fix issue #1530

database/gdb/gdb_core_structure.go

@@ -218,7 +218,7 @@ func (c *Core) convertFieldValueToLocalValue(fieldValue interface{}, fieldType s
 // mappingAndFilterData automatically mappings the map key to table field and removes
 // all key-value pairs that are not the field of given table.
 func (c *Core) mappingAndFilterData(schema, table string, data map[string]interface{}, filter bool) (map[string]interface{}, error) {
-	fieldsMap, err := c.db.TableFields(c.GetCtx(), c.guessPrimaryTableName(table), schema)
+	fieldsMap, err := c.TableFields(c.guessPrimaryTableName(table), schema)
 	if err != nil {
 		return nil, err
 	}

database/gdb/gdb_core_utility.go

@@ -90,19 +90,23 @@ func (c *Core) Tables(schema ...string) (tables []string, err error) {
 // TableFields retrieves and returns the fields' information of specified table of current schema.
 //
 // Note that it returns a map containing the field name and its corresponding fields.
-// As a map is unsorted, the TableField struct has a "Index" field marks its sequence in the fields.
+// As a map is unsorted, the TableField struct has an "Index" field marks its sequence in the fields.
 //
 // It's using cache feature to enhance the performance, which is never expired util the process restarts.
 //
 // It does nothing in default.
 func (c *Core) TableFields(table string, schema ...string) (fields map[string]*TableField, err error) {
-	return
+	// It does nothing if given table is empty, especially in sub-query.
+	if table == "" {
+		return map[string]*TableField{}, nil
+	}
+	return c.db.TableFields(c.GetCtx(), table, schema...)
 }
 
 // HasField determine whether the field exists in the table.
 func (c *Core) HasField(table, field string, schema ...string) (bool, error) {
 	table = c.guessPrimaryTableName(table)
-	tableFields, err := c.db.TableFields(c.GetCtx(), table, schema...)
+	tableFields, err := c.TableFields(table, schema...)
 	if err != nil {
 		return false, err
 	}

database/gdb/gdb_driver_mysql.go

@@ -128,7 +128,10 @@ func (d *DriverMysql) TableFields(ctx context.Context, table string, schema ...s
 	charL, charR := d.GetChars()
 	table = gstr.Trim(table, charL+charR)
 	if gstr.Contains(table, " ") {
-		return nil, gerror.NewCode(gcode.CodeInvalidParameter, "function TableFields supports only single table operations")
+		return nil, gerror.NewCode(
+			gcode.CodeInvalidParameter,
+			"function TableFields supports only single table operations",
+		)
 	}
 	useSchema := d.schema.Val()
 	if len(schema) > 0 && schema[0] != "" {
@@ -144,7 +147,10 @@ func (d *DriverMysql) TableFields(ctx context.Context, table string, schema ...s
 			if link, err = d.SlaveLink(useSchema); err != nil {
 				return nil
 			}
-			result, err = d.DoGetAll(ctx, link, fmt.Sprintf(`SHOW FULL COLUMNS FROM %s`, d.QuoteWord(table)))
+			result, err = d.DoGetAll(
+				ctx, link,
+				fmt.Sprintf(`SHOW FULL COLUMNS FROM %s`, d.QuoteWord(table)),
+			)
 			if err != nil {
 				return nil
 			}

database/gdb/gdb_model_utility.go

@@ -31,15 +31,14 @@ func (m *Model) QuoteWord(s string) string {
 //
 // Also see DriverMysql.TableFields.
 func (m *Model) TableFields(tableStr string, schema ...string) (fields map[string]*TableField, err error) {
-	useSchema := m.schema
+	var (
+		table     = m.db.GetCore().guessPrimaryTableName(tableStr)
+		useSchema = m.schema
+	)
 	if len(schema) > 0 && schema[0] != "" {
 		useSchema = schema[0]
 	}
-	return m.db.TableFields(
-		m.GetCtx(),
-		m.db.GetCore().guessPrimaryTableName(tableStr),
-		useSchema,
-	)
+	return m.db.GetCore().TableFields(table, useSchema)
 }
 
 // getModel creates and returns a cloned model of current model if `safe` is true, or else it returns