本文使用 Golang 对 sqlite3 数据库进行操作。
概述
Golang 操作数据库有统一的接口，当然也有xorm这样的库，笔者接触的项目不大，对sql自由组装有要求，同时也会将这些sql用于数据库客户端查询，因此偏向于使用原生的sql。
为方便起见，本文只针对sqlite进行连接、读写、事务的测试。理论上可以扩展到其它数据库的操作。
技术小结
- 引入的包有
"database/sql"、_ "github.com/mattn/go-sqlite3"。 - 使用
sql.Open打开数据库，对于sqlite3，不存在目标文件时，会自创并使用。 - 事务相关接口有：开始
SQLDB.Begin()、提交tx.Commit()、回滚tx.Rollback()、结束SQLDB.Close()。
设计
为让测试代码接近业务逻辑，设计场景如下：
- 设2个数据表：一为版本号表，一为信息明细表。
- 版本号更新了（如通过http下载数据，数据中有版本号），才更新明细表。程序通过读取数据库表的版本号进行判断。
- 允许上述数据表为空或不存在，由于sqlite3是基于文件的，也允许sqlite文件不存在。
- 同时写上述2个数据表，同时成功了方认为成功，因此使用到事务机制。
源码分析
完整代码见文后，本节按实现功能列出要点。
连接数据库
func CreateSqlite3(dbname string, create bool) (sqldb *sql.DB, err error) {
if create == false && !IsExist(dbname) {
return nil, errors.New("open database failed: " + dbname + " not found")
}
sqldb, err = sql.Open("sqlite3", dbname)
if err != nil {
return nil, errors.New("open database failed: " + err.Error())
}
err = sqldb.Ping()
if err != nil {
return nil, errors.New("connect database failed: " + err.Error())
}
fmt.Println("connect to ", dbname, "ok")
return
}
读取版本号
读取版本号，如果不存在，则创建对应的表。
func readOrCreateDBTable(sqldb *sql.DB) (version, updateTime string) {
needCreate := false
sqlstr := fmt.Sprintf(`select version, updateTime from %v order by version desc limit 1`,
tableVersion)
fmt.Printf("run sql: [%v]\n", sqlstr)
results, err := sqldb.Query(sqlstr)
if err != nil {
if strings.Contains(err.Error(), "no such table") {
needCreate = true
} else {
fmt.Println("query error: ", err)
return
}
}
if !needCreate {
for results.Next() {
var item1, item2 sql.NullString
err := results.Scan(&item1, &item2)
if err != nil {
fmt.Println("scan error: ", err)
break
}
if !item1.Valid || !item2.Valid {
continue
}
version = item1.String
updateTime = item2.String
}
defer results.Close()
} else {
fmt.Println("not found table, will create it.")
for _, item := range sqlarr {
_, err := sqldb.Exec(item)
if err != nil {
fmt.Printf("Exec sql failed: [%v] [%v] \n", err, item)
}
}
}
return
}
以事务方式入库
// 入库2个表，以事务方式
func insertDBBatch(gxList []InfoList_t, version string) (err error) {
SQLDB, err := CreateSqlite3(dbServer, false)
if err != nil {
// fmt.Println(err.Error())
return err
}
var tx *sql.Tx
tx, err = SQLDB.Begin()
if err != nil {
err = errors.New("begin sql error: " + err.Error())
return err
}
defer func() {
if err != nil {
err = errors.New("exec sql failed rollback: " + err.Error())
tx.Rollback()
} else {
err = nil
tx.Commit()
}
// 延时一会，关闭
Sleep(1000)
SQLDB.Close()
}()
err = insertDBVersion(tx, version)
if err != nil {
return
}
err = insertDBDetail(tx, gxList, version)
if err != nil {
return
}
return
}
函数开始时，先调用SQLDB.Begin()开始事务，分别调用insertDBVersion和insertDBDetail入库，只有2者同时成功，才调用tx.Commit()提交事务，否则调用tx.Rollback()回滚。提交事务或回滚，通过Golang的defer机制实现，逻辑较清晰。
测试
测试日志如下：
