优化func (session *Session) slice2Bean方法中的strings.ToLower以及减少map创建和访问次数（对应issue:https://gitea.com/xorm/xorm/issues/2243）

session.go

@@ -710,20 +710,9 @@ func (session *Session) slice2Bean(scanResults []interface{}, allColum *AllColum
 
 	buildAfterProcessors(session, bean)
 
-	tempMap := make(map[string]int)
 	var pk schemas.PK
 	for i, field := range allColum.Fields {
-		var idx int
+		col, fieldValue, err := getField(dataStruct, table, field.FieldName, field.TempIndex)
-		var ok bool
-
-		if idx, ok = tempMap[field.LowerFieldName]; !ok {
-			idx = 0
-		} else {
-			idx++
-		}
-		tempMap[field.LowerFieldName] = idx
-
-		col, fieldValue, err := getField(dataStruct, table, field.FieldName, idx)
 		if _, ok := err.(ErrFieldIsNotExist); ok {
 			continue
 		} else if err != nil {

session_find.go

@@ -167,6 +167,7 @@ type QueryedField struct {
 	FieldName      string
 	LowerFieldName string
 	ColumnType     *sql.ColumnType
+	TempIndex      int
 }
 
 type AllColumn struct {
@@ -190,6 +191,22 @@ func ParseQueryRows(fieldNames []string, types []*sql.ColumnType) *AllColumn {
 	}
 
 	allColumn.Fields = fields
+
+	tempMap := make(map[string]int)
+	for _, field := range fields {
+		var idx int
+		var ok bool
+
+		if idx, ok = tempMap[field.LowerFieldName]; !ok {
+			idx = 0
+		} else {
+			idx++
+		}
+
+		tempMap[field.LowerFieldName] = idx
+		field.TempIndex = idx
+	}
+
 	return &allColumn
 }