|
|
|
@@ -1,7 +1,7 @@
|
|
|
|
|
---
|
|
|
|
|
title: 动手写ORM框架 - GeeORM第三天 插入和查询记录
|
|
|
|
|
date: 2020-03-03 23:00:00
|
|
|
|
|
description: 7天用 Go语言/golang 从零实现 ORM 框架 GeeORM 教程(7 days implement golang object relational mapping framework from scratch tutorial)，动手写 ORM 框架，参照 gorm, xorm 的实现。实现新增(insert)记录的功能；使用反射(reflect)将数据库的记录转换为对应的结构体，实现查询(select)功能。
|
|
|
|
|
date: 2020-03-08 01:00:00
|
|
|
|
|
description: 7天用 Go语言/golang 从零实现 ORM 框架 GeeORM 教程(7 days implement golang object relational mapping framework from scratch tutorial)，动手写 ORM 框架，参照 gorm, xorm 的实现。实现新增(insert)记录的功能；使用反射(reflect)将数据库的记录转换为对应的结构体实例，实现查询(select)功能。
|
|
|
|
|
tags:
|
|
|
|
|
- Go
|
|
|
|
|
nav: 从零实现
|
|
|
|
@@ -22,4 +22,360 @@ published: false
|
|
|
|
|
本文是[7天用Go从零实现ORM框架GeeORM](https://geektutu.com/post/geeorm.html)的第三篇。
|
|
|
|
|
|
|
|
|
|
- 实现新增(insert)记录的功能。
|
|
|
|
|
- 使用反射(reflect)将数据库的记录转换为对应的结构体，实现查询(select)功能。
|
|
|
|
|
- 使用反射(reflect)将数据库的记录转换为对应的结构体实例，实现查询(select)功能。
|
|
|
|
|
|
|
|
|
|
## 1 Clause 构造 SQL 语句
|
|
|
|
|
|
|
|
|
|
从第三天开始，GeeORM 需要涉及一些较为复杂的操作，例如查询操作。查询语句一般由很多个子句(clause) 构成。SELECT 语句的构成通常是这样的：
|
|
|
|
|
|
|
|
|
|
```sql
|
|
|
|
|
SELECT col1, col2, ...
|
|
|
|
|
FROM table_name
|
|
|
|
|
WHERE [ conditions ]
|
|
|
|
|
GROUP BY col1
|
|
|
|
|
HAVING [ conditions ]
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
也就是说，如果想一次构造出完整的 SQL 语句是比较困难的，因此我们将构造 SQL 语句这一部分独立出来，放在子package clause 中实现。
|
|
|
|
|
|
|
|
|
|
首先在 `clause/generator.go` 中实现各个子句的生成规则。
|
|
|
|
|
|
|
|
|
|
[day3-save-query/clause/generator.go](https://github.com/geektutu/7days-golang/tree/master/gee-orm/day3-save-query/clause)
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
```go
|
|
|
|
|
package clause
|
|
|
|
|
|
|
|
|
|
import (
|
|
|
|
|
"fmt"
|
|
|
|
|
"strings"
|
|
|
|
|
)
|
|
|
|
|
|
|
|
|
|
type generator func(values ...interface{}) (string, []interface{})
|
|
|
|
|
|
|
|
|
|
var generators map[Type]generator
|
|
|
|
|
|
|
|
|
|
func init() {
|
|
|
|
|
generators = make(map[Type]generator)
|
|
|
|
|
generators[INSERT] = _insert
|
|
|
|
|
generators[VALUES] = _values
|
|
|
|
|
generators[SELECT] = _select
|
|
|
|
|
generators[LIMIT] = _limit
|
|
|
|
|
generators[WHERE] = _where
|
|
|
|
|
generators[ORDERBY] = _orderBy
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func genBindVars(num int) string {
|
|
|
|
|
var vars []string
|
|
|
|
|
for i := 0; i < num; i++ {
|
|
|
|
|
vars = append(vars, "?")