go test -v -run TestSqlite 没有数据库文件 test of sqlte3... connect to foobar.db3 ok run sql: select version, updateTime from myVersion order by version desc limit 1 not found table, will create it. got db version [] update time [] connect to foobar.db3 ok insert db version [] at: [2023-12-02 10:42:18] insert result: <nil> --- PASS: TestSqlite (1.04s) PASS 已有数据但版本较新 test of sqlte3... connect to foobar.db3 ok run sql: [select version, updateTime from myVersion order by version desc limit 1] got db version [20231202] update time [2023-12-02T10:48:20Z] connect to foobar.db3 ok insert db version [20231203] at: [2023-12-02 10:48:47] insert result: <nil> --- PASS: TestSqlite (1.03s) PASS
附
完整代码
package test
import (
"database/sql"
"errors"
"fmt"
"os"
"strings"
"testing"
"time"
"webdemo/pkg/com"
_ "github.com/mattn/go-sqlite3"
)
var (
// 数据库文件名及表名
dbServer string = "foobar.db3"
tableVersion string = "myVersion"
tableList string = "myList"
)
// 信息表 结构体可对于json风格数据传输解析
type InfoList_t struct {
Id int `json:"-"`
Version string `json:"-"`
Name string `json:"-"`
City string `json:"-"`
UpdateTime string `json:"-"`
}
var sqlarr []string = []string{
// 版本号
`CREATE TABLE "myVersion" (
"version" VARCHAR(20) NOT NULL,
"updateTime" datetime DEFAULT "",
PRIMARY KEY ("version")
);`,
// 信息表
`CREATE TABLE "myList" (
"id" int NOT NULL,
"version" VARCHAR(20) NOT NULL,
"name" VARCHAR(20) NOT NULL,
"city" VARCHAR(20) NOT NULL,
"updateTime" datetime DEFAULT "",
PRIMARY KEY ("id")
);`,
}
func IsExist(path string) bool {
_, err := os.Stat(path)
return err == nil || os.IsExist(err)
}
func Sleep(ms int) {
time.Sleep(time.Duration(ms) * time.Millisecond)
}
func CreateSqlite3(dbname string, create bool) (sqldb *sql.DB, err error) {
if create == false && !IsExist(dbname) {
return nil, errors.New("open database failed: " + dbname + " not found")
}
sqldb, err = sql.Open("sqlite3", dbname)
if err != nil {
return nil, errors.New("open database failed: " + err.Error())
}
err = sqldb.Ping()
if err != nil {
return nil, errors.New("connect database failed: " + err.Error())
}
fmt.Println("connect to ", dbname, "ok")
return
}
func readOrCreateDBTable(sqldb *sql.DB) (version, updateTime string) {
needCreate := false
sqlstr := fmt.Sprintf(`select version, updateTime from %v order by version desc limit 1`,
tableVersion)
fmt.Printf("run sql: [%v]\n", sqlstr)
results, err := sqldb.Query(sqlstr)
if err != nil {
if strings.Contains(err.Error(), "no such table") {
needCreate = true
} else {
fmt.Println("query error: ", err)
return
}
}
if !needCreate {
for results.Next() {
var item1, item2 sql.NullString
err := results.Scan(&item1, &item2)
if err != nil {
fmt.Println("scan error: ", err)
break
}
if !item1.Valid || !item2.Valid {
continue
}
version = item1.String
updateTime = item2.String
}
defer results.Close()
} else {
fmt.Println("not found table, will create it.")
