@ func (t *SyncTask) serializeSinglePkStats(fieldID int64, stats *storage.PrimaryK
 }
 
 func (t *SyncTask) serializeMergedPkStats(fieldID int64, stats *storage.PrimaryKeyStats, rowNum int64) error {
-	segments := t.metacache.GetSegmentsBy(metacache.WithSegmentID(t.segmentID))
+	segments := t.metacache.GetSegmentsBy(metacache.WithSegmentIDs(t.segmentID))
 	var statsList []*storage.PrimaryKeyStats
 	var oldRowNum int64
 	for _, segment := range segments {

internal/datanode/syncmgr/task_test.go

@@ -201,6 +201,7 @@ func (s *SyncTaskSuite) TestRunNormal() {
 		task := s.getSuiteSyncTask()
 		task.WithInsertData(s.getInsertBuffer()).WithDeleteData(s.getDeleteBuffer())
 		task.WithFlush()
+		task.WithDrop()
 		task.WithMetaWriter(BrokerMetaWriter(s.broker))
 		task.WithCheckpoint(&msgpb.MsgPosition{
 			ChannelName: s.channelName,

internal/datanode/writebuffer/bf_write_buffer.go

@@ -0,0 +1,73 @@
+package writebuffer
+
+import (
+	"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/datanode/metacache"
+	"github.com/milvus-io/milvus/internal/datanode/syncmgr"
+	"github.com/milvus-io/milvus/internal/storage"
+	"github.com/milvus-io/milvus/pkg/mq/msgstream"
+	"github.com/milvus-io/milvus/pkg/util/typeutil"
+)
+
+type bfWriteBuffer struct {
+	*writeBufferBase
+
+	syncMgr   syncmgr.SyncManager
+	metacache metacache.MetaCache
+}
+
+func NewBFWriteBuffer(sch *schemapb.CollectionSchema, metacache metacache.MetaCache, syncMgr syncmgr.SyncManager, option *writeBufferOption) (WriteBuffer, error) {
+	return &bfWriteBuffer{
+		writeBufferBase: newWriteBufferBase(sch, metacache, syncMgr, option),
+		syncMgr:         syncMgr,
+	}, nil
+}
+
+func (wb *bfWriteBuffer) BufferData(insertMsgs []*msgstream.InsertMsg, deleteMsgs []*msgstream.DeleteMsg, startPos, endPos *msgpb.MsgPosition) error {
+	wb.mut.Lock()
+	defer wb.mut.Unlock()
+
+	// process insert msgs
+	pkData, err := wb.bufferInsert(insertMsgs, startPos, endPos)
+	if err != nil {
+		return err
+	}
+
+	// update pk oracle
+	for segmentID, dataList := range pkData {
+		segments := wb.metaCache.GetSegmentsBy(metacache.WithSegmentIDs(segmentID))
+		for _, segment := range segments {
+			for _, fieldData := range dataList {
+				err := segment.GetBloomFilterSet().UpdatePKRange(fieldData)
+				if err != nil {
+					return err
+				}
+			}
+		}
+	}
+
+	// distribute delete msg
+	for _, delMsg := range deleteMsgs {
+		pks := storage.ParseIDs2PrimaryKeys(delMsg.GetPrimaryKeys())
+		segments := wb.metaCache.GetSegmentsBy(metacache.WithPartitionID(delMsg.PartitionID))
+		for _, segment := range segments {
+			var deletePks []storage.PrimaryKey
+			var deleteTss []typeutil.Timestamp
+			for idx, pk := range pks {
+				if segment.GetBloomFilterSet().PkExists(pk) {
+					deletePks = append(deletePks, pk)
+					deleteTss = append(deleteTss, delMsg.GetTimestamps()[idx])
+				}
+			}
+			if len(deletePks) > 0 {
+				wb.bufferDelete(segment.SegmentID(), deletePks, deleteTss, startPos, endPos)
+			}
+		}
+	}
+
+	// update buffer last checkpoint
+	wb.checkpoint = endPos
+
+	return wb.triggerAutoSync()
+}

internal/datanode/writebuffer/bf_write_buffer_test.go

@@ -0,0 +1,182 @@
+package writebuffer
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/samber/lo"
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+	"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/datanode/broker"
+	"github.com/milvus-io/milvus/internal/datanode/metacache"
+	"github.com/milvus-io/milvus/internal/datanode/syncmgr"
+	"github.com/milvus-io/milvus/internal/proto/datapb"
+	"github.com/milvus-io/milvus/internal/storage"
+	"github.com/milvus-io/milvus/pkg/common"
+	"github.com/milvus-io/milvus/pkg/mq/msgstream"
+	"github.com/milvus-io/milvus/pkg/util/paramtable"
+	"github.com/milvus-io/milvus/pkg/util/tsoutil"
+)
+
+type BFWriteBufferSuite struct {
+	suite.Suite
+	collSchema *schemapb.CollectionSchema
+	syncMgr    *syncmgr.MockSyncManager
+	metacache  *metacache.MockMetaCache
+	broker     *broker.MockBroker
+}
+
+func (s *BFWriteBufferSuite) SetupSuite() {
+	paramtable.Get().Init(paramtable.NewBaseTable())
+	s.collSchema = &schemapb.CollectionSchema{
+		Name: "test_collection",
+		Fields: []*schemapb.FieldSchema{
+			{
+				FieldID: common.RowIDField, Name: common.RowIDFieldName, DataType: schemapb.DataType_Int64,
+			},
+			{
+				FieldID: common.TimeStampField, Name: common.TimeStampFieldName, DataType: schemapb.DataType_Int64,
+			},
+			{
+				FieldID: 100, Name: "pk", DataType: schemapb.DataType_Int64, IsPrimaryKey: true,
+			},
+			{
+				FieldID: 101, Name: "vector", DataType: schemapb.DataType_FloatVector,
+				TypeParams: []*commonpb.KeyValuePair{
+					{Key: common.DimKey, Value: "128"},
+				},
+			},
+		},
+	}
+}
+
+func (s *BFWriteBufferSuite) composeInsertMsg(segmentID int64, rowCount int, dim int) ([]int64, *msgstream.InsertMsg) {
+	tss := lo.RepeatBy(rowCount, func(idx int) int64 { return int64(tsoutil.ComposeTSByTime(time.Now(), int64(idx))) })
+	vectors := lo.RepeatBy(rowCount, func(_ int) []float32 {
+		return lo.RepeatBy(dim, func(_ int) float32 { return rand.Float32() })
+	})
+	flatten := lo.Flatten(vectors)
+	return tss, &msgstream.InsertMsg{
+		InsertRequest: msgpb.InsertRequest{
+			SegmentID:  segmentID,
+			Version:    msgpb.InsertDataVersion_ColumnBased,
+			RowIDs:     tss,
+			Timestamps: lo.Map(tss, func(id int64, _ int) uint64 { return uint64(id) }),
+			FieldsData: []*schemapb.FieldData{
+				{
+					FieldId: common.RowIDField, FieldName: common.RowIDFieldName, Type: schemapb.DataType_Int64,
+					Field: &schemapb.FieldData_Scalars{
+						Scalars: &schemapb.ScalarField{
+							Data: &schemapb.ScalarField_LongData{
+								LongData: &schemapb.LongArray{
+									Data: tss,
+								},
+							},
+						},
+					},
+				},
+				{
+					FieldId: common.TimeStampField, FieldName: common.TimeStampFieldName, Type: schemapb.DataType_Int64,
+					Field: &schemapb.FieldData_Scalars{
+						Scalars: &schemapb.ScalarField{
+							Data: &schemapb.ScalarField_LongData{
+								LongData: &schemapb.LongArray{
+									Data: tss,
+								},
+							},
+						},
+					},
+				},
+				{
+					FieldId: common.StartOfUserFieldID, FieldName: "pk", Type: schemapb.DataType_Int64,
+					Field: &schemapb.FieldData_Scalars{
+						Scalars: &schemapb.ScalarField{
+							Data: &schemapb.ScalarField_LongData{
+								LongData: &schemapb.LongArray{
+									Data: tss,
+								},
+							},
+						},
+					},
+				},
+				{
+					FieldId: common.StartOfUserFieldID + 1, FieldName: "vector", Type: schemapb.DataType_FloatVector,
+					Field: &schemapb.FieldData_Vectors{
+						Vectors: &schemapb.VectorField{
+							Dim: int64(dim),
+							Data: &schemapb.VectorField_FloatVector{
+								FloatVector: &schemapb.FloatArray{
+									Data: flatten,
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+}
+
+func (s *BFWriteBufferSuite) composeDeleteMsg(pks []storage.PrimaryKey) *msgstream.DeleteMsg {
+	delMsg := &msgstream.DeleteMsg{
+		DeleteRequest: msgpb.DeleteRequest{
+			PrimaryKeys: storage.ParsePrimaryKeys2IDs(pks),
+			Timestamps:  lo.RepeatBy(len(pks), func(idx int) uint64 { return tsoutil.ComposeTSByTime(time.Now(), int64(idx)) }),
+		},
+	}
+	return delMsg
+}
+
+func (s *BFWriteBufferSuite) SetupTest() {
+	s.syncMgr = syncmgr.NewMockSyncManager(s.T())
+	s.metacache = metacache.NewMockMetaCache(s.T())
+	s.broker = broker.NewMockBroker(s.T())
+}
+
+func (s *BFWriteBufferSuite) TestBufferData() {
+	wb, err := NewBFWriteBuffer(s.collSchema, s.metacache, s.syncMgr, &writeBufferOption{})
+	s.NoError(err)
+
+	seg := metacache.NewSegmentInfo(&datapb.SegmentInfo{ID: 1000}, metacache.NewBloomFilterSet())
+	s.metacache.EXPECT().GetSegmentsBy(mock.Anything).Return([]*metacache.SegmentInfo{seg})
+
+	pks, msg := s.composeInsertMsg(1000, 10, 128)
+	delMsg := s.composeDeleteMsg(lo.Map(pks, func(id int64, _ int) storage.PrimaryKey { return storage.NewInt64PrimaryKey(id) }))
+
+	err = wb.BufferData([]*msgstream.InsertMsg{msg}, []*msgstream.DeleteMsg{delMsg}, &msgpb.MsgPosition{Timestamp: 100}, &msgpb.MsgPosition{Timestamp: 200})
+	s.NoError(err)
+}
+
+func (s *BFWriteBufferSuite) TestAutoSync() {
+	paramtable.Get().Save(paramtable.Get().DataNodeCfg.FlushInsertBufferSize.Key, "1")
+
+	wb, err := NewBFWriteBuffer(s.collSchema, s.metacache, s.syncMgr, &writeBufferOption{
+		syncPolicies: []SyncPolicy{
+			SyncFullBuffer,
+			GetSyncStaleBufferPolicy(paramtable.Get().DataNodeCfg.SyncPeriod.GetAsDuration(time.Second)),
+			GetFlushingSegmentsPolicy(s.metacache),
+		},
+	})
+	s.NoError(err)
+
+	seg := metacache.NewSegmentInfo(&datapb.SegmentInfo{ID: 1000}, metacache.NewBloomFilterSet())
+	s.metacache.EXPECT().GetSegmentsBy(mock.Anything).Return([]*metacache.SegmentInfo{seg})
+	s.metacache.EXPECT().GetSegmentIDsBy(mock.Anything).Return([]int64{1002}) // mock flushing
+	s.metacache.EXPECT().UpdateSegments(mock.Anything, mock.Anything, mock.Anything).Return()
+	s.syncMgr.EXPECT().SyncData(mock.Anything, mock.Anything).Return(nil).Twice()
+
+	pks, msg := s.composeInsertMsg(1000, 10, 128)
+	delMsg := s.composeDeleteMsg(lo.Map(pks, func(id int64, _ int) storage.PrimaryKey { return storage.NewInt64PrimaryKey(id) }))
+
+	err = wb.BufferData([]*msgstream.InsertMsg{msg}, []*msgstream.DeleteMsg{delMsg}, &msgpb.MsgPosition{Timestamp: 100}, &msgpb.MsgPosition{Timestamp: 200})
+	s.NoError(err)
+}
+
+func TestBFWriteBuffer(t *testing.T) {
+	suite.Run(t, new(BFWriteBufferSuite))
+}

