enhance: [GoSDK] Add reciever parse result cache (#44166)

Related to #44161

This PR:
- Add reciever parse result cache
- Fix for nil IDs unmarshal panicking (#42895)

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>
Co-authored-by: wangcanjia <phpip@qq.com>

client/milvusclient/results.go

@@ -86,6 +86,9 @@ func (sr *ResultSet) Unmarshal(receiver any) (err error) {
 	if err != nil {
 		return err
 	}
+	if sr.IDs == nil {
+		return nil
+	}
 	return sr.fillPKEntry(receiver)
 }
 
@@ -116,8 +119,8 @@ func (sr *ResultSet) fillPKEntry(receiver any) (err error) {
 			et = et.Elem()
 		}
 
-		candidates := row.ParseCandidate(et)
-		candi, ok := candidates[pkField.Name]
+		rc := row.GetReceiverCandidate(et)
+		candi, ok := rc.Name2FieldIndex(pkField.Name)
 		if !ok {
 			// pk field not found in struct, skip
 			return nil
@@ -202,10 +205,10 @@ func (ds DataSet) Unmarshal(receiver any) (err error) {
 }
 
 func (ds DataSet) fillData(data reflect.Value, dataType reflect.Type, idx int) error {
-	m := row.ParseCandidate(dataType)
+	rc := row.GetReceiverCandidate(dataType)
 	for i := 0; i < len(ds); i++ {
 		name := ds[i].Name()
-		fidx, ok := m[name]
+		fidx, ok := rc.Name2FieldIndex(name)
 		if !ok {
 			// if target is not found, the behavior here is to ignore the column
 			// `strict` mode could be added in the future to return error if any column missing

client/row/cache.go

@@ -0,0 +1,45 @@
+// 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 row
+
+import (
+	"reflect"
+
+	"github.com/milvus-io/milvus/pkg/v2/util/typeutil"
+)
+
+var cachedCandidates *typeutil.ConcurrentMap[reflect.Type, *ReceiverCandidate]
+
+func init() {
+	cachedCandidates = typeutil.NewConcurrentMap[reflect.Type, *ReceiverCandidate]()
+}
+
+func GetReceiverCandidate(v reflect.Type) *ReceiverCandidate {
+	rc, ok := cachedCandidates.Get(v)
+	if ok {
+		return rc
+	}
+
+	// reflect.Type.String() cannot work as unique identifier for singleflight
+	// accept multiple parse for now
+	rc = &ReceiverCandidate{
+		name2Index: parseCandidate(v),
+	}
+	cachedCandidates.Insert(v, rc)
+
+	return rc
+}

client/row/type.go

@@ -21,7 +21,19 @@ import (
 	"reflect"
 )
 
-func ParseCandidate(dataType reflect.Type) map[string]int {
+// ReceiverCandidate is the struct stores the information needed for
+// receiver setting when unmarshalling dataset to user defined struct
+type ReceiverCandidate struct {
+	name2Index map[string]int
+}
+
+func (rc *ReceiverCandidate) Name2FieldIndex(fieldName string) (int, bool) {
+	// lock not needed, read ops only
+	index, ok := rc.name2Index[fieldName]
+	return index, ok
+}
+
+func parseCandidate(dataType reflect.Type) map[string]int {
 	result := make(map[string]int)
 	for i := 0; i < dataType.NumField(); i++ {
 		f := dataType.Field(i)