|
|
|
|
|
}
|
|
|
|
|
return strings.Join(vars, ", ")
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func _insert(values ...interface{}) (string, []interface{}) {
|
|
|
|
|
// INSERT INTO $tableName ($fields)
|
|
|
|
|
tableName := values[0]
|
|
|
|
|
fields := strings.Join(values[1].([]string), ",")
|
|
|
|
|
return fmt.Sprintf("INSERT INTO %s (%v)", tableName, fields), []interface{}{}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func _values(values ...interface{}) (string, []interface{}) {
|
|
|
|
|
// VALUES ($v1), ($v2), ...
|
|
|
|
|
var bindStr string
|
|
|
|
|
var sql strings.Builder
|
|
|
|
|
var vars []interface{}
|
|
|
|
|
sql.WriteString("VALUES ")
|
|
|
|
|
for i, value := range values {
|
|
|
|
|
v := value.([]interface{})
|
|
|
|
|
if bindStr == "" {
|
|
|
|
|
bindStr = genBindVars(len(v))
|
|
|
|
|
}
|
|
|
|
|
sql.WriteString(fmt.Sprintf("(%v)", bindStr))
|
|
|
|
|
if i+1 != len(values) {
|
|
|
|
|
sql.WriteString(", ")
|
|
|
|
|
}
|
|
|
|
|
vars = append(vars, v...)
|
|
|
|
|
}
|
|
|
|
|
return sql.String(), vars
|
|
|
|
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func _select(values ...interface{}) (string, []interface{}) {
|
|
|
|
|
// SELECT $fields FROM $tableName
|
|
|
|
|
tableName := values[0]
|
|
|
|
|
fields := strings.Join(values[1].([]string), ",")
|
|
|
|
|
return fmt.Sprintf("SELECT %v FROM %s", fields, tableName), []interface{}{}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func _limit(values ...interface{}) (string, []interface{}) {
|
|
|
|
|
// LIMIT $num
|
|
|
|
|
return "LIMIT ?", values
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func _where(values ...interface{}) (string, []interface{}) {
|
|
|
|
|
// WHERE $desc
|
|
|
|
|
desc, vars := values[0], values[1:]
|
|
|
|
|
return fmt.Sprintf("WHERE %s", desc), vars
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func _orderBy(values ...interface{}) (string, []interface{}) {
|
|
|
|
|
return fmt.Sprintf("ORDER BY %s", values[0]), []interface{}{}
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
然后在 `clause/clause.go` 中实现结构体 `Clause` 拼接各个独立的子句。
|
|
|
|
|
|
|
|
|
|
[day3-save-query/clause/clause.go](https://github.com/geektutu/7days-golang/tree/master/gee-orm/day3-save-query/clause)
|
|
|
|
|
|
|
|
|
|
```go
|
|
|
|
|
package clause
|
|
|
|
|
|
|
|
|
|
import "strings"
|
|
|
|
|
|
|
|
|
|
type Clause struct {
|
|
|
|
|
sql map[Type]string
|
|
|
|
|
sqlVars map[Type][]interface{}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
type Type int
|
|
|
|
|
const (
|
|
|
|
|
INSERT Type = iota
|
|
|
|
|
VALUES
|
|
|
|
|
SELECT
|
|
|
|
|
LIMIT
|
|
|
|
|
WHERE
|
|
|
|
|
ORDERBY
|
|
|
|
|
)
|
|
|
|
|
|
|
|
|
|
func (c *Clause) Set(name Type, vars ...interface{}) {
|
|
|
|
|
if c.sql == nil {
|
|
|
|
|
c.sql = make(map[Type]string)
|
|
|
|
|
c.sqlVars = make(map[Type][]interface{})
|
|
|
|
|
}
|
|
|
|
|
sql, vars := generators[name](vars...)
|
|
|
|
|
c.sql[name] = sql
|
|
|
|
|
c.sqlVars[name] = vars
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func (c *Clause) Build(orders ...Type) (string, []interface{}) {
|
|
|
|
|
var sqls []string
|
|
|
|
|
var vars []interface{}
|
|
|
|
|
for _, order := range orders {
|
|
|
|
|
if sql, ok := c.sql[order]; ok {
|
|
|
|
|
sqls = append(sqls, sql)
|
|
|
|
|
vars = append(vars, c.sqlVars[order]...)