internal/datanode/writebuffer/delta_buffer.go

@@ -0,0 +1,80 @@
+package writebuffer
+
+import (
+	"math"
+
+	"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/storage"
+	"github.com/milvus-io/milvus/pkg/util/paramtable"
+	"github.com/milvus-io/milvus/pkg/util/typeutil"
+)
+
+type DeltaBuffer struct {
+	BufferBase
+
+	buffer *storage.DeleteData
+}
+
+func NewDeltaBuffer() *DeltaBuffer {
+	return &DeltaBuffer{
+		BufferBase: BufferBase{
+			rowLimit:      noLimit,
+			sizeLimit:     paramtable.Get().DataNodeCfg.FlushDeleteBufferBytes.GetAsInt64(),
+			TimestampFrom: math.MaxUint64,
+			TimestampTo:   0,
+		},
+		buffer: &storage.DeleteData{},
+	}
+}
+
+func (ib *DeltaBuffer) getTimestampRange(tss []typeutil.Timestamp) TimeRange {
+	tr := TimeRange{
+		timestampMin: math.MaxUint64,
+		timestampMax: 0,
+	}
+
+	for _, data := range tss {
+		if data < tr.timestampMin {
+			tr.timestampMin = data
+		}
+		if data > tr.timestampMax {
+			tr.timestampMax = data
+		}
+	}
+	return tr
+}
+
+func (db *DeltaBuffer) Renew() *storage.DeleteData {
+	if db.IsEmpty() {
+		return nil
+	}
+	result := db.buffer
+	db.BufferBase.rows = 0
+	db.BufferBase.TimestampFrom = math.MaxUint64
+	db.BufferBase.TimestampTo = 0
+
+	return result
+}
+
+func (db *DeltaBuffer) Buffer(pks []storage.PrimaryKey, tss []typeutil.Timestamp, startPos, endPos *msgpb.MsgPosition) (bufSize int64) {
+	rowCount := len(pks)
+
+	for i := 0; i < rowCount; i++ {
+		db.buffer.Append(pks[i], tss[i])
+
+		switch pks[i].Type() {
+		case schemapb.DataType_Int64:
+			bufSize += 8
+		case schemapb.DataType_VarChar:
+			varCharPk := pks[i].(*storage.VarCharPrimaryKey)
+			bufSize += int64(len(varCharPk.Value))
+		}
+		// accumulate buf size for timestamp, which is 8 bytes
+		bufSize += 8
+	}
+
+	db.UpdateStatistics(int64(rowCount), bufSize, db.getTimestampRange(tss), startPos, endPos)
+
+	return bufSize
+}

internal/datanode/writebuffer/delta_buffer_test.go

@@ -0,0 +1,66 @@
+package writebuffer
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/samber/lo"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/msgpb"
+	"github.com/milvus-io/milvus/internal/storage"
+	"github.com/milvus-io/milvus/pkg/util/tsoutil"
+)
+
+type DeltaBufferSuite struct {
+	suite.Suite
+}
+
+func (s *DeltaBufferSuite) TestBuffer() {
+	s.Run("int64_pk", func() {
+		deltaBuffer := NewDeltaBuffer()
+
+		tss := lo.RepeatBy(100, func(idx int) uint64 { return tsoutil.ComposeTSByTime(time.Now(), int64(idx)) })
+		pks := lo.Map(tss, func(ts uint64, _ int) storage.PrimaryKey { return storage.NewInt64PrimaryKey(int64(ts)) })
+
+		memSize := deltaBuffer.Buffer(pks, tss, &msgpb.MsgPosition{Timestamp: 100}, &msgpb.MsgPosition{Timestamp: 200})
+		s.EqualValues(100*8*2, memSize)
+	})
+
+	s.Run("string_pk", func() {
+		deltaBuffer := NewDeltaBuffer()
+
+		tss := lo.RepeatBy(100, func(idx int) uint64 { return tsoutil.ComposeTSByTime(time.Now(), int64(idx)) })
+		pks := lo.Map(tss, func(ts uint64, idx int) storage.PrimaryKey {
+			return storage.NewVarCharPrimaryKey(fmt.Sprintf("%03d", idx))
+		})
+
+		memSize := deltaBuffer.Buffer(pks, tss, &msgpb.MsgPosition{Timestamp: 100}, &msgpb.MsgPosition{Timestamp: 200})
+		s.EqualValues(100*8+100*3, memSize)
+	})
+}
+
+func (s *DeltaBufferSuite) TestRenew() {
+	deltaBuffer := NewDeltaBuffer()
+
+	result := deltaBuffer.Renew()
+	s.Nil(result)
+	s.True(deltaBuffer.IsEmpty())
+
+	tss := lo.RepeatBy(100, func(idx int) uint64 { return tsoutil.ComposeTSByTime(time.Now(), int64(idx)) })
+	pks := lo.Map(tss, func(ts uint64, _ int) storage.PrimaryKey { return storage.NewInt64PrimaryKey(int64(ts)) })
+
+	deltaBuffer.Buffer(pks, tss, &msgpb.MsgPosition{Timestamp: 100}, &msgpb.MsgPosition{Timestamp: 200})
+
+	result = deltaBuffer.Renew()
+	s.NotNil(result)
+	s.True(deltaBuffer.IsEmpty())
+
+	s.ElementsMatch(tss, result.Tss)
+	s.ElementsMatch(pks, result.Pks)
+}
+
+func TestDeltaBuffer(t *testing.T) {
+	suite.Run(t, new(DeltaBufferSuite))
+}

internal/datanode/writebuffer/insert_buffer.go

@@ -0,0 +1,171 @@
+package writebuffer
+
+import (
+	"math"
+
+	"github.com/cockroachdb/errors"
+	"go.uber.org/zap"
+
+	"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/storage"
+	"github.com/milvus-io/milvus/pkg/log"
+	"github.com/milvus-io/milvus/pkg/mq/msgstream"
+	"github.com/milvus-io/milvus/pkg/util/merr"
+	"github.com/milvus-io/milvus/pkg/util/paramtable"
+	"github.com/milvus-io/milvus/pkg/util/typeutil"
+)
+
+const (
+	noLimit int64 = -1
+)
+
+type BufferBase struct {
+	rows      int64
+	rowLimit  int64
+	size      int64
+	sizeLimit int64
+
+	TimestampFrom typeutil.Timestamp
+	TimestampTo   typeutil.Timestamp
+
+	startPos *msgpb.MsgPosition
+	endPos   *msgpb.MsgPosition
+}
+
+func (b *BufferBase) UpdateStatistics(entryNum, size int64, tr TimeRange, startPos, endPos *msgpb.MsgPosition) {
+	b.rows += entryNum
+	b.size += size
+
+	if tr.timestampMin < b.TimestampFrom {
+		b.TimestampFrom = tr.timestampMin
+	}
+	if tr.timestampMax > b.TimestampTo {
+		b.TimestampTo = tr.timestampMax
+	}
+
+	if b.startPos == nil || startPos.Timestamp < b.startPos.Timestamp {
+		b.startPos = startPos
+	}
+	if b.endPos == nil || endPos.Timestamp > b.endPos.Timestamp {
+		b.endPos = endPos
+	}
+}
+
+func (b *BufferBase) IsFull() bool {
+	return (b.rowLimit != noLimit && b.rows >= b.rowLimit) ||
+		(b.sizeLimit != noLimit && b.size >= b.sizeLimit)
+}
+
+func (b *BufferBase) IsEmpty() bool {
+	return b.rows == 0
+}
+
+func (b *BufferBase) MinTimestamp() typeutil.Timestamp {
+	if b.startPos == nil {
+		return math.MaxUint64
+	}
+	return b.startPos.GetTimestamp()
+}
+
+type InsertBuffer struct {
+	BufferBase
+	collSchema *schemapb.CollectionSchema
+
+	buffer *storage.InsertData
+}
+
+func NewInsertBuffer(sch *schemapb.CollectionSchema) (*InsertBuffer, error) {
+	size, err := typeutil.EstimateSizePerRecord(sch)
+	if err != nil {
+		log.Warn("failed to estimate size per record", zap.Error(err))
+		return nil, err
+	}
+
+	if size == 0 {
+		return nil, errors.New("Invalid schema")
+	}
+	buffer, err := storage.NewInsertData(sch)
+	if err != nil {
+		return nil, err
+	}
+	limit := paramtable.Get().DataNodeCfg.FlushInsertBufferSize.GetAsInt64() / int64(size)
+	if paramtable.Get().DataNodeCfg.FlushInsertBufferSize.GetAsInt64()%int64(size) != 0 {
+		limit++
+	}
+
+	return &InsertBuffer{
+		BufferBase: BufferBase{
+			rowLimit:      limit,
+			sizeLimit:     noLimit,
+			TimestampFrom: math.MaxUint64,
+			TimestampTo:   0,
+		},
+		collSchema: sch,
+		buffer:     buffer,
+	}, nil
+}
+
+func (ib *InsertBuffer) Renew() *storage.InsertData {
+	if ib.IsEmpty() {
+		return nil
+	}
+	result := ib.buffer
+
+	// no error since validated in constructor
+	ib.buffer, _ = storage.NewInsertData(ib.collSchema)
+	ib.BufferBase.rows = 0
+	ib.BufferBase.TimestampFrom = math.MaxUint64
+	ib.BufferBase.TimestampTo = 0
+
+	return result
+}
+
+func (ib *InsertBuffer) Buffer(msgs []*msgstream.InsertMsg, startPos, endPos *msgpb.MsgPosition) ([]storage.FieldData, error) {
+	pkData := make([]storage.FieldData, 0, len(msgs))
+	for _, msg := range msgs {
+		tmpBuffer, err := storage.InsertMsgToInsertData(msg, ib.collSchema)
+		if err != nil {
+			log.Warn("failed to transfer insert msg to insert data", zap.Error(err))
+			return nil, err
+		}
+
+		pkFieldData, err := storage.GetPkFromInsertData(ib.collSchema, tmpBuffer)
+		if err != nil {
+			return nil, err
+		}
+		if pkFieldData.RowNum() != tmpBuffer.GetRowNum() {
+			return nil, merr.WrapErrServiceInternal("pk column row num not match")
+		}
+		pkData = append(pkData, pkFieldData)
+
+		storage.MergeInsertData(ib.buffer, tmpBuffer)
+
+		tsData, err := storage.GetTimestampFromInsertData(tmpBuffer)
+		if err != nil {
+			log.Warn("no timestamp field found in insert msg", zap.Error(err))
+			return nil, err
+		}
+
+		// update buffer size
+		ib.UpdateStatistics(int64(tmpBuffer.GetRowNum()), 0, ib.getTimestampRange(tsData), startPos, endPos)
+	}
+	return pkData, nil
+}
+
+func (ib *InsertBuffer) getTimestampRange(tsData *storage.Int64FieldData) TimeRange {
+	tr := TimeRange{
+		timestampMin: math.MaxUint64,
+		timestampMax: 0,
+	}
+
+	for _, data := range tsData.Data {
+		if uint64(data) < tr.timestampMin {
+			tr.timestampMin = typeutil.Timestamp(data)
+		}
+		if uint64(data) > tr.timestampMax {
+			tr.timestampMax = typeutil.Timestamp(data)
+		}
+	}
+	return tr
+}

