golang使用CockroachDB

步骤1.安装Go pq驱动程序

go get -u github.com/lib/pq

步骤2.创建maxroach用户和bank数据库

启动内置的SQL客户端：

cockroach sql --certs-dir=certs

在SQL Shell中，发出以下语句来创建maxroach用户和bank数据库：

CREATE USER IF NOT EXISTS maxroach;CREATE DATABASE bank;

授予maxroach用户必要的权限：

GRANT ALL ON DATABASE bank TO maxroach;

退出SQL Shell：

\q

步骤3.为maxroach用户生成证书

maxroach通过运行以下命令为用户创建证书和密钥。代码示例将以该用户身份运行。

cockroach cert create-client maxroach --certs-dir=certs --ca-key=my-safe-directory/ca.key

步骤4.运行Go代码

现在已经有了一个数据库和一个用户，将运行代码来创建表并插入一些行，然后运行代码以作为原子事务读取和更新值。

基本陈述

首先，使用以下代码以maxroach用户身份连接并执行一些基本的SQL语句，创建表，插入行以及读取和打印行。

package mainimport ("database/sql"
"fmt"
"log"_ "github.com/lib/pq"
)func main() {db, err := sql.Open("postgres","postgresql://maxroach@localhost:26257/bank?ssl=true&sslmode=require&sslrootcert=certs/ca.crt&sslkey=certs/client.maxroach.key&sslcert=certs/client.maxroach.crt")if err != nil {log.Fatal("error connecting to the database: ", err)}defer db.Close()if _, err := db.Exec("CREATE TABLE IF NOT EXISTS accounts (id INT PRIMARY KEY, balance INT)"); err != nil {log.Fatal(err)}if _, err := db.Exec("INSERT INTO accounts (id, balance) VALUES (1, 1000), (2, 250)"); err != nil {log.Fatal(err)}rows, err := db.Query("SELECT id, balance FROM accounts")
if err != nil {log.Fatal(err)
}
defer rows.Close()
fmt.Println("Initial balances:")
for rows.Next() {var id, balance intif err := rows.Scan(&id, &balance); err != nil {log.Fatal(err)}fmt.Printf("%d %d\n", id, balance)
}

}

创建事务（带重试逻辑）

Go代码：

package mainimport ("context""database/sql""fmt""log""github.com/cockroachdb/cockroach-go/crdb"
)func transferFunds(tx *sql.Tx, from int, to int, amount int) error {var fromBalance intif err := tx.QueryRow("SELECT balance FROM accounts WHERE id = $1", from).Scan(&fromBalance); err != nil {return err}if fromBalance < amount {return fmt.Errorf("insufficient funds")}if _, err := tx.Exec("UPDATE accounts SET balance = balance - $1 WHERE id = $2", amount, from); err != nil {return err}if _, err := tx.Exec("UPDATE accounts SET balance = balance + $1 WHERE id = $2", amount, to); err != nil {return err}return nil
}func main() {//非安全模式db, err := sql.Open("postgres", "postgresql://maxroach@localhost:26257/bank?sslmode=disable")//安全模式//db, err := sql.Open("postgres", "postgresql://maxroach@localhost:26257/bank?ssl=true&sslmode=require&sslrootcert=certs/ca.crt&sslkey=certs/client.maxroach.key&sslcert=certs/client.maxroach.crt")if err != nil {log.Fatal("error connecting to the database: ", err)}// Run a transfer in a transaction.err = crdb.ExecuteTx(context.Background(), db, nil, func(tx *sql.Tx) error {return transferFunds(tx, 1 /* from acct# */, 2 /* to acct# */, 100 /* amount   */)})if err == nil {fmt.Println("Success")} else {log.Fatal("error: ", err)}
}

在默认的隔离级别SERIALIZABLE下，因读写冲突导致事务执行失败，需要用户主动地重新提交事务。用户也实现通用的retry函数在事务内部重新执行事务。

在Golang环境下，CockroachDB的retry函数位于CockroachDB Go客户端的crdb包中，用户需要将相关库克隆到$GOPATH当中：

mkdir -p $GOPATH/src/github.com/cockroachdb
cd $GOPATH/src/github.com/cockroachdb
git clone git@github.com:cockroachdb/cockroach-go.git

执行：

go run txn-sample.go

输出：

Success

执行查询：

cockroach sql --insecure -e 'SELECT id, balance FROM accounts' --database=bank
+----+---------+
| id | balance |
+----+---------+
|  1 |     900 |
|  2 |     350 |
+----+---------+
(2 rows)

使用GORM框架

步骤 1: 安装GORM

go get -u github.com/lib/pq # dependency
go get -u github.com/jinzhu/gorm

步骤 2: 启动节点

以非安全模式启动节点：

cockroach start --insecure --store=hello-1 --host=localhost

步骤 3: 创建用户

执行cockroach user命令创建maxroach用户：

cockroach user set maxroach --insecure

步骤 4: 创建数据库并授权

以root用户启动内置的SQL客户端，创建bank数据库并授权maxroach用户。

cockroach sql --insecure -e 'CREATE DATABASE bank'
cockroach sql --insecure -e 'GRANT ALL ON DATABASE bank TO maxroach'

步骤 5: 编写执行Go代码

下述Go代码中，代码db.AutoMigrate(&Account{}将根据Account模型创建accounts表：

package mainimport ("fmt""log""github.com/jinzhu/gorm"_ "github.com/jinzhu/gorm/dialects/postgres"
)type Account struct {ID      int `gorm:"primary_key"`Balance int
}func main() {//非安全模式const addr = "postgresql://maxroach@localhost:26257/bank?sslmode=disable"//安全模式//const addr = "postgresql://maxroach@localhost:26257/bank?ssl=true&sslmode=require&sslrootcert=certs/ca.crt&sslkey=certs/client.maxroach.key&sslcert=certs/client.maxroach.crt"db, err := gorm.Open("postgres", addr)if err != nil {log.Fatal(err)}defer db.Close()db.AutoMigrate(&Account{})db.Create(&Account{ID: 1, Balance: 1000})db.Create(&Account{ID: 2, Balance: 250})var accounts []Accountdb.Find(&accounts)fmt.Println("Initial balances:")for _, account := range accounts {fmt.Printf("%d %d\n", account.ID, account.Balance)}
}

执行：

go run gorm-basic-sample.go

输出：

Initial balances:
1 1000
2 250

执行查询：

cockroach sql --insecure -e 'SELECT id, balance FROM accounts' --database=bank
+----+---------+
| id | balance |
+----+---------+
|  1 |    1000 |
|  2 |     250 |
+----+---------+
(2 rows)