/*表结构*/
CREATE TABLE public.user
(
 id serial primary key,
 name varchar(20)
);
ALTER TABLE public.user ADD COLUMN created timestamp default now();
ALTER TABLE public.user ADD COLUMN class_id integer default 1;
insert into public.user(name) values('ft');
insert into public.user(name) values('ft2');
insert into public.user(name,class_id) values('ft8',2)
CREATE TABLE public.class
(
 id serial primary key,
 name varchar(20)
);
insert into public.class(name) values('高中一班');
insert into public.class(name) values('高中二班');
/*常用到的操作*/
select * from public.class;
select * from public.user;
select u.id,u.name,c.name from public.user as u left join public.class as c on u.class_id=c.id;

package main
import (
 _ "github.com/lib/pq"
 "github.com/xormplus/xorm"
 "fmt"
 "time"
 "strconv"
)
//用户表结构
type User struct {
 Id  int  `xorm:"not null pk autoincr INTEGER"`
 Name string `xorm:"VARCHAR(20)"`
 Created time.Time `xorm:"default 'now()' DATETIME"`
 ClassId int  `xorm:"default 1 INTEGER"`
}
//Class表结构
type Class struct {
 Id int `xorm:"not null pk autoincr INTEGER"`
 Name string `xorm:"VARCHAR(20)"`
}
//临时表结构
type UserClass struct{
 User `xorm:"extends"`
 Name string
}
//此方法仅用于orm查询时，查询表认定
func (UserClass) TableName() string {
 return "public.user"
}
func main() {
 //1.创建db引擎
 db, err := xorm.NewPostgreSQL("postgres://postgres:123@localhost:5432/test?sslmode=disable")
 if err != nil {
  fmt.Println(err)
 }
 //2.显示sql语句
 db.ShowSQL(true)
 //3.设置连接数
 db.SetMaxIdleConns(2000)
 db.SetMaxOpenConns(1000)
 cacher := xorm.NewLRUCacher(xorm.NewMemoryStore(), 500)//缓存的条数
 db.SetDefaultCacher(cacher)
 //4.执行插入语句的几种方式
  //4.1 orm插入方式:不好控制，如果仅仅插入的对象的属性是name='ftq',那么其他的零值会一同insert，orm方式对零值的处理有点不太好
  if false {
   user := new(User)
   user.Name = "ftq"
   _, err = db.Insert(user)
   if err != nil {
    fmt.Println(err)
   }
  }
  //4.2 命令插入方式
   //4.2.1 db.Exec():单事务单次提交
   if false{
   sql:="insert into public.user(name) values(?)"
   db.Exec(sql,"ft4")
   }
   //4.2.2 db.SQL().Execute():单事务准备了Statement处理sql语句
   if false{
    sql:="insert into public.user(name) values(?)"
    db.SQL(sql,"ft5").Execute()
   }
   //4.2.3使用sql配置文件管理语句,两种载入配置的方式LoadSqlMap()和RegisterSqlMap(),以及SqlMapClient()替代SQL()
   if false {
    err = db.LoadSqlMap("./sql.xml")
    //err = db.RegisterSqlMap(xorm.Xml("./","sql.xml"))
    if err != nil {
     fmt.Println(err)
    }
    db.SqlMapClient("insert_1","ft7").Execute()
   }
 //5.执行查询的几种方式
  //5.1 orm查询:在user初始化的时候,该orm查询直接通过扫描user类型确定表名;组合使用Where(),Get()
  if false {
   user := new(User)
   boolget ,err2 :=db.Where("id=?",5).Get(user)
   fmt.Println(boolget,err2,user)
  }
  //5.2 orm查询:组合使用Where(),Get(),And()
  if false {
   user := new(User)
   boolget ,err2 :=db.Where("id=?",5).And("name=?","ft7").And("id>?",3).Get(user)
   fmt.Println(boolget,err2,user)
  }
  //5.3 orm查询: AllCols()查询所有列，Cols()查询部分列，Find()解析多行结果,Get()解析单行结果
  if false {
   users := new ([]User)
   err = db.AllCols().Find(users)
   //err = db.Cols("id","name").Find(users)
   if err !=nil {
    fmt.Println(err)
   }
   fmt.Println(users)
  }
  //5.4 orm查询:连接查询Join()
  if false {
   users := new([]UserClass)
   db.Join("INNER","class","user.class_id=class.id").Find(users)
   //db.SQL("select u.id,u.name,c.name from public.user as u left join public.class as c on u.class_id=c.id").Find(users)
   fmt.Println(users)
  }
  //5.5 sql查询略
  if false {
   //和insert类似,Find查找多行结果，Get获取 单行结果
   users := new([]UserClass)
   db.SQL("select u.id,u.name,c.name from public.user as u left join public.class as c on u.class_id=c.id").Find(users)
   fmt.Println(users)
   }
  //5.6 链式查找
  if false {
   //值得一提的是，支持查找某行的某个字段，不过一般在sql语句中就可以完成过滤，如果sql语句过于复杂，可以链式查找过滤
   id := db.SQL("select * from public.user").Query().Results[0]["id"]
   fmt.Println(id)
  }
 //6.执行更新
  //6.1 ORM方式: 只有非0值的属性会被更新，user的id和created都是默认零值，不被处理
  if false {