internal/datanode/writebuffer/insert_buffer_test.go

@@ -0,0 +1,294 @@
+package writebuffer
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/samber/lo"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+	"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/storage"
+	"github.com/milvus-io/milvus/pkg/common"
+	"github.com/milvus-io/milvus/pkg/mq/msgstream"
+	"github.com/milvus-io/milvus/pkg/util/paramtable"
+	"github.com/milvus-io/milvus/pkg/util/tsoutil"
+)
+
+type InsertBufferSuite struct {
+	suite.Suite
+	collSchema *schemapb.CollectionSchema
+}
+
+func (s *InsertBufferSuite) SetupSuite() {
+	paramtable.Get().Init(paramtable.NewBaseTable())
+	s.collSchema = &schemapb.CollectionSchema{
+		Name: "test_collection",
+		Fields: []*schemapb.FieldSchema{
+			{
+				FieldID: common.RowIDField, Name: common.RowIDFieldName, DataType: schemapb.DataType_Int64,
+			},
+			{
+				FieldID: common.TimeStampField, Name: common.TimeStampFieldName, DataType: schemapb.DataType_Int64,
+			},
+			{
+				FieldID: 100, Name: "pk", DataType: schemapb.DataType_Int64, IsPrimaryKey: true,
+			},
+			{
+				FieldID: 101, Name: "vector", DataType: schemapb.DataType_FloatVector,
+				TypeParams: []*commonpb.KeyValuePair{
+					{Key: common.DimKey, Value: "128"},
+				},
+			},
+		},
+	}
+}
+
+func (s *InsertBufferSuite) composeInsertMsg(rowCount int, dim int) ([]int64, *msgstream.InsertMsg) {
+	tss := lo.RepeatBy(rowCount, func(idx int) int64 { return int64(tsoutil.ComposeTSByTime(time.Now(), int64(idx))) })
+	vectors := lo.RepeatBy(rowCount, func(_ int) []float32 {
+		return lo.RepeatBy(dim, func(_ int) float32 { return rand.Float32() })
+	})
+	flatten := lo.Flatten(vectors)
+	return tss, &msgstream.InsertMsg{
+		InsertRequest: msgpb.InsertRequest{
+			Version:    msgpb.InsertDataVersion_ColumnBased,
+			RowIDs:     tss,
+			Timestamps: lo.Map(tss, func(id int64, _ int) uint64 { return uint64(id) }),
+			FieldsData: []*schemapb.FieldData{
+				{
+					FieldId: common.RowIDField, FieldName: common.RowIDFieldName, Type: schemapb.DataType_Int64,
+					Field: &schemapb.FieldData_Scalars{
+						Scalars: &schemapb.ScalarField{
+							Data: &schemapb.ScalarField_LongData{
+								LongData: &schemapb.LongArray{
+									Data: tss,
+								},
+							},
+						},
+					},
+				},
+				{
+					FieldId: common.TimeStampField, FieldName: common.TimeStampFieldName, Type: schemapb.DataType_Int64,
+					Field: &schemapb.FieldData_Scalars{
+						Scalars: &schemapb.ScalarField{
+							Data: &schemapb.ScalarField_LongData{
+								LongData: &schemapb.LongArray{
+									Data: tss,
+								},
+							},
+						},
+					},
+				},
+				{
+					FieldId: common.StartOfUserFieldID, FieldName: "pk", Type: schemapb.DataType_Int64,
+					Field: &schemapb.FieldData_Scalars{
+						Scalars: &schemapb.ScalarField{
+							Data: &schemapb.ScalarField_LongData{
+								LongData: &schemapb.LongArray{
+									Data: tss,
+								},
+							},
+						},
+					},
+				},
+				{
+					FieldId: common.StartOfUserFieldID + 1, FieldName: "vector", Type: schemapb.DataType_FloatVector,
+					Field: &schemapb.FieldData_Vectors{
+						Vectors: &schemapb.VectorField{
+							Dim: int64(dim),
+							Data: &schemapb.VectorField_FloatVector{
+								FloatVector: &schemapb.FloatArray{
+									Data: flatten,
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+}
+
+func (s *InsertBufferSuite) TestBasic() {
+	s.Run("normal_insertbuffer", func() {
+		insertBuffer, err := NewInsertBuffer(s.collSchema)
+		s.Require().NoError(err)
+
+		s.True(insertBuffer.IsEmpty())
+		s.False(insertBuffer.IsFull())
+
+		insertBuffer.rows = insertBuffer.rowLimit + 1
+		s.True(insertBuffer.IsFull())
+		s.False(insertBuffer.IsEmpty())
+	})
+}
+
+func (s *InsertBufferSuite) TestBuffer() {
+	s.Run("normal_buffer", func() {
+		pks, insertMsg := s.composeInsertMsg(10, 128)
+
+		insertBuffer, err := NewInsertBuffer(s.collSchema)
+		s.Require().NoError(err)
+
+		fieldData, err := insertBuffer.Buffer([]*msgstream.InsertMsg{insertMsg}, &msgpb.MsgPosition{Timestamp: 100}, &msgpb.MsgPosition{Timestamp: 200})
+		s.NoError(err)
+
+		pkData := lo.Map(fieldData, func(fd storage.FieldData, _ int) []int64 {
+			return lo.RepeatBy(fd.RowNum(), func(idx int) int64 { return fd.GetRow(idx).(int64) })
+		})
+		s.ElementsMatch(pks, lo.Flatten(pkData))
+		s.EqualValues(100, insertBuffer.MinTimestamp())
+	})
+
+	s.Run("pk_not_found", func() {
+		_, insertMsg := s.composeInsertMsg(10, 128)
+
+		insertMsg.FieldsData = []*schemapb.FieldData{insertMsg.FieldsData[0], insertMsg.FieldsData[1], insertMsg.FieldsData[3]}
+
+		insertBuffer, err := NewInsertBuffer(s.collSchema)
+		s.Require().NoError(err)
+
+		_, err = insertBuffer.Buffer([]*msgstream.InsertMsg{insertMsg}, &msgpb.MsgPosition{Timestamp: 100}, &msgpb.MsgPosition{Timestamp: 200})
+		s.Error(err)
+	})
+
+	s.Run("schema_without_pk", func() {
+		badSchema := &schemapb.CollectionSchema{
+			Name: "test_collection",
+			Fields: []*schemapb.FieldSchema{
+				{
+					FieldID: common.RowIDField, Name: common.RowIDFieldName, DataType: schemapb.DataType_Int64,
+				},
+				{
+					FieldID: common.TimeStampField, Name: common.TimeStampFieldName, DataType: schemapb.DataType_Int64,
+				},
+				{
+					FieldID: 101, Name: "vector", DataType: schemapb.DataType_FloatVector,
+					TypeParams: []*commonpb.KeyValuePair{
+						{Key: common.DimKey, Value: "128"},
+					},
+				},
+			},
+		}
+
+		_, insertMsg := s.composeInsertMsg(10, 128)
+
+		insertBuffer, err := NewInsertBuffer(badSchema)
+		s.Require().NoError(err)
+
+		_, err = insertBuffer.Buffer([]*msgstream.InsertMsg{insertMsg}, &msgpb.MsgPosition{Timestamp: 100}, &msgpb.MsgPosition{Timestamp: 200})
+		s.Error(err)
+	})
+}
+
+func (s *InsertBufferSuite) TestRenew() {
+	insertBuffer, err := NewInsertBuffer(s.collSchema)
+	s.Require().NoError(err)
+
+	result := insertBuffer.Renew()
+	s.Nil(result)
+	s.True(insertBuffer.IsEmpty())
+
+	pks, insertMsg := s.composeInsertMsg(10, 128)
+	_, err = insertBuffer.Buffer([]*msgstream.InsertMsg{insertMsg}, &msgpb.MsgPosition{Timestamp: 100}, &msgpb.MsgPosition{Timestamp: 200})
+	s.Require().NoError(err)
+
+	result = insertBuffer.Renew()
+	s.NotNil(result)
+	s.True(insertBuffer.IsEmpty())
+
+	pkField, ok := result.Data[common.StartOfUserFieldID]
+	s.Require().True(ok)
+	pkData := lo.RepeatBy(pkField.RowNum(), func(idx int) int64 { return pkField.GetRow(idx).(int64) })
+	s.ElementsMatch(pks, pkData)
+}
+
+type InsertBufferConstructSuite struct {
+	suite.Suite
+	schema *schemapb.CollectionSchema
+}
+
+func (*InsertBufferConstructSuite) SetupSuite() {
+	paramtable.Get().Init(paramtable.NewBaseTable())
+}
+
+func (s *InsertBufferConstructSuite) TestCreateSuccess() {
+	schema := &schemapb.CollectionSchema{
+		Name: "test_collection",
+		Fields: []*schemapb.FieldSchema{
+			{
+				FieldID: 100, Name: "pk", DataType: schemapb.DataType_Int64, IsPrimaryKey: true,
+			},
+			{
+				FieldID: 101, Name: "vector", DataType: schemapb.DataType_FloatVector,
+				TypeParams: []*commonpb.KeyValuePair{
+					{Key: common.DimKey, Value: "128"},
+				},
+			},
+		},
+	}
+	insertBuffer, err := NewInsertBuffer(schema)
+	s.NoError(err)
+	s.NotNil(insertBuffer)
+}
+
+func (s *InsertBufferConstructSuite) TestCreateFailure() {
+	type testCase struct {
+		schema *schemapb.CollectionSchema
+		tag    string
+	}
+
+	cases := []testCase{
+		{
+			tag: "undefined_datatype",
+			schema: &schemapb.CollectionSchema{
+				Fields: []*schemapb.FieldSchema{
+					{FieldID: 101, Name: "vector", DataType: -1},
+				},
+			},
+		},
+		{
+			tag: "mssing_maxlength",
+			schema: &schemapb.CollectionSchema{
+				Fields: []*schemapb.FieldSchema{
+					{FieldID: 101, Name: "string", DataType: schemapb.DataType_VarChar},
+				},
+			},
+		},
+		{
+			tag: "empty_schema",
+			schema: &schemapb.CollectionSchema{
+				Fields: []*schemapb.FieldSchema{},
+			},
+		},
+		{
+			tag: "missing_type_param",
+			schema: &schemapb.CollectionSchema{
+				Name: "test_collection",
+				Fields: []*schemapb.FieldSchema{
+					{
+						FieldID: 100, Name: "pk", DataType: schemapb.DataType_Int64, IsPrimaryKey: true,
+					},
+					{
+						FieldID: 101, Name: "vector", DataType: schemapb.DataType_FloatVector,
+					},
+				},
+			},
+		},
+	}
+	for _, tc := range cases {
+		s.Run(tc.tag, func() {
+			_, err := NewInsertBuffer(tc.schema)
+			s.Error(err)
+		})
+	}
+}
+
+func TestInsertBuffer(t *testing.T) {
+	suite.Run(t, new(InsertBufferSuite))
+	suite.Run(t, new(InsertBufferConstructSuite))
+}

