英文:
Initialize database as global variable
问题
将数据库初始化为全局变量是一个好主意吗？它能够工作吗？
我在考虑以下的代码：
func MustDB(d *sql.DB, err error) *sql.DB {
if err != nil {
log.Panic(err)
}
return d
}
// 我不知道的是如何调用db.Close()
// 用户名和密码也可以类似的方式读取
var db *DB = MustDB(db.Open(...))
func MustPrepare(db *sql.DB, query string) *sql.Stmt {
res, err := sql.Prepare(db, query)
if err!=nil {
log.Panic(err)
}
return ret;
}
优点是，我可以将预编译的 SQL 语句作为全局变量简单地创建。我不需要创建和管理一个存储，将所有的 SQL 命令放在其中。我只需要编写：
var s1 *sql.Stmt = MustPrepare(db, "SELECT * FROM MyTable")
var s2 *sql.Stmt = MustPrepare(db, "INSERT INTO MyTable(col1, col2) VALUES(?,?)")
var s3 *sql.Stmt = MustPrepare(db, "DELETE FROM MyTable WHERE col1=?")
你认为这种模式有用，还是根本无法工作？
英文:
Is it a good idea to initialize databaze as global variable? Can it work?
I'm thinking about something like that:
func MustDB(d *sql.DB, err error) *sql.DB {
if err != nil {
log.Panic(err)
}
return d
}
// what I don't know - is how to call db.Close()
// username and password can also be read similar way
var db *DB = MustDB(db.Open(...))
func MustPrepare(db *sql.DB, query string) *sql.Stmt {
res, err := sql.Prepare(db, query)
if err!=nil {
log.Panic(err)
}
return ret;
}
The advantage is, I can simple create prepared sql statements as global variables. I don't have to create and manage a storage, where all sql commands will be put. Only I write:
var s1 *sql.Stmt = MustPrepare(db, "SELECT * FROM MyTable")
var s2 *sql.Stmt = MustPrepare(db, "INSERT INTO MyTable(col1, col2) VALUES(?,?)")
var s3 *sql.Stmt = MustPrepare(db, "DELETE FROM MyTable WHERE col1=?")
Do you think, that pattern is usefull, or it cannot work at all.
答案1
得分: 3
在Go语言中，通常使用Open函数（至少在数据库访问包中是全局的）来初始化一个全局的*DB结构体。这并不会打开一个实际的数据库连接，而是创建一个连接池。因此，应该只有一个实例。你可以在包的init函数中进行初始化。
参考以下链接获取一个很好的入门指南：
http://go-database-sql.org/
或者
https://www.vividcortex.com/blog/2015/01/14/the-ultimate-guide-to-building-database-driven-apps-with-go/
英文:
In go you typicallly initialize a global *DB struct using Open (at least global in your Database Access package). That does not open an actual connection to the DB, but creates a connection pool. Therefore there should be only one instance of it. You can initialize that in init of your package.
See
http://go-database-sql.org/
or
https://www.vividcortex.com/blog/2015/01/14/the-ultimate-guide-to-building-database-driven-apps-with-go/
for a good introductory guide.
答案2
得分: 0
是的，这是一个很好的方法。当你阅读Go文档时，它明确告诉你：
关闭DB是很少见的，因为DB句柄应该是长期存在的，并在许多Go协程之间共享。
Go会维护自己的空闲连接池。因此，应该只调用一次Open函数。很少需要关闭DB。
英文:
Yes it is a good approach. when you go through the go documentation it clearly tells you
> It is rare to Close a DB, as the DB handle is meant to be long-lived
> and shared between many go routines.
Go maintains its own pool of idle connections. Thus, the Open function should be called just once. It is rarely necessary to close a DB.
答案3
得分: -2
作为一个经验法则，我认为这种使用数据库连接的方式并不是一个好的实践，你应该将其私有化，并在需要时打开/关闭它 
但是如果它能够正常工作并且你喜欢这种方式，那么就没有什么问题。
英文:
As a rule of thumb I don't think its good practice to use database connections this way, you should privatize it and just open/close as you need it
But if it works and you like it then nothings wrong with doing it that way.
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