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
return strings.Join(sqls, " "), vars
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
- `Set` 方法根据 `Type` 调用对应的 generator，生成该子句对应的 SQL 语句。
|
|
|
|
|
- `Build` 方法根据传入的 `Type` 的顺序，构造出最终的 SQL 语句。
|
|
|
|
|
|
|
|
|
|
在 `clause_test.go` 实现对应的测试用例：
|
|
|
|
|
|
|
|
|
|
```go
|
|
|
|
|
func testSelect(t *testing.T) {
|
|
|
|
|
var clause Clause
|
|
|
|
|
clause.Set(LIMIT, 3)
|
|
|
|
|
clause.Set(SELECT, "User", []string{"*"})
|
|
|
|
|
clause.Set(WHERE, "Name = ?", "Tom")
|
|
|
|
|
clause.Set(ORDERBY, "Age ASC")
|
|
|
|
|
sql, vars := clause.Build(SELECT, WHERE, ORDERBY, LIMIT)
|
|
|
|
|
t.Log(sql, vars)
|
|
|
|
|
if sql != "SELECT * FROM User WHERE Name = ? ORDER BY Age ASC LIMIT ?" {
|
|
|
|
|
t.Fatal("failed to build SQL")
|
|
|
|
|
}
|
|
|
|
|
if !reflect.DeepEqual(vars, []interface{}{"Tom", 3}) {
|
|
|
|
|
t.Fatal("failed to build SQLVars")
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func TestClause_Build(t *testing.T) {
|
|
|
|
|
t.Run("select", func(t *testing.T) {
|
|
|
|
|
testSelect(t)
|
|
|
|
|
})
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
## 2 实现 Insert 功能
|
|
|
|
|
|
|
|
|
|
clause 已经支持生成简单的插入(INSERT) 和 查询(SELECT) 的 SQL 语句，那么紧接着我们就可以在 session 中实现对应的功能了。
|
|
|
|
|
|
|
|
|
|
INSERT 对应的 SQL 语句一般是这样的：
|
|
|
|
|
|
|
|
|
|
```sql
|
|
|
|
|
INSERT INTO table_name(col1, col2, col3, ...) VALUES
|
|
|
|
|
(A1, A2, A3, ...),
|
|
|
|
|
(B1, B2, B3, ...),
|
|
|
|
|
...
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
在 ORM 框架中期望 Insert 的调用方式如下：
|
|
|
|
|
|
|
|
|
|
```go
|
|
|
|
|
s := geeorm.NewEngine().NewSession()
|
|
|
|
|
u1 := &User{Name: "Tom", Age: 18}
|
|
|
|
|
u2 := &User{Name: "Sam", Age: 25}
|
|
|
|
|
s.Insert(u1, u2, ...)