internal/datanode/writebuffer/l0_write_buffer.go

@@ -0,0 +1,83 @@
+package writebuffer
+
+import (
+	"context"
+
+	"go.uber.org/zap"
+
+	"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/allocator"
+	"github.com/milvus-io/milvus/internal/datanode/metacache"
+	"github.com/milvus-io/milvus/internal/datanode/syncmgr"
+	"github.com/milvus-io/milvus/internal/storage"
+	"github.com/milvus-io/milvus/pkg/log"
+	"github.com/milvus-io/milvus/pkg/mq/msgstream"
+	"github.com/milvus-io/milvus/pkg/util/merr"
+	"github.com/milvus-io/milvus/pkg/util/retry"
+)
+
+type l0WriteBuffer struct {
+	*writeBufferBase
+
+	l0Segments map[int64]int64 // partitionID => l0 segment ID
+
+	syncMgr     syncmgr.SyncManager
+	idAllocator allocator.Interface
+}
+
+func NewL0WriteBuffer(sch *schemapb.CollectionSchema, metacache metacache.MetaCache, syncMgr syncmgr.SyncManager, option *writeBufferOption) (WriteBuffer, error) {
+	if option.idAllocator == nil {
+		return nil, merr.WrapErrServiceInternal("id allocator is nil when creating l0 write buffer")
+	}
+	return &l0WriteBuffer{
+		l0Segments:      make(map[int64]int64),
+		writeBufferBase: newWriteBufferBase(sch, metacache, syncMgr, option),
+		syncMgr:         syncMgr,
+		idAllocator:     option.idAllocator,
+	}, nil
+}
+
+func (wb *l0WriteBuffer) BufferData(insertMsgs []*msgstream.InsertMsg, deleteMsgs []*msgstream.DeleteMsg, startPos, endPos *msgpb.MsgPosition) error {
+	wb.mut.Lock()
+	defer wb.mut.Unlock()
+
+	// process insert msgs
+	_, err := wb.bufferInsert(insertMsgs, startPos, endPos)
+	if err != nil {
+		log.Warn("failed to buffer insert data", zap.Error(err))
+		return err
+	}
+
+	for _, msg := range deleteMsgs {
+		l0SegmentID := wb.getL0SegmentID(msg.GetPartitionID())
+		pks := storage.ParseIDs2PrimaryKeys(msg.GetPrimaryKeys())
+		err := wb.bufferDelete(l0SegmentID, pks, msg.GetTimestamps(), startPos, endPos)
+		if err != nil {
+			log.Warn("failed to buffer delete data", zap.Error(err))
+			return err
+		}
+	}
+
+	// update buffer last checkpoint
+	wb.checkpoint = endPos
+
+	return wb.triggerAutoSync()
+}
+
+func (wb *l0WriteBuffer) getL0SegmentID(partitionID int64) int64 {
+	segmentID, ok := wb.l0Segments[partitionID]
+	if !ok {
+		err := retry.Do(context.Background(), func() error {
+			var err error
+			segmentID, err = wb.idAllocator.AllocOne()
+			return err
+		})
+		if err != nil {
+			log.Error("failed to allocate l0 segment ID", zap.Error(err))
+			panic(err)
+		}
+		wb.l0Segments[partitionID] = segmentID
+	}
+	return segmentID
+}

internal/datanode/writebuffer/l0_write_buffer_test.go

@@ -0,0 +1,158 @@
+package writebuffer
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/samber/lo"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+	"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/allocator"
+	"github.com/milvus-io/milvus/internal/datanode/metacache"
+	"github.com/milvus-io/milvus/internal/datanode/syncmgr"
+	"github.com/milvus-io/milvus/internal/storage"
+	"github.com/milvus-io/milvus/pkg/common"
+	"github.com/milvus-io/milvus/pkg/mq/msgstream"
+	"github.com/milvus-io/milvus/pkg/util/paramtable"
+	"github.com/milvus-io/milvus/pkg/util/tsoutil"
+)
+
+type L0WriteBufferSuite struct {
+	suite.Suite
+	collSchema *schemapb.CollectionSchema
+	syncMgr    *syncmgr.MockSyncManager
+	metacache  *metacache.MockMetaCache
+	allocator  *allocator.MockGIDAllocator
+}
+
+func (s *L0WriteBufferSuite) SetupSuite() {
+	paramtable.Get().Init(paramtable.NewBaseTable())
+	s.collSchema = &schemapb.CollectionSchema{
+		Name: "test_collection",
+		Fields: []*schemapb.FieldSchema{
+			{
+				FieldID: common.RowIDField, Name: common.RowIDFieldName, DataType: schemapb.DataType_Int64,
+			},
+			{
+				FieldID: common.TimeStampField, Name: common.TimeStampFieldName, DataType: schemapb.DataType_Int64,
+			},
+			{
+				FieldID: 100, Name: "pk", DataType: schemapb.DataType_Int64, IsPrimaryKey: true,
+			},
+			{
+				FieldID: 101, Name: "vector", DataType: schemapb.DataType_FloatVector,
+				TypeParams: []*commonpb.KeyValuePair{
+					{Key: common.DimKey, Value: "128"},
+				},
+			},
+		},
+	}
+}
+
+func (s *L0WriteBufferSuite) composeInsertMsg(segmentID int64, rowCount int, dim int) ([]int64, *msgstream.InsertMsg) {
+	tss := lo.RepeatBy(rowCount, func(idx int) int64 { return int64(tsoutil.ComposeTSByTime(time.Now(), int64(idx))) })
+	vectors := lo.RepeatBy(rowCount, func(_ int) []float32 {
+		return lo.RepeatBy(dim, func(_ int) float32 { return rand.Float32() })
+	})
+	flatten := lo.Flatten(vectors)
+	return tss, &msgstream.InsertMsg{
+		InsertRequest: msgpb.InsertRequest{
+			SegmentID:  segmentID,
+			Version:    msgpb.InsertDataVersion_ColumnBased,
+			RowIDs:     tss,
+			Timestamps: lo.Map(tss, func(id int64, _ int) uint64 { return uint64(id) }),
+			FieldsData: []*schemapb.FieldData{
+				{
+					FieldId: common.RowIDField, FieldName: common.RowIDFieldName, Type: schemapb.DataType_Int64,
+					Field: &schemapb.FieldData_Scalars{
+						Scalars: &schemapb.ScalarField{
+							Data: &schemapb.ScalarField_LongData{
+								LongData: &schemapb.LongArray{
+									Data: tss,
+								},
+							},
+						},
+					},
+				},
+				{
+					FieldId: common.TimeStampField, FieldName: common.TimeStampFieldName, Type: schemapb.DataType_Int64,
+					Field: &schemapb.FieldData_Scalars{
+						Scalars: &schemapb.ScalarField{
+							Data: &schemapb.ScalarField_LongData{
+								LongData: &schemapb.LongArray{
+									Data: tss,
+								},
+							},
+						},
+					},
+				},
+				{
+					FieldId: common.StartOfUserFieldID, FieldName: "pk", Type: schemapb.DataType_Int64,
+					Field: &schemapb.FieldData_Scalars{
+						Scalars: &schemapb.ScalarField{
+							Data: &schemapb.ScalarField_LongData{
+								LongData: &schemapb.LongArray{
+									Data: tss,
+								},
+							},
+						},
+					},
+				},
+				{
+					FieldId: common.StartOfUserFieldID + 1, FieldName: "vector", Type: schemapb.DataType_FloatVector,
+					Field: &schemapb.FieldData_Vectors{
+						Vectors: &schemapb.VectorField{
+							Dim: int64(dim),
+							Data: &schemapb.VectorField_FloatVector{
+								FloatVector: &schemapb.FloatArray{
+									Data: flatten,
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+}
+
+func (s *L0WriteBufferSuite) composeDeleteMsg(pks []storage.PrimaryKey) *msgstream.DeleteMsg {
+	delMsg := &msgstream.DeleteMsg{
+		DeleteRequest: msgpb.DeleteRequest{
+			PrimaryKeys: storage.ParsePrimaryKeys2IDs(pks),
+			Timestamps:  lo.RepeatBy(len(pks), func(idx int) uint64 { return tsoutil.ComposeTSByTime(time.Now(), int64(idx)) }),
+		},
+	}
+	return delMsg
+}
+
+func (s *L0WriteBufferSuite) SetupTest() {
+	s.syncMgr = syncmgr.NewMockSyncManager(s.T())
+	s.metacache = metacache.NewMockMetaCache(s.T())
+	s.allocator = allocator.NewMockGIDAllocator()
+	s.allocator.AllocOneF = func() (int64, error) { return int64(tsoutil.ComposeTSByTime(time.Now(), 0)), nil }
+}
+
+func (s *L0WriteBufferSuite) TestBufferData() {
+	wb, err := NewL0WriteBuffer(s.collSchema, s.metacache, s.syncMgr, &writeBufferOption{
+		idAllocator: s.allocator,
+	})
+	s.NoError(err)
+
+	// seg := metacache.NewSegmentInfo(&datapb.SegmentInfo{ID: 1000}, metacache.NewBloomFilterSet())
+	// s.metacache.EXPECT().GetSegmentsBy(mock.Anything).Return([]*metacache.SegmentInfo{seg})
+
+	pks, msg := s.composeInsertMsg(1000, 10, 128)
+	delMsg := s.composeDeleteMsg(lo.Map(pks, func(id int64, _ int) storage.PrimaryKey { return storage.NewInt64PrimaryKey(id) }))
+
+	err = wb.BufferData([]*msgstream.InsertMsg{msg}, []*msgstream.DeleteMsg{delMsg}, &msgpb.MsgPosition{Timestamp: 100}, &msgpb.MsgPosition{Timestamp: 200})
+	s.NoError(err)
+}
+
+func TestL0WriteBuffer(t *testing.T) {
+	suite.Run(t, new(L0WriteBufferSuite))
+}

