From 1e3ec42e548acbd211d880a513e033fa7cb76693 Mon Sep 17 00:00:00 2001
From: congqixia <congqi.xia@zilliz.com>
Date: Wed, 17 Sep 2025 11:36:00 +0800
Subject: [PATCH] fix: Check child fields len instead of nil (#44405)

Related to #44398

---------

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>
---
 internal/flushcommon/metacache/segment.go       |  5 +++++
 internal/flushcommon/syncmgr/task.go            | 11 +++++++----
 internal/storagecommon/column_group_splitter.go |  5 +++++
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/internal/flushcommon/metacache/segment.go b/internal/flushcommon/metacache/segment.go
index b5880fb117..6d0caae8af 100644
--- a/internal/flushcommon/metacache/segment.go
+++ b/internal/flushcommon/metacache/segment.go
@@ -17,11 +17,14 @@
 package metacache
 
 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/flushcommon/metacache/pkoracle"
 	"github.com/milvus-io/milvus/internal/storage"
 	"github.com/milvus-io/milvus/internal/storagecommon"
+	"github.com/milvus-io/milvus/pkg/v2/log"
 	"github.com/milvus-io/milvus/pkg/v2/proto/datapb"
 )
 
@@ -146,6 +149,7 @@ func (s *SegmentInfo) Clone() *SegmentInfo {
 		statslogs:        s.statslogs,
 		deltalogs:        s.deltalogs,
 		bm25logs:         s.bm25logs,
+		currentSplit:     s.currentSplit,
 	}
 }
 
@@ -165,6 +169,7 @@ func NewSegmentInfo(info *datapb.SegmentInfo, bfs pkoracle.PkStat, bm25Stats *Se
 				Fields:  group.GetChildFields(),
 			})
 		}
+		log.Info("recover split info", zap.Int64("segmentID", info.GetID()), zap.Stringers("columnGroup", currentSplit))
 	}
 	return &SegmentInfo{
 		segmentID:        info.GetID(),
diff --git a/internal/flushcommon/syncmgr/task.go b/internal/flushcommon/syncmgr/task.go
index 9c98456f7b..ca32ffac00 100644
--- a/internal/flushcommon/syncmgr/task.go
+++ b/internal/flushcommon/syncmgr/task.go
@@ -220,8 +220,10 @@ func (t *SyncTask) getColumnGroups(segmentInfo *metacache.SegmentInfo) []storage
 	if currentSplit := segmentInfo.GetCurrentSplit(); currentSplit != nil {
 		for _, cg := range currentSplit {
 			// legacy split found, use legacy policy
-			if cg.Fields == nil {
-				return storagecommon.SplitColumns(allFields, map[int64]storagecommon.ColumnStats{}, storagecommon.NewSelectedDataTypePolicy(), storagecommon.NewRemanentShortPolicy(-1))
+			if len(cg.Fields) == 0 {
+				result := storagecommon.SplitColumns(allFields, map[int64]storagecommon.ColumnStats{}, storagecommon.NewSelectedDataTypePolicy(), storagecommon.NewRemanentShortPolicy(-1))
+				log.Info("use legacy split policy", zap.Int64("segmentID", t.segmentID), zap.Stringers("columnGroups", result))
+				return result
 			}
 		}
 		field2idx := make(map[int64]int)
@@ -237,9 +239,10 @@ func (t *SyncTask) getColumnGroups(segmentInfo *metacache.SegmentInfo) []storage
 		return currentSplit
 	}
 
-	// TODO calculate field stats
 	policies := storagecommon.DefaultPolicies()
-	return storagecommon.SplitColumns(allFields, t.calcColumnStats(), policies...)
+	result := storagecommon.SplitColumns(allFields, t.calcColumnStats(), policies...)
+	log.Info("sync new split columns", zap.Int64("segmentID", t.segmentID), zap.Stringers("columnGroups", result))
+	return result
 }
 
 func (t *SyncTask) calcColumnStats() map[int64]storagecommon.ColumnStats {
diff --git a/internal/storagecommon/column_group_splitter.go b/internal/storagecommon/column_group_splitter.go
index 0facb45066..404916e14f 100644
--- a/internal/storagecommon/column_group_splitter.go
+++ b/internal/storagecommon/column_group_splitter.go
@@ -17,6 +17,7 @@
 package storagecommon
 
 import (
+	"fmt"
 	"sort"
 
 	"github.com/milvus-io/milvus-proto/go-api/v2/schemapb"
@@ -35,6 +36,10 @@ type ColumnGroup struct {
 	Fields  []int64
 }
 
+func (cg ColumnGroup) String() string {
+	return fmt.Sprintf("[GroupID: %d, ColumnIndices: %v, Fields: %v]", cg.GroupID, cg.Columns, cg.Fields)
+}
+
 func SplitColumns(fields []*schemapb.FieldSchema, stats map[int64]ColumnStats, policies ...ColumnGroupSplitPolicy) []ColumnGroup {
 	split := newCurrentSplit(fields, stats)
 	for _, policy := range policies {