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
也就是说，我们还需要一个步骤，根据数据库中列的顺序，从对象中找到对应的值，按顺序平铺。即 `u1`、`u2` 转换为 `("Tom", 18), ("Same", 25)` 这样的格式。
|
|
|
|
|
|
|
|
|
|
因此在实现 Insert 功能之前，还需要给 `Schema` 新增一个函数 `RecordValues` 完成上述的转换。
|
|
|
|
|
|
|
|
|
|
[day3-save-query/schema/schema.go](https://github.com/geektutu/7days-golang/tree/master/gee-orm/day3-save-query/schema)
|
|
|
|
|
|
|
|
|
|
```go
|
|
|
|
|
func (schema *Schema) RecordValues(dest interface{}) []interface{} {
|
|
|
|
|
destValue := reflect.Indirect(reflect.ValueOf(dest))
|
|
|
|
|
var fieldValues []interface{}
|
|
|
|
|
for _, field := range schema.Fields {
|
|
|
|
|
fieldValues = append(fieldValues, destValue.FieldByName(field.Name).Interface())
|
|
|
|
|
}
|
|
|
|
|
return fieldValues
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
在 session 文件夹下新建 record.go，用于实现记录增删查改相关的代码。
|
|
|
|
|
|
|
|
|
|
[day3-save-query/session/record.go](https://github.com/geektutu/7days-golang/tree/master/gee-orm/day3-save-query/session)
|
|
|
|
|
|
|
|
|
|
```go
|
|
|
|
|
package session
|
|
|
|
|
|
|
|
|
|
import (
|
|
|
|
|
"geeorm/clause"
|
|
|
|
|
"reflect"
|
|
|
|
|
)
|
|
|
|
|
|
|
|
|
|
func (s *Session) Insert(values ...interface{}) (int64, error) {
|
|
|
|
|
recordValues := make([]interface{}, 0)
|
|
|
|
|
for _, value := range values {
|
|
|
|
|
table := s.Model(value).RefTable()
|
|
|
|
|
s.clause.Set(clause.INSERT, table.Name, table.FieldNames)
|
|
|
|
|
recordValues = append(recordValues, table.RecordValues(value))
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
s.clause.Set(clause.VALUES, recordValues...)
|
|
|
|
|
sql, vars := s.clause.Build(clause.INSERT, clause.VALUES)
|
|
|
|
|
result, err := s.Raw(sql, vars...).Exec()
|
|
|
|
|
if err != nil {
|
|
|
|
|
return 0, err
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
return result.RowsAffected()
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
后续所有构造 SQL 语句的方式都将与 `Insert` 中构造 SQL 语句的方式一致。分两步：
|
|
|
|
|
|
|
|
|
|
- 1）多次调用 `clause.Set()` 构造好每一个子句。
|
|
|
|
|
- 2）调用一次 `clause.Build()` 按照传入的顺序构造出最终的 SQL 语句。
|
|
|
|
|
|
|
|
|
|
构造完成后，调用 `Raw().Exec()` 方法执行。
|
|
|
|
|
|
|
|
|
|
## 3 实现 Find 功能
|
|
|
|
|
|
|
|
|
|
期望的调用方式是这样的：传入一个切片指针，查询的结果保存在切片中。
|
|
|
|
|
|
|
|
|
|
```go
|
|
|
|
|
s := geeorm.NewEngine().NewSession()
|
|
|
|
|
var users []User
|
|
|
|
|
s.Find(&users);
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
Find 功能的难点和 Insert 恰好反了过来。Insert 需要将已经存在的对象的每一个字段的值平铺开来，而 Find 则是需要根据平铺开的字段的值构造出对象。同样，也需要用到反射(reflect)。
|
|
|
|
|
|
|
|
|
|
```go
|
|
|
|
|
func (s *Session) Find(values interface{}) error {
|
|
|
|
|
destSlice := reflect.Indirect(reflect.ValueOf(values))
|
|
|
|
|
destType := destSlice.Type().Elem()
|
|
|
|
|
table := s.Model(reflect.New(destType).Elem().Interface()).RefTable()
|
|
|
|
|
|
|
|
|
|
s.clause.Set(clause.SELECT, table.Name, table.FieldNames)
|
|
|
|
|
sql, vars := s.clause.Build(clause.SELECT, clause.WHERE, clause.ORDERBY, clause.LIMIT)