internal/datanode/writebuffer/manager.go

@@ -0,0 +1,105 @@
+package writebuffer
+
+import (
+	"context"
+	"sync"
+
+	"go.uber.org/zap"
+
+	"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/datanode/metacache"
+	"github.com/milvus-io/milvus/internal/datanode/syncmgr"
+	"github.com/milvus-io/milvus/pkg/log"
+	"github.com/milvus-io/milvus/pkg/mq/msgstream"
+	"github.com/milvus-io/milvus/pkg/util/merr"
+)
+
+// Manager is the interface for WriteBuffer management.
+type Manager interface {
+	// Register adds a WriteBuffer with provided schema & options.
+	Register(channel string, schema *schemapb.CollectionSchema, metacache metacache.MetaCache, opts ...WriteBufferOption) error
+	// FlushSegments notifies writeBuffer corresponding to provided channel to flush segments.
+	FlushSegments(ctx context.Context, channel string, segmentIDs []int64) error
+	// RemoveChannel removes a write buffer from manager.
+	RemoveChannel(channel string)
+	// BufferData put data into channel write buffer.
+	BufferData(channel string, insertMsgs []*msgstream.InsertMsg, deleteMsgs []*msgstream.DeleteMsg, startPos, endPos *msgpb.MsgPosition) error
+}
+
+// NewManager returns initialized manager as `Manager`
+func NewManager(syncMgr syncmgr.SyncManager) Manager {
+	return &manager{
+		syncMgr: syncMgr,
+		buffers: make(map[string]WriteBuffer),
+	}
+}
+
+type manager struct {
+	syncMgr syncmgr.SyncManager
+	buffers map[string]WriteBuffer
+	mut     sync.RWMutex
+}
+
+// Register a new WriteBuffer for channel.
+func (m *manager) Register(channel string, schema *schemapb.CollectionSchema, metacache metacache.MetaCache, opts ...WriteBufferOption) error {
+	m.mut.Lock()
+	defer m.mut.Unlock()
+
+	_, ok := m.buffers[channel]
+	if ok {
+		return merr.WrapErrChannelReduplicate(channel)
+	}
+	buf, err := NewWriteBuffer(schema, metacache, m.syncMgr, opts...)
+	if err != nil {
+		return err
+	}
+	m.buffers[channel] = buf
+	return nil
+}
+
+// FlushSegments call sync segment and change segments state to Flushed.
+func (m *manager) FlushSegments(ctx context.Context, channel string, segmentIDs []int64) error {
+	m.mut.RLock()
+	buf, ok := m.buffers[channel]
+	m.mut.RUnlock()
+
+	if !ok {
+		log.Ctx(ctx).Warn("write buffer not found when flush segments",
+			zap.String("channel", channel),
+			zap.Int64s("segmentIDs", segmentIDs))
+		return merr.WrapErrChannelNotFound(channel)
+	}
+
+	return buf.FlushSegments(ctx, segmentIDs)
+}
+
+// BufferData put data into channel write buffer.
+func (m *manager) BufferData(channel string, insertMsgs []*msgstream.InsertMsg, deleteMsgs []*msgstream.DeleteMsg, startPos, endPos *msgpb.MsgPosition) error {
+	m.mut.RLock()
+	buf, ok := m.buffers[channel]
+	m.mut.RUnlock()
+
+	if !ok {
+		log.Ctx(context.Background()).Warn("write buffer not found when buffer data",
+			zap.String("channel", channel))
+		return merr.WrapErrChannelNotFound(channel)
+	}
+
+	return buf.BufferData(insertMsgs, deleteMsgs, startPos, endPos)
+}
+
+// RemoveChannel remove channel WriteBuffer from manager.
+func (m *manager) RemoveChannel(channel string) {
+	m.mut.Lock()
+	buf, ok := m.buffers[channel]
+	delete(m.buffers, channel)
+	m.mut.Unlock()
+
+	if !ok {
+		log.Warn("failed to remove channel, channel not maintained in manager", zap.String("channel", channel))
+		return
+	}
+
+	buf.Close()
+}

internal/datanode/writebuffer/manager_test.go

@@ -0,0 +1,138 @@
+package writebuffer
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+	"github.com/milvus-io/milvus-proto/go-api/v2/schemapb"
+	"github.com/milvus-io/milvus/internal/datanode/metacache"
+	"github.com/milvus-io/milvus/internal/datanode/syncmgr"
+	"github.com/milvus-io/milvus/pkg/common"
+	"github.com/milvus-io/milvus/pkg/util/merr"
+	"github.com/milvus-io/milvus/pkg/util/paramtable"
+)
+
+type ManagerSuite struct {
+	suite.Suite
+	channelName string
+	collSchema  *schemapb.CollectionSchema
+	syncMgr     *syncmgr.MockSyncManager
+	metacache   *metacache.MockMetaCache
+
+	manager *manager
+}
+
+func (s *ManagerSuite) SetupSuite() {
+	paramtable.Get().Init(paramtable.NewBaseTable())
+	s.collSchema = &schemapb.CollectionSchema{
+		Name: "test_collection",
+		Fields: []*schemapb.FieldSchema{
+			{
+				FieldID: 100, Name: "pk", DataType: schemapb.DataType_Int64, IsPrimaryKey: true,
+			},
+			{
+				FieldID: 101, Name: "vector", DataType: schemapb.DataType_FloatVector,
+				TypeParams: []*commonpb.KeyValuePair{
+					{Key: common.DimKey, Value: "128"},
+				},
+			},
+		},
+	}
+
+	s.channelName = "by-dev-rootcoord-dml_0_100_v0"
+}
+
+func (s *ManagerSuite) SetupTest() {
+	s.syncMgr = syncmgr.NewMockSyncManager(s.T())
+	s.metacache = metacache.NewMockMetaCache(s.T())
+
+	mgr := NewManager(s.syncMgr)
+	var ok bool
+	s.manager, ok = mgr.(*manager)
+	s.Require().True(ok)
+}
+
+func (s *ManagerSuite) TestRegister() {
+	manager := s.manager
+
+	err := manager.Register(s.channelName, s.collSchema, s.metacache)
+	s.NoError(err)
+
+	err = manager.Register(s.channelName, s.collSchema, s.metacache)
+	s.Error(err)
+	s.ErrorIs(err, merr.ErrChannelReduplicate)
+}
+
+func (s *ManagerSuite) TestFlushSegments() {
+	manager := s.manager
+	s.Run("channel_not_found", func() {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		err := manager.FlushSegments(ctx, s.channelName, []int64{1, 2, 3})
+		s.Error(err, "FlushSegments shall return error when channel not found")
+	})
+
+	s.Run("normal_flush", func() {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+
+		wb := NewMockWriteBuffer(s.T())
+
+		s.manager.mut.Lock()
+		s.manager.buffers[s.channelName] = wb
+		s.manager.mut.Unlock()
+
+		wb.EXPECT().FlushSegments(mock.Anything, mock.Anything).Return(nil)
+
+		err := manager.FlushSegments(ctx, s.channelName, []int64{1})
+		s.NoError(err)
+	})
+}
+
+func (s *ManagerSuite) TestBufferData() {
+	manager := s.manager
+	s.Run("channel_not_found", func() {
+		err := manager.BufferData(s.channelName, nil, nil, nil, nil)
+		s.Error(err, "FlushSegments shall return error when channel not found")
+	})
+
+	s.Run("normal_buffer_data", func() {
+		wb := NewMockWriteBuffer(s.T())
+
+		s.manager.mut.Lock()
+		s.manager.buffers[s.channelName] = wb
+		s.manager.mut.Unlock()
+
+		wb.EXPECT().BufferData(mock.Anything, mock.Anything, mock.Anything, mock.Anything).Return(nil)
+
+		err := manager.BufferData(s.channelName, nil, nil, nil, nil)
+		s.NoError(err)
+	})
+}
+
+func (s *ManagerSuite) TestRemoveChannel() {
+	manager := NewManager(s.syncMgr)
+
+	s.Run("remove_not_exist", func() {
+		s.NotPanics(func() {
+			manager.RemoveChannel(s.channelName)
+		})
+	})
+
+	s.Run("remove_channel", func() {
+		err := manager.Register(s.channelName, s.collSchema, s.metacache)
+		s.Require().NoError(err)
+
+		s.NotPanics(func() {
+			manager.RemoveChannel(s.channelName)
+		})
+	})
+}
+
+func TestManager(t *testing.T) {
+	suite.Run(t, new(ManagerSuite))
+}

