gdb/gdb_core: issue title When cross-database query is not done using Schema, the corresponding table structure fields cannot be obtained correctly; if you want to add a parameter, you can directly use data as the table field.

[yimuysl001]

Description

不使用Schema 跨库查询时（使用事务时无法正确切换到相应的库），无法正确获取到相应的表结构字段；希望添加一个参数，可以直接使用data作为表字段

	_, err := g.DB("local").Model("BAK..TBA").Data(map[string]interface{}{
		"id":   2,
		"name": "aaa",
	}).Insert()
	fmt.Println(err) //报错 The table "BAK".."TBA" may not exist, or the table contains no fields
	_, err = g.DB("local").Schema("BAK").Model("TBA").Data(map[string]interface{}{
		"id":   2,
		"name": "aaa",
	}).Insert()
	fmt.Println(err) //处理成功

Additional

func (c *Core) mappingAndFilterData(ctx context.Context, schema, table string, data map[string]interface{}, filter bool) (map[string]interface{}, error) {
    
    // 是否可以直接从table中把 schema 拆出来，
	fieldsMap, err := c.db.TableFields(ctx, c.guessPrimaryTableName(table), schema)
	if err != nil {
		return nil, err
	}
   
 
	if len(fieldsMap) == 0 {
         // 或者没查到数据使用data的key ,而不是直接报错
        
		return nil, gerror.Newf(`The table %s may not exist, or the table contains no fields`, table)
	}
	fieldsKeyMap := make(map[string]interface{}, len(fieldsMap))
	for k := range fieldsMap {
		fieldsKeyMap[k] = nil
	}
	// Automatic data key to table field name mapping.
	var foundKey string
	for dataKey, dataValue := range data {
		if _, ok := fieldsKeyMap[dataKey]; !ok {
			foundKey, _ = gutil.MapPossibleItemByKey(fieldsKeyMap, dataKey)
			if foundKey != "" {
				if _, ok = data[foundKey]; !ok {
					data[foundKey] = dataValue
				}
				delete(data, dataKey)
			}
		}
	}
	// Data filtering.
	// It deletes all key-value pairs that has incorrect field name.
	if filter {
		for dataKey := range data {
			if _, ok := fieldsMap[dataKey]; !ok {
				delete(data, dataKey)
			}
		}
		if len(data) == 0 {
			return nil, gerror.Newf(`input data match no fields in table %s`, table)
		}
	}
	return data, nil
}



func (c *Core) fieldsToSequence(ctx context.Context, table string, fields []string) ([]string, error) {
	var (
		fieldSet               = gset.NewStrSetFrom(fields)
		fieldsResultInSequence = make([]string, 0)
		tableFields, err       = c.db.TableFields(ctx, table)
	)
	if err != nil {
		return nil, err
	}
     /****/
    // todo 希望如果没查询到字段，能返回fields
    if len(tableFields)<1 {
        return fields,nil
    }
    /****/
	// Sort the fields in order.
	var fieldsOfTableInSequence = make([]string, len(tableFields))
	for _, field := range tableFields {
		fieldsOfTableInSequence[field.Index] = field.Name
	}
	// Sort the input fields.
	for _, fieldName := range fieldsOfTableInSequence {
		if fieldSet.Contains(fieldName) {
			fieldsResultInSequence = append(fieldsResultInSequence, fieldName)
		}
	}
	return fieldsResultInSequence, nil
}

[gqcn]

@yimuysl001 您好，我们很喜欢你的建议，麻烦提交一下完整的最小可运行代码呢，如果评估可以开发，我们可以拿来作为单测验证。

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@yimuysl001 Hello, we like your suggestion very much. Please submit the complete minimum runnable code. If the evaluation can be developed, we can use it as a single test verification.

[yimuysl001]

@gqcn 已提交pr

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@gqcn has submitted PR