diff --git a/go-api/commonpb/common.pb.go b/go-api/commonpb/common.pb.go
index 4be5a6f4..0189bac3 100644
--- a/go-api/commonpb/common.pb.go
+++ b/go-api/commonpb/common.pb.go
@@ -1275,9 +1275,9 @@ func (m *Blob) GetValue() []byte {
 type PlaceholderValue struct {
 	Tag  string          `protobuf:"bytes,1,opt,name=tag,proto3" json:"tag,omitempty"`
 	Type PlaceholderType `protobuf:"varint,2,opt,name=type,proto3,enum=milvus.proto.common.PlaceholderType" json:"type,omitempty"`
-	// dense vector: values is a 2d-array of nq rows, every row contains a query vector
-	// sparse vector: values contains exactly 1 bytes array, which is the byte
-	// representation of SparseFloatArray in schema.proto
+	// values is a 2d-array of nq rows, every row contains a query vector.
+	// for dense vector, all rows are of the same length; for sparse vector,
+	// the length of each row may vary depending on their number of non-zeros.
 	Values               [][]byte `protobuf:"bytes,3,rep,name=values,proto3" json:"values,omitempty"`
 	XXX_NoUnkeyedLiteral struct{} `json:"-"`
 	XXX_unrecognized     []byte   `json:"-"`
diff --git a/proto/common.proto b/proto/common.proto
index 583cc287..af0c3459 100644
--- a/proto/common.proto
+++ b/proto/common.proto
@@ -138,9 +138,9 @@ enum PlaceholderType {
 message PlaceholderValue {
     string tag = 1;
     PlaceholderType type = 2;
-    // dense vector: values is a 2d-array of nq rows, every row contains a query vector
-    // sparse vector: values contains exactly 1 bytes array, which is the byte
-    // representation of SparseFloatArray in schema.proto
+    // values is a 2d-array of nq rows, every row contains a query vector.
+    // for dense vector, all rows are of the same length; for sparse vector,
+    // the length of each row may vary depending on their number of non-zeros.
     repeated bytes values = 3;
 }