internal/datanode/writebuffer/mock_write_buffer.go

@@ -0,0 +1,201 @@
+// Code generated by mockery v2.32.4. DO NOT EDIT.
+
+package writebuffer
+
+import (
+	context "context"
+
+	msgpb "github.com/milvus-io/milvus-proto/go-api/v2/msgpb"
+	mock "github.com/stretchr/testify/mock"
+
+	msgstream "github.com/milvus-io/milvus/pkg/mq/msgstream"
+)
+
+// MockWriteBuffer is an autogenerated mock type for the WriteBuffer type
+type MockWriteBuffer struct {
+	mock.Mock
+}
+
+type MockWriteBuffer_Expecter struct {
+	mock *mock.Mock
+}
+
+func (_m *MockWriteBuffer) EXPECT() *MockWriteBuffer_Expecter {
+	return &MockWriteBuffer_Expecter{mock: &_m.Mock}
+}
+
+// BufferData provides a mock function with given fields: insertMsgs, deleteMsgs, startPos, endPos
+func (_m *MockWriteBuffer) BufferData(insertMsgs []*msgstream.InsertMsg, deleteMsgs []*msgstream.DeleteMsg, startPos *msgpb.MsgPosition, endPos *msgpb.MsgPosition) error {
+	ret := _m.Called(insertMsgs, deleteMsgs, startPos, endPos)
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func([]*msgstream.InsertMsg, []*msgstream.DeleteMsg, *msgpb.MsgPosition, *msgpb.MsgPosition) error); ok {
+		r0 = rf(insertMsgs, deleteMsgs, startPos, endPos)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
+// MockWriteBuffer_BufferData_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'BufferData'
+type MockWriteBuffer_BufferData_Call struct {
+	*mock.Call
+}
+
+// BufferData is a helper method to define mock.On call
+//   - insertMsgs []*msgstream.InsertMsg
+//   - deleteMsgs []*msgstream.DeleteMsg
+//   - startPos *msgpb.MsgPosition
+//   - endPos *msgpb.MsgPosition
+func (_e *MockWriteBuffer_Expecter) BufferData(insertMsgs interface{}, deleteMsgs interface{}, startPos interface{}, endPos interface{}) *MockWriteBuffer_BufferData_Call {
+	return &MockWriteBuffer_BufferData_Call{Call: _e.mock.On("BufferData", insertMsgs, deleteMsgs, startPos, endPos)}
+}
+
+func (_c *MockWriteBuffer_BufferData_Call) Run(run func(insertMsgs []*msgstream.InsertMsg, deleteMsgs []*msgstream.DeleteMsg, startPos *msgpb.MsgPosition, endPos *msgpb.MsgPosition)) *MockWriteBuffer_BufferData_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run(args[0].([]*msgstream.InsertMsg), args[1].([]*msgstream.DeleteMsg), args[2].(*msgpb.MsgPosition), args[3].(*msgpb.MsgPosition))
+	})
+	return _c
+}
+
+func (_c *MockWriteBuffer_BufferData_Call) Return(_a0 error) *MockWriteBuffer_BufferData_Call {
+	_c.Call.Return(_a0)
+	return _c
+}
+
+func (_c *MockWriteBuffer_BufferData_Call) RunAndReturn(run func([]*msgstream.InsertMsg, []*msgstream.DeleteMsg, *msgpb.MsgPosition, *msgpb.MsgPosition) error) *MockWriteBuffer_BufferData_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
+// Close provides a mock function with given fields:
+func (_m *MockWriteBuffer) Close() {
+	_m.Called()
+}
+
+// MockWriteBuffer_Close_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'Close'
+type MockWriteBuffer_Close_Call struct {
+	*mock.Call
+}
+
+// Close is a helper method to define mock.On call
+func (_e *MockWriteBuffer_Expecter) Close() *MockWriteBuffer_Close_Call {
+	return &MockWriteBuffer_Close_Call{Call: _e.mock.On("Close")}
+}
+
+func (_c *MockWriteBuffer_Close_Call) Run(run func()) *MockWriteBuffer_Close_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run()
+	})
+	return _c
+}
+
+func (_c *MockWriteBuffer_Close_Call) Return() *MockWriteBuffer_Close_Call {
+	_c.Call.Return()
+	return _c
+}
+
+func (_c *MockWriteBuffer_Close_Call) RunAndReturn(run func()) *MockWriteBuffer_Close_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
+// FlushSegments provides a mock function with given fields: ctx, segmentIDs
+func (_m *MockWriteBuffer) FlushSegments(ctx context.Context, segmentIDs []int64) error {
+	ret := _m.Called(ctx, segmentIDs)
+
+	var r0 error
+	if rf, ok := ret.Get(0).(func(context.Context, []int64) error); ok {
+		r0 = rf(ctx, segmentIDs)
+	} else {
+		r0 = ret.Error(0)
+	}
+
+	return r0
+}
+
+// MockWriteBuffer_FlushSegments_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'FlushSegments'
+type MockWriteBuffer_FlushSegments_Call struct {
+	*mock.Call
+}
+
+// FlushSegments is a helper method to define mock.On call
+//   - ctx context.Context
+//   - segmentIDs []int64
+func (_e *MockWriteBuffer_Expecter) FlushSegments(ctx interface{}, segmentIDs interface{}) *MockWriteBuffer_FlushSegments_Call {
+	return &MockWriteBuffer_FlushSegments_Call{Call: _e.mock.On("FlushSegments", ctx, segmentIDs)}
+}
+
+func (_c *MockWriteBuffer_FlushSegments_Call) Run(run func(ctx context.Context, segmentIDs []int64)) *MockWriteBuffer_FlushSegments_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run(args[0].(context.Context), args[1].([]int64))
+	})
+	return _c
+}
+
+func (_c *MockWriteBuffer_FlushSegments_Call) Return(_a0 error) *MockWriteBuffer_FlushSegments_Call {
+	_c.Call.Return(_a0)
+	return _c
+}
+
+func (_c *MockWriteBuffer_FlushSegments_Call) RunAndReturn(run func(context.Context, []int64) error) *MockWriteBuffer_FlushSegments_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
+// HasSegment provides a mock function with given fields: segmentID
+func (_m *MockWriteBuffer) HasSegment(segmentID int64) bool {
+	ret := _m.Called(segmentID)
+
+	var r0 bool
+	if rf, ok := ret.Get(0).(func(int64) bool); ok {
+		r0 = rf(segmentID)
+	} else {
+		r0 = ret.Get(0).(bool)
+	}
+
+	return r0
+}
+
+// MockWriteBuffer_HasSegment_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'HasSegment'
+type MockWriteBuffer_HasSegment_Call struct {
+	*mock.Call
+}
+
+// HasSegment is a helper method to define mock.On call
+//   - segmentID int64
+func (_e *MockWriteBuffer_Expecter) HasSegment(segmentID interface{}) *MockWriteBuffer_HasSegment_Call {
+	return &MockWriteBuffer_HasSegment_Call{Call: _e.mock.On("HasSegment", segmentID)}
+}
+
+func (_c *MockWriteBuffer_HasSegment_Call) Run(run func(segmentID int64)) *MockWriteBuffer_HasSegment_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run(args[0].(int64))
+	})
+	return _c
+}
+
+func (_c *MockWriteBuffer_HasSegment_Call) Return(_a0 bool) *MockWriteBuffer_HasSegment_Call {
+	_c.Call.Return(_a0)
+	return _c
+}
+
+func (_c *MockWriteBuffer_HasSegment_Call) RunAndReturn(run func(int64) bool) *MockWriteBuffer_HasSegment_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
+// NewMockWriteBuffer creates a new instance of MockWriteBuffer. It also registers a testing interface on the mock and a cleanup function to assert the mocks expectations.
+// The first argument is typically a *testing.T value.
+func NewMockWriteBuffer(t interface {
+	mock.TestingT
+	Cleanup(func())
+}) *MockWriteBuffer {
+	mock := &MockWriteBuffer{}
+	mock.Mock.Test(t)
+
+	t.Cleanup(func() { mock.AssertExpectations(t) })
+
+	return mock
+}

internal/datanode/writebuffer/options.go

@@ -0,0 +1,70 @@
+package writebuffer
+
+import (
+	"time"
+
+	"github.com/milvus-io/milvus/internal/allocator"
+	"github.com/milvus-io/milvus/internal/datanode/broker"
+	"github.com/milvus-io/milvus/internal/datanode/metacache"
+	"github.com/milvus-io/milvus/pkg/util/paramtable"
+)
+
+const (
+	// DeletePolicyBFPKOracle is the const config value for using bf pk oracle as delete policy
+	DeletePolicyBFPkOracle = `bloom_filter_pkoracle`
+
+	// DeletePolicyL0Delta is the const config value for using L0 delta as deleta policy.
+	DeletePolicyL0Delta = `l0_delta`
+)
+
+type WriteBufferOption func(opt *writeBufferOption)
+
+type writeBufferOption struct {
+	deletePolicy string
+	idAllocator  allocator.Interface
+	syncPolicies []SyncPolicy
+
+	pkStatsFactory metacache.PkStatsFactory
+	broker         broker.Broker
+}
+
+func defaultWBOption() *writeBufferOption {
+	return &writeBufferOption{
+		// TODO use l0 delta as default after implementation.
+		deletePolicy: paramtable.Get().DataNodeCfg.DeltaPolicy.GetValue(),
+		syncPolicies: []SyncPolicy{
+			SyncFullBuffer,
+			GetSyncStaleBufferPolicy(paramtable.Get().DataNodeCfg.SyncPeriod.GetAsDuration(time.Second)),
+		},
+	}
+}
+
+func WithDeletePolicy(policy string) WriteBufferOption {
+	return func(opt *writeBufferOption) {
+		opt.deletePolicy = policy
+	}
+}
+
+func WithIDAllocator(allocator allocator.Interface) WriteBufferOption {
+	return func(opt *writeBufferOption) {
+		opt.idAllocator = allocator
+	}
+}
+
+func WithPKStatsFactory(factory metacache.PkStatsFactory) WriteBufferOption {
+	return func(opt *writeBufferOption) {
+		opt.pkStatsFactory = factory
+	}
+}
+
+func WithBroker(broker broker.Broker) WriteBufferOption {
+	return func(opt *writeBufferOption) {
+		opt.broker = broker
+	}
+}
+
+func WithSyncPolicy(policy SyncPolicy) WriteBufferOption {
+	return func(opt *writeBufferOption) {
+		opt.syncPolicies = append(opt.syncPolicies, policy)
+	}
+}