|
|
|
|
|
rows, err := s.Raw(sql, vars...).QueryRows()
|
|
|
|
|
if err != nil {
|
|
|
|
|
return err
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
for rows.Next() {
|
|
|
|
|
dest := reflect.New(destType).Elem()
|
|
|
|
|
var values []interface{}
|
|
|
|
|
for _, name := range table.FieldNames {
|
|
|
|
|
values = append(values, dest.FieldByName(name).Addr().Interface())
|
|
|
|
|
}
|
|
|
|
|
if err := rows.Scan(values...); err != nil {
|
|
|
|
|
return err
|
|
|
|
|
}
|
|
|
|
|
destSlice.Set(reflect.Append(destSlice, dest))
|
|
|
|
|
}
|
|
|
|
|
return rows.Close()
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
Find 的代码实现比较复杂，主要分为以下几步：
|
|
|
|
|
|
|
|
|
|
- 1) `destSlice.Type().Elem()` 获取切片的单个元素的类型 `destType`，使用 `reflect.New()` 方法创建一个 `destType` 的实例，作为 `Model()` 的入参，映射出表结构 `RefTable()`。
|
|
|
|
|
- 2）根据表结构，使用 clause 构造出 SELECT 语句，查询到所有符合条件的记录 `rows`。
|
|
|
|
|
- 3）遍历每一行记录，利用反射创建 `destType` 的实例 `dest`，将 `dest` 的所有字段平铺开，构造切片 `values`。
|
|
|
|
|
- 4）调用 `rows.Scan()` 将该行记录每一列的值依次赋值给 values 中的每一个字段。
|
|
|
|
|
- 5）将 `dest` 添加到切片 `destSlice` 中。循环直到所有的记录都添加到切片 `destSlice` 中。
|
|
|
|
|
|
|
|
|
|
## 4 测试
|
|
|
|
|
|
|
|
|
|
在 session 文件夹下新建 `record_test.go`，创建测试用例。
|
|
|
|
|
|
|
|
|
|
> `User` 和 `NewSession()` 的定义位于 raw_test.go 中。
|
|
|
|
|
|
|
|
|
|
[day3-save-query/session/record_test.go](https://github.com/geektutu/7days-golang/tree/master/gee-orm/day3-save-query/session)
|
|
|
|
|
|
|
|
|
|
```go
|
|
|
|
|
package session
|
|
|
|
|
|
|
|
|
|
import "testing"
|
|
|
|
|
|
|
|
|
|
var (
|
|
|
|
|
user1 = &User{"Tom", 18}
|
|
|
|
|
user2 = &User{"Sam", 25}
|
|
|
|
|
user3 = &User{"Jack", 25}
|
|
|
|
|
)
|
|
|
|
|
|
|
|
|
|
func testRecordInit(t *testing.T) *Session {
|
|
|
|
|
t.Helper()
|
|
|
|
|
s := NewSession().Model(&User{})
|
|
|
|
|
err1 := s.DropTable()
|
|
|
|
|
err2 := s.CreateTable()
|
|
|
|
|
_, err3 := s.Insert(user1, user2)
|
|
|
|
|
if err1 != nil || err2 != nil || err3 != nil {
|
|
|
|
|
t.Fatal("failed init test records")
|
|
|
|
|
}
|
|
|
|
|
return s
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func TestSession_Insert(t *testing.T) {
|
|
|
|
|
s := testRecordInit(t)
|
|
|
|
|
affected, err := s.Insert(user3)
|
|
|
|
|
if err != nil || affected != 1 {
|
|
|
|
|
t.Fatal("failed to create record")
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
func TestSession_Find(t *testing.T) {
|
|
|
|
|
s := testRecordInit(t)
|
|
|
|
|
var users []User
|
|
|
|
|
if err := s.Find(&users); err != nil || len(users) != 2 {
|
|
|
|
|
t.Fatal("failed to query all")
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
## 附 推荐阅读
|
|
|
|
|
|
|
|
|
|
- [Go 语言简明教程](https://geektutu.com/post/quick-golang.html)
|
|
|
|
|
- [Go Test 单元测试简明教程](https://geektutu.com/post/quick-go-test.html)
|
|
|
|
|
- [SQLite 常用命令速查表](https://geektutu.com/post/cheat-sheet-sqlite.html)
|
|
|
|
|
- [Laws Of Reflection - golang.org](https://blog.golang.org/laws-of-reflection)
|
gzdaijie