   user :=new(User)
   user.Name="ftx"
   //[xorm] [info] 2018/02/08 12:04:01.330624 [SQL] UPDATE "user" SET "name" = $1 WHERE "id"=$2 []interface {}{"ftx", 4}
   db.Id(4).Update(user)
  }
  //6.2 SQL方式略,和insert类似
 //7.事务
  //7.1简单事务
  if false {
   session :=db.NewSession()
   defer session.Close()
   session.Begin()
   //业务:新添加学生，并且创建新的班级，如果班级因为主键冲突创建失败，则整个事务回滚
   _,err =session.SQL("insert into public.user(name,class_id) values('ft13',2)").Execute()
   //表中已经有id=3的班级了
   _,err =session.SQL("insert into public.class(id,name) values(3,'高中3班')").Execute()
   if err!=nil {
    session.Rollback()
   }
   session.Commit()
  }
  //7.2嵌套事务
  if false {
   session := db.NewSession()
   defer session.Close()
   session.Begin()
   _,err=session.Exec("insert into public.user(name,class_id) values('ft23',2)")
   if err!=nil {
    session.Rollback()
   }
   _,err=session.Exec("insert into public.user(id,name,class_id) values(1,'ft24',2)")
   if err!=nil {
    session.Rollback()
   }
   tx,_:=session.BeginTrans()
   _,err=tx.Session().Exec("insert into public.user(name,class_id) values('ft25',2)")
   if err!=nil {
    tx.RollbackTrans()
   }
   tx.CommitTrans()
   session.Commit()
  }
 //8.缓存:使用Raw方式修改以后，需要清理缓存
 if true {
   //建立500条数据
   session := db.NewSession()
   defer session.Close()
   if false {
    session.Begin()
    for i := 30; i  530; i++ {
     value := "ft" + strconv.Itoa(i)
     _, err = session.Exec("insert into public.user(name) values(?)", value)
     if err != nil {
      session.Rollback()
     }
    }
    session.Commit()
   }
   //查询前531条数据，并随意输出其中一条
   users := make([]User,10)
   db.SQL("select * from public.user where id531 order by id").Find(users)
   fmt.Println("读第一遍:","id:",users[50].Id,"name:",users[50].Name)
   db.SQL("select * from public.user where id531 order by id").Find(users)
   fmt.Println("读第二遍:","id:",users[50].Id,"name:",users[50].Name)
   var step int =1
   stepString := users[50].Name + strconv.Itoa(step)
   session.Exec("update public.user set name=? where id =45",stepString)
   //清理缓存
   db.ClearCache(new(User))
   time.Sleep(5*time.Second)
   session.SQL("select * from public.user where id531 order by id").Find(users)
   fmt.Println("读第三遍:","id:",users[50].Id,"name:",users[50].Name)
   //虽然很不好意思，但是就算开启了缓存数据也是脏了
 }
 //9.读写分离
 if false {
 //假设有多台服务器用来响应客户的读请求
 var dbGroup *xorm.EngineGroup
 conns :=[]string {
  "postgres://postgres:123@localhost:5432/test?sslmode=disable",
  "postgres://postgres:123@localhost:5432/test?sslmode=disable",
  "postgres://postgres:123@localhost:5432/test?sslmode=disable",
  "postgres://postgres:123@localhost:5432/test?sslmode=disable",
 }
 //负载均衡策略:(特性自行百度)
  // 1.xorm.RandomPolicy()随机访问负载均衡,
  // 2.xorm.WeightRandomPolicy([]int{2, 3,4})权重随机负载均衡
  // 3.xorm.RoundRobinPolicy() 轮询访问负载均衡
  // 4.xorm.WeightRoundRobinPolicy([]int{2, 3,4}) 权重轮训负载均衡
  // 5.xorm.LeastConnPolicy()最小连接数负载均衡
 dbGroup, err = xorm.NewEngineGroup("postgres", conns, xorm.RoundRobinPolicy())
 //dbGroup使用方法和db一致
   //简单查询
   dbGroup.SQL("inser into public.users(name) values('ft2000')").Execute()
   dbGroup.Exec("inser into public.users(name) values('ft2001')")
   //事务查询
   session :=dbGroup.NewSession()
   defer session.Close()
   session.Begin()
   _,err = session.Exec("inser into public.users(name) values('ft2001')")
   if err!=nil {
   session.Rollback()
   }
   session.Commit()
 }
}
//注意:
//1.postgresql好像不会默认按id增长排序，所以书写sql语句要提前写好order by id ，楼主没怎么写，咳咳
//2. [5.4] postgresql建表会建在public策略的table里，所以查询语句表明写的是public.xxxx,这也造成了连表orm查询会发生前缀报错,比如变成了"SELECT * FROM "public"."user" INNER JOIN "class" ON user.class_id=class.id 这和内部的split有关，
//3.[8.]带的缓存好像很容易失效,在创建500个数据后，经过查查改查的操作，查询到的结果是一样的始终是一样的，本来改值之后应该最后一遍查会变化，然而并没有,缓存功能即使清理了缓存，还是会读到脏的

int  integer
time.Time timestamp
int8 smallint
float64 numeric(8,3) (只要是numeric统统使用float64)
string text
string varchar