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为: https://gitea.com/xorm/xorm/issues/2243）

session.go

@@ -393,10 +393,10 @@ func (session *Session) doPrepareTx(sqlStr string) (stmt *core.Stmt, err error)
 	return
 }
 
-func getField(dataStruct *reflect.Value, table *schemas.Table, colName string, idx int) (*schemas.Column, *reflect.Value, error) {
+func getField(dataStruct *reflect.Value, table *schemas.Table, field *QueryedField) (*schemas.Column, *reflect.Value, error) {
-	col := table.GetColumnIdx(colName, idx)
+	col := field.ColumnSchema
 	if col == nil {
-		return nil, nil, ErrFieldIsNotExist{colName, table.Name}
+		return nil, nil, ErrFieldIsNotExist{field.FieldName, table.Name}
 	}
 
 	fieldValue, err := col.ValueOfV(dataStruct)
@@ -404,10 +404,10 @@ func getField(dataStruct *reflect.Value, table *schemas.Table, colName string, i
 		return nil, nil, err
 	}
 	if fieldValue == nil {
-		return nil, nil, ErrFieldIsNotValid{colName, table.Name}
+		return nil, nil, ErrFieldIsNotValid{field.FieldName, table.Name}
 	}
 	if !fieldValue.IsValid() || !fieldValue.CanSet() {
-		return nil, nil, ErrFieldIsNotValid{colName, table.Name}
+		return nil, nil, ErrFieldIsNotValid{field.FieldName, table.Name}
 	}
 
 	return col, fieldValue, nil
@@ -712,7 +712,7 @@ func (session *Session) slice2Bean(scanResults []interface{}, allColum *AllColum
 
 	var pk schemas.PK
 	for i, field := range allColum.Fields {
-		col, fieldValue, err := getField(dataStruct, table, field.FieldName, field.TempIndex)
+		col, fieldValue, err := getField(dataStruct, table, field)
 		if _, ok := err.(ErrFieldIsNotExist); ok {
 			continue
 		} else if err != nil {

session_find.go

@@ -168,6 +168,7 @@ type QueryedField struct {
 	LowerFieldName string
 	ColumnType     *sql.ColumnType
 	TempIndex      int
+	ColumnSchema   *schemas.Column
 }
 
 type AllColumn struct {
@@ -176,6 +177,19 @@ type AllColumn struct {
 	Types      []*sql.ColumnType
 }
 
+func (allColumn *AllColumn) ParseTableSchema(table *schemas.Table) error {
+	for _, field := range allColumn.Fields {
+		col := table.GetColumnIdx(field.FieldName, field.TempIndex)
+		if col == nil {
+			return ErrFieldIsNotExist{FieldName: field.FieldName, TableName: table.Name}
+		}
+
+		field.ColumnSchema = col
+	}
+
+	return nil
+}
+
 func ParseQueryRows(fieldNames []string, types []*sql.ColumnType) *AllColumn {
 	var allColumn AllColumn
 
@@ -289,6 +303,12 @@ func (session *Session) noCacheFind(table *schemas.Table, containerValue reflect
 		if err != nil {
 			return err
 		}
+
+		parseTableSchemaError := allColumn.ParseTableSchema(tb)
+		if parseTableSchemaError != nil {
+			return parseTableSchemaError
+		}
+
 		err = session.rows2Beans(rows, allColumn, fields, types, tb, newElemFunc, containerValueSetFunc)
 		rows.Close()
 		if err != nil {