internal/datanode/writebuffer/segment_buffer.go

@@ -0,0 +1,56 @@
+package writebuffer
+
+import (
+	"github.com/milvus-io/milvus-proto/go-api/v2/schemapb"
+	"github.com/milvus-io/milvus/internal/storage"
+	"github.com/milvus-io/milvus/pkg/util/typeutil"
+)
+
+type segmentBuffer struct {
+	segmentID int64
+
+	insertBuffer *InsertBuffer
+	deltaBuffer  *DeltaBuffer
+
+	flushing bool
+}
+
+func newSegmentBuffer(segmentID int64, collSchema *schemapb.CollectionSchema) (*segmentBuffer, error) {
+	insertBuffer, err := NewInsertBuffer(collSchema)
+	if err != nil {
+		return nil, err
+	}
+	return &segmentBuffer{
+		segmentID:    segmentID,
+		insertBuffer: insertBuffer,
+		deltaBuffer:  NewDeltaBuffer(),
+	}, nil
+}
+
+func (buf *segmentBuffer) IsFull() bool {
+	return buf.insertBuffer.IsFull() || buf.deltaBuffer.IsFull()
+}
+
+func (buf *segmentBuffer) Renew() (insert *storage.InsertData, delete *storage.DeleteData) {
+	return buf.insertBuffer.Renew(), buf.deltaBuffer.Renew()
+}
+
+func (buf *segmentBuffer) SetFlush() {
+	buf.flushing = true
+}
+
+func (buf *segmentBuffer) MinTimestamp() typeutil.Timestamp {
+	insertTs := buf.insertBuffer.MinTimestamp()
+	deltaTs := buf.deltaBuffer.MinTimestamp()
+
+	if insertTs < deltaTs {
+		return insertTs
+	}
+	return deltaTs
+}
+
+// TimeRange is a range of timestamp contains the min-timestamp and max-timestamp
+type TimeRange struct {
+	timestampMin typeutil.Timestamp
+	timestampMax typeutil.Timestamp
+}

internal/datanode/writebuffer/sync_policy.go

@@ -0,0 +1,38 @@
+package writebuffer
+
+import (
+	"time"
+
+	"github.com/samber/lo"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+	"github.com/milvus-io/milvus/internal/datanode/metacache"
+	"github.com/milvus-io/milvus/pkg/util/tsoutil"
+	"github.com/milvus-io/milvus/pkg/util/typeutil"
+)
+
+type SyncPolicy func(buffers []*segmentBuffer, ts typeutil.Timestamp) []int64
+
+func SyncFullBuffer(buffers []*segmentBuffer, _ typeutil.Timestamp) []int64 {
+	return lo.FilterMap(buffers, func(buf *segmentBuffer, _ int) (int64, bool) {
+		return buf.segmentID, buf.IsFull()
+	})
+}
+
+func GetSyncStaleBufferPolicy(staleDuration time.Duration) SyncPolicy {
+	return func(buffers []*segmentBuffer, ts typeutil.Timestamp) []int64 {
+		current := tsoutil.PhysicalTime(ts)
+		return lo.FilterMap(buffers, func(buf *segmentBuffer, _ int) (int64, bool) {
+			minTs := buf.MinTimestamp()
+			start := tsoutil.PhysicalTime(minTs)
+
+			return buf.segmentID, current.Sub(start) > staleDuration
+		})
+	}
+}
+
+func GetFlushingSegmentsPolicy(meta metacache.MetaCache) SyncPolicy {
+	return func(_ []*segmentBuffer, _ typeutil.Timestamp) []int64 {
+		return meta.GetSegmentIDsBy(metacache.WithSegmentState(commonpb.SegmentState_Flushing))
+	}
+}

internal/datanode/writebuffer/sync_policy_test.go

@@ -0,0 +1,80 @@
+package writebuffer
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+	"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/datanode/metacache"
+	"github.com/milvus-io/milvus/pkg/common"
+	"github.com/milvus-io/milvus/pkg/util/paramtable"
+	"github.com/milvus-io/milvus/pkg/util/tsoutil"
+)
+
+type SyncPolicySuite struct {
+	suite.Suite
+	collSchema *schemapb.CollectionSchema
+}
+
+func (s *SyncPolicySuite) SetupSuite() {
+	paramtable.Get().Init(paramtable.NewBaseTable())
+
+	s.collSchema = &schemapb.CollectionSchema{
+		Name: "wb_base_collection",
+		Fields: []*schemapb.FieldSchema{
+			{FieldID: 100, DataType: schemapb.DataType_Int64, IsPrimaryKey: true, Name: "pk"},
+			{FieldID: 101, DataType: schemapb.DataType_FloatVector, TypeParams: []*commonpb.KeyValuePair{
+				{Key: common.DimKey, Value: "128"},
+			}},
+		},
+	}
+}
+
+func (s *SyncPolicySuite) TestSyncFullBuffer() {
+	buffer, err := newSegmentBuffer(100, s.collSchema)
+	s.Require().NoError(err)
+
+	ids := SyncFullBuffer([]*segmentBuffer{buffer}, 0)
+	s.Equal(0, len(ids), "empty buffer shall not be synced")
+
+	buffer.insertBuffer.rows = buffer.insertBuffer.rowLimit + 1
+
+	ids = SyncFullBuffer([]*segmentBuffer{buffer}, 0)
+	s.ElementsMatch([]int64{100}, ids)
+}
+
+func (s *SyncPolicySuite) TestSyncStalePolicy() {
+	policy := GetSyncStaleBufferPolicy(time.Minute)
+
+	buffer, err := newSegmentBuffer(100, s.collSchema)
+	s.Require().NoError(err)
+
+	ids := policy([]*segmentBuffer{buffer}, tsoutil.ComposeTSByTime(time.Now(), 0))
+	s.Equal(0, len(ids), "empty buffer shall not be synced")
+
+	buffer.insertBuffer.startPos = &msgpb.MsgPosition{
+		Timestamp: tsoutil.ComposeTSByTime(time.Now().Add(-time.Minute*2), 0),
+	}
+
+	ids = policy([]*segmentBuffer{buffer}, tsoutil.ComposeTSByTime(time.Now(), 0))
+	s.ElementsMatch([]int64{100}, ids)
+}
+
+func (s *SyncPolicySuite) TestFlushingSegmentsPolicy() {
+	metacache := metacache.NewMockMetaCache(s.T())
+	policy := GetFlushingSegmentsPolicy(metacache)
+	ids := []int64{1, 2, 3}
+	metacache.EXPECT().GetSegmentIDsBy(mock.Anything).Return(ids)
+
+	result := policy([]*segmentBuffer{}, tsoutil.ComposeTSByTime(time.Now(), 0))
+	s.ElementsMatch(ids, result)
+}
+
+func TestSyncPolicy(t *testing.T) {
+	suite.Run(t, new(SyncPolicySuite))
+}