for _, item := range sqlarr {
_, err := sqldb.Exec(item)
if err != nil {
fmt.Printf("Exec sql failed: [%v] [%v] \n", err, item)
}
}
}
return
}
func insertDBDetail(tx *sql.Tx, gxList []InfoList_t, version string) (err error) {
tablename := tableList
sqlstr := fmt.Sprintf(`DELETE FROM %v`, tablename)
stmt, err := tx.Prepare(sqlstr)
if err != nil {
err = errors.New("prepare for [" + sqlstr + "] failed: " + err.Error())
return
}
_, err = stmt.Exec()
if err != nil {
err = errors.New("delete " + tablename + "failed: " + err.Error())
return
}
sqlstr = fmt.Sprintf(`INSERT OR REPLACE INTO %v
(id, version, name, city, updateTime)
VALUES (?, ?, ?, ?, ?)`,
tablename)
stmt, _ = tx.Prepare(sqlstr)
for _, item := range gxList {
// item.Id = idx
item.Version = version
item.UpdateTime = com.GetNowDateTime("YYYY-MM-DD HH:mm:ss")
_, err = stmt.Exec(item.Id, item.Version, item.Name, item.City, item.UpdateTime)
if err != nil {
err = errors.New("insert " + tablename + "failed: " + err.Error())
return
}
}
return
// debug 制作bug
// TODO 制作锁住，制作语法错误
err = errors.New("database is locked")
return
}
func insertDBVersion(tx *sql.Tx, version string) (err error) {
tablename := tableVersion
sqlstr := fmt.Sprintf(`DELETE FROM %v`, tablename)
stmt, err := tx.Prepare(sqlstr)
if err != nil {
err = errors.New("prepare for [" + sqlstr + "] failed: " + err.Error())
return
}
_, err = stmt.Exec()
if err != nil {
err = errors.New("delete " + tablename + " failed: " + err.Error())
return
}
sqlstr = fmt.Sprintf(`INSERT OR REPLACE INTO %v (version, updateTime) VALUES (?, ?)`, tablename)
stmt, err = tx.Prepare(sqlstr)
if err != nil {
err = errors.New("prepare for [" + sqlstr + "] failed: " + err.Error())
return
}
updateTime := com.GetNowDateTime("YYYY-MM-DD HH:mm:ss")
fmt.Printf("insert db version [%v] at: [%v]\n", version, updateTime)
_, err = stmt.Exec(version, updateTime)
if err != nil {
err = errors.New("insert " + tablename + "failed: " + err.Error())
return
}
return
}
// 入库2个表，以事务方式
func insertDBBatch(gxList []InfoList_t, version string) (err error) {
SQLDB, err := CreateSqlite3(dbServer, false)
if err != nil {
// fmt.Println(err.Error())
return err
}
var tx *sql.Tx
tx, err = SQLDB.Begin()
if err != nil {
err = errors.New("begin sql error: " + err.Error())
return err
}
defer func() {
if err != nil {
err = errors.New("exec sql failed rollback: " + err.Error())
tx.Rollback()
} else {
err = nil
tx.Commit()
}
// 延时一会，关闭
Sleep(1000)
SQLDB.Close()
}()
err = insertDBVersion(tx, version)
if err != nil {
return
}
err = insertDBDetail(tx, gxList, version)
if err != nil {
return
}
return
}
//
func makeData() (gxList []InfoList_t) {
var tmp InfoList_t
tmp.Id = 100
tmp.Version = "100"
tmp.Name = "latelee"
tmp.City = "梧州"
gxList = append(gxList, tmp)
tmp = InfoList_t{}
tmp.Id = 250
tmp.Version = "250"
tmp.Name = "latelee"
tmp.City = "岑溪"
gxList = append(gxList, tmp)
return
}
// 读取基础信息，尝试创建表
func readDBVersion() (version, datetime string) {
SQLDB, err := CreateSqlite3(dbServer, true)
if err != nil {
fmt.Println(err.Error())
return
}
version, datetime = readOrCreateDBTable(SQLDB)
SQLDB.Close()
return
}
func TestSqlite(t *testing.T) {
fmt.Println("test of sqlte3...")
// 1 尝试获取数据表的版本号（可能为空）
version, datetime := readDBVersion()
fmt.Printf("got db version [%v] update time [%v]\n", version, datetime)
// 2 模拟业务：自定义版本号，较新时，才入库
myVer := "20231202"
if myVer > version {
data := makeData()
err := insertDBBatch(data, myVer)
fmt.Println("insert result: ", err)
} else {
fmt.Println("db is newest, do nothing")
}
}