internal/datanode/writebuffer/write_buffer.go

@@ -0,0 +1,226 @@
+package writebuffer
+
+import (
+	"context"
+	"sync"
+
+	"github.com/samber/lo"
+	"go.uber.org/zap"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+	"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/datanode/broker"
+	"github.com/milvus-io/milvus/internal/datanode/metacache"
+	"github.com/milvus-io/milvus/internal/datanode/syncmgr"
+	"github.com/milvus-io/milvus/internal/storage"
+	"github.com/milvus-io/milvus/pkg/log"
+	"github.com/milvus-io/milvus/pkg/mq/msgstream"
+	"github.com/milvus-io/milvus/pkg/util/merr"
+	"github.com/milvus-io/milvus/pkg/util/typeutil"
+)
+
+// WriteBuffer is the interface for channel write buffer.
+// It provides abstraction for channel write buffer and pk bloom filter & L0 delta logic.
+type WriteBuffer interface {
+	// HasSegment checks whether certain segment exists in this buffer.
+	HasSegment(segmentID int64) bool
+	// BufferData is the method to buffer dml data msgs.
+	BufferData(insertMsgs []*msgstream.InsertMsg, deleteMsgs []*msgstream.DeleteMsg, startPos, endPos *msgpb.MsgPosition) error
+	// FlushSegments is the method to perform `Sync` operation with provided options.
+	FlushSegments(ctx context.Context, segmentIDs []int64) error
+	// Close is the method to close and sink current buffer data.
+	Close()
+}
+
+func NewWriteBuffer(schema *schemapb.CollectionSchema, metacache metacache.MetaCache, syncMgr syncmgr.SyncManager, opts ...WriteBufferOption) (WriteBuffer, error) {
+	option := defaultWBOption()
+	option.syncPolicies = append(option.syncPolicies, GetFlushingSegmentsPolicy(metacache))
+	for _, opt := range opts {
+		opt(option)
+	}
+
+	switch option.deletePolicy {
+	case DeletePolicyBFPkOracle:
+		return NewBFWriteBuffer(schema, metacache, syncMgr, option)
+	case DeletePolicyL0Delta:
+		return NewL0WriteBuffer(schema, metacache, syncMgr, option)
+	default:
+		return nil, merr.WrapErrParameterInvalid("valid delete policy config", option.deletePolicy)
+	}
+}
+
+// writeBufferBase is the common component for buffering data
+type writeBufferBase struct {
+	mut sync.RWMutex
+
+	collectionID int64
+
+	collSchema *schemapb.CollectionSchema
+	metaCache  metacache.MetaCache
+	syncMgr    syncmgr.SyncManager
+	broker     broker.Broker
+	buffers    map[int64]*segmentBuffer // segmentID => segmentBuffer
+
+	syncPolicies []SyncPolicy
+	checkpoint   *msgpb.MsgPosition
+}
+
+func newWriteBufferBase(sch *schemapb.CollectionSchema, metacache metacache.MetaCache, syncMgr syncmgr.SyncManager, option *writeBufferOption) *writeBufferBase {
+	return &writeBufferBase{
+		collSchema:   sch,
+		syncMgr:      syncMgr,
+		broker:       option.broker,
+		buffers:      make(map[int64]*segmentBuffer),
+		metaCache:    metacache,
+		syncPolicies: option.syncPolicies,
+	}
+}
+
+func (wb *writeBufferBase) HasSegment(segmentID int64) bool {
+	wb.mut.RLock()
+	defer wb.mut.RUnlock()
+
+	_, ok := wb.buffers[segmentID]
+	return ok
+}
+
+func (wb *writeBufferBase) FlushSegments(ctx context.Context, segmentIDs []int64) error {
+	wb.mut.RLock()
+	defer wb.mut.RUnlock()
+
+	return wb.flushSegments(ctx, segmentIDs)
+}
+
+func (wb *writeBufferBase) triggerAutoSync() error {
+	segmentsToSync := wb.getSegmentsToSync(wb.checkpoint.GetTimestamp())
+	if len(segmentsToSync) > 0 {
+		log.Info("write buffer get segments to sync", zap.Int64s("segmentIDs", segmentsToSync))
+		err := wb.syncSegments(context.Background(), segmentsToSync)
+		if err != nil {
+			log.Warn("segment segments failed", zap.Int64s("segmentIDs", segmentsToSync), zap.Error(err))
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (wb *writeBufferBase) flushSegments(ctx context.Context, segmentIDs []int64) error {
+	// mark segment flushing if segment was growing
+	wb.metaCache.UpdateSegments(metacache.UpdateState(commonpb.SegmentState_Flushing),
+		metacache.WithSegmentIDs(segmentIDs...),
+		metacache.WithSegmentState(commonpb.SegmentState_Growing))
+	return nil
+}
+
+func (wb *writeBufferBase) syncSegments(ctx context.Context, segmentIDs []int64) error {
+	log := log.Ctx(ctx)
+	for _, segmentID := range segmentIDs {
+		infos := wb.metaCache.GetSegmentsBy(metacache.WithSegmentIDs(segmentID))
+		if len(infos) == 0 {
+			log.Warn("segment info not found in meta cache", zap.Int64("segmentID", segmentID))
+			continue
+		}
+		segmentInfo := infos[0]
+
+		buffer, exist := wb.getBuffer(segmentID)
+
+		var insert *storage.InsertData
+		var delta *storage.DeleteData
+		if exist {
+			insert, delta = buffer.Renew()
+		}
+
+		wb.metaCache.UpdateSegments(metacache.RollStats(), metacache.WithSegmentIDs(segmentID))
+
+		syncTask := syncmgr.NewSyncTask().
+			WithInsertData(insert).
+			WithDeleteData(delta).
+			WithCollectionID(wb.collectionID).
+			WithPartitionID(segmentInfo.PartitionID()).
+			WithSegmentID(segmentID).
+			WithCheckpoint(wb.checkpoint).
+			WithSchema(wb.collSchema).
+			WithMetaWriter(syncmgr.BrokerMetaWriter(wb.broker)).
+			WithFailureCallback(func(err error) {
+				// TODO could change to unsub channel in the future
+				panic(err)
+			})
+
+		// update flush& drop state
+		switch segmentInfo.State() {
+		case commonpb.SegmentState_Flushing:
+			syncTask.WithFlush()
+		case commonpb.SegmentState_Dropped:
+			syncTask.WithDrop()
+		}
+
+		err := wb.syncMgr.SyncData(ctx, syncTask)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// getSegmentsToSync applies all policies to get segments list to sync.
+// **NOTE** shall be invoked within mutex protection
+func (wb *writeBufferBase) getSegmentsToSync(ts typeutil.Timestamp) []int64 {
+	buffers := lo.Values(wb.buffers)
+	segments := typeutil.NewSet[int64]()
+	for _, policy := range wb.syncPolicies {
+		segments.Insert(policy(buffers, ts)...)
+	}
+
+	return segments.Collect()
+}
+
+func (wb *writeBufferBase) getOrCreateBuffer(segmentID int64) *segmentBuffer {
+	buffer, ok := wb.buffers[segmentID]
+	if !ok {
+		var err error
+		buffer, err = newSegmentBuffer(segmentID, wb.collSchema)
+		if err != nil {
+			// TODO avoid panic here
+			panic(err)
+		}
+		wb.buffers[segmentID] = buffer
+	}
+
+	return buffer
+}
+
+func (wb *writeBufferBase) getBuffer(segmentID int64) (*segmentBuffer, bool) {
+	buffer, ok := wb.buffers[segmentID]
+	return buffer, ok
+}
+
+// bufferInsert transform InsertMsg into bufferred InsertData and returns primary key field data for future usage.
+func (wb *writeBufferBase) bufferInsert(insertMsgs []*msgstream.InsertMsg, startPos, endPos *msgpb.MsgPosition) (map[int64][]storage.FieldData, error) {
+	insertGroups := lo.GroupBy(insertMsgs, func(msg *msgstream.InsertMsg) int64 { return msg.GetSegmentID() })
+	segmentPKData := make(map[int64][]storage.FieldData)
+
+	for segmentID, msgs := range insertGroups {
+		segBuf := wb.getOrCreateBuffer(segmentID)
+
+		pkData, err := segBuf.insertBuffer.Buffer(msgs, startPos, endPos)
+		if err != nil {
+			log.Warn("failed to buffer insert data", zap.Int64("segmentID", segmentID), zap.Error(err))
+			return nil, err
+		}
+		segmentPKData[segmentID] = pkData
+	}
+
+	return segmentPKData, nil
+}
+
+// bufferDelete buffers DeleteMsg into DeleteData.
+func (wb *writeBufferBase) bufferDelete(segmentID int64, pks []storage.PrimaryKey, tss []typeutil.Timestamp, startPos, endPos *msgpb.MsgPosition) error {
+	segBuf := wb.getOrCreateBuffer(segmentID)
+	segBuf.deltaBuffer.Buffer(pks, tss, startPos, endPos)
+	return nil
+}
+
+func (wb *writeBufferBase) Close() {
+}

internal/datanode/writebuffer/write_buffer_test.go

@@ -0,0 +1,91 @@
+package writebuffer
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/milvus-io/milvus-proto/go-api/v2/commonpb"
+	"github.com/milvus-io/milvus-proto/go-api/v2/schemapb"
+	"github.com/milvus-io/milvus/internal/allocator"
+	"github.com/milvus-io/milvus/internal/datanode/metacache"
+	"github.com/milvus-io/milvus/internal/datanode/syncmgr"
+	"github.com/milvus-io/milvus/internal/proto/datapb"
+	"github.com/milvus-io/milvus/pkg/common"
+	"github.com/milvus-io/milvus/pkg/util/paramtable"
+)
+
+type WriteBufferSuite struct {
+	suite.Suite
+	collSchema *schemapb.CollectionSchema
+	wb         *writeBufferBase
+	syncMgr    *syncmgr.MockSyncManager
+	metacache  *metacache.MockMetaCache
+}
+
+func (s *WriteBufferSuite) SetupSuite() {
+	paramtable.Get().Init(paramtable.NewBaseTable())
+	s.collSchema = &schemapb.CollectionSchema{
+		Name: "wb_base_collection",
+		Fields: []*schemapb.FieldSchema{
+			{FieldID: 100, DataType: schemapb.DataType_Int64, IsPrimaryKey: true, Name: "pk"},
+			{FieldID: 101, DataType: schemapb.DataType_FloatVector, TypeParams: []*commonpb.KeyValuePair{
+				{Key: common.DimKey, Value: "128"},
+			}},
+		},
+	}
+}
+
+func (s *WriteBufferSuite) SetupTest() {
+	s.syncMgr = syncmgr.NewMockSyncManager(s.T())
+	s.metacache = metacache.NewMockMetaCache(s.T())
+	s.wb = newWriteBufferBase(s.collSchema, s.metacache, s.syncMgr, &writeBufferOption{
+		pkStatsFactory: func(vchannel *datapb.SegmentInfo) *metacache.BloomFilterSet {
+			return metacache.NewBloomFilterSet()
+		},
+	})
+}
+
+func (s *WriteBufferSuite) TestWriteBufferType() {
+	wb, err := NewWriteBuffer(s.collSchema, s.metacache, s.syncMgr, WithDeletePolicy(DeletePolicyBFPkOracle))
+	s.NoError(err)
+
+	_, ok := wb.(*bfWriteBuffer)
+	s.True(ok)
+
+	wb, err = NewWriteBuffer(s.collSchema, s.metacache, s.syncMgr, WithDeletePolicy(DeletePolicyL0Delta), WithIDAllocator(allocator.NewMockGIDAllocator()))
+	s.NoError(err)
+	_, ok = wb.(*l0WriteBuffer)
+	s.True(ok)
+
+	_, err = NewWriteBuffer(s.collSchema, s.metacache, s.syncMgr, WithDeletePolicy(""))
+	s.Error(err)
+}
+
+func (s *WriteBufferSuite) TestHasSegment() {
+	segmentID := int64(1001)
+
+	s.False(s.wb.HasSegment(segmentID))
+
+	s.wb.getOrCreateBuffer(segmentID)
+
+	s.True(s.wb.HasSegment(segmentID))
+}
+
+func (s *WriteBufferSuite) TestFlushSegments() {
+	segmentID := int64(1001)
+
+	s.metacache.EXPECT().UpdateSegments(mock.Anything, mock.Anything, mock.Anything)
+
+	wb, err := NewWriteBuffer(s.collSchema, s.metacache, s.syncMgr, WithDeletePolicy(DeletePolicyBFPkOracle))
+	s.NoError(err)
+
+	err = wb.FlushSegments(context.Background(), []int64{segmentID})
+	s.NoError(err)
+}
+
+func TestWriteBufferBase(t *testing.T) {
+	suite.Run(t, new(WriteBufferSuite))
+}

pkg/util/merr/utils.go

@@ -525,6 +525,14 @@ func WrapErrSegmentNotFound(id int64, msg ...string) error {
 	return err
 }
 
+func WrapErrSegmentsNotFound(ids []int64, msg ...string) error {
+	err := wrapWithField(ErrSegmentNotFound, "segments", ids)
+	if len(msg) > 0 {
+		err = errors.Wrap(err, strings.Join(msg, "; "))
+	}
+	return err
+}
+
 func WrapErrSegmentNotLoaded(id int64, msg ...string) error {
 	err := wrapWithField(ErrSegmentNotLoaded, "segment", id)
 	if len(msg) > 0 {

pkg/util/paramtable/component_param.go

@@ -2419,6 +2419,7 @@ type dataNodeConfig struct {
 	FlushDeleteBufferBytes ParamItem `refreshable:"true"`
 	BinLogMaxSize          ParamItem `refreshable:"true"`
 	SyncPeriod             ParamItem `refreshable:"true"`
+	DeltaPolicy            ParamItem `refreshable:"false"`
 
 	// watchEvent
 	WatchEventTicklerInterval ParamItem `refreshable:"false"`
@@ -2548,6 +2549,15 @@ func (p *dataNodeConfig) init(base *BaseTable) {
 	}
 	p.SyncPeriod.Init(base.mgr)
 
+	p.DeltaPolicy = ParamItem{
+		Key:          "dataNode.segment.deltaPolicy",
+		Version:      "2.3.4",
+		DefaultValue: "bloom_filter_pkoracle",
+		Doc:          "the delta policy current datanode using",
+		Export:       true,
+	}
+	p.DeltaPolicy.Init(base.mgr)
+
 	p.WatchEventTicklerInterval = ParamItem{
 		Key:          "datanode.segment.watchEventTicklerInterval",
 		Version:      "2.2.3",