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package main
import (
"log"
"fmt"
"path/filepath"
"io"
"os"
"os/user"
"os/exec"
"strconv"
"database/sql"
_ "github.com/go-sql-driver/mysql"
)
const databaseSchemaVersion int = 2 // this defines the needed version for the
// executable
func setupDatabase() *sql.DB {
u,err := user.Current()
if err != nil {
log.Fatal(err)
}
target := fmt.Sprintf("%s@unix(%s)/%s", u.Username, config.Database.Socket,
config.Database.Database)
db,err := sql.Open("mysql", target)
if err != nil {
log.Fatal(err)
}
err = db.Ping()
if err != nil {
log.Fatal(err)
}
migrate(db)
log.Printf("Connected to database: %s\n", target)
return db
}
func migrate(db *sql.DB) {
const t = databaseSchemaVersion // targeted database schema version
for {
v := schemaVersion(db) // read schema version from DB table
// handle current database schema which is newer than targeted one
if v > t {
log.Fatalf(
"Current database schema version is %d but newest is %d!", v, t)
}
// break if targeted version is already reached
if v == t {
break
}
// execute migration
log.Printf("Starting database schema migration to version %d.\n", v+1)
path := filepath.Join(config.Database.Migrations,
fmt.Sprintf("%04d_migration.sql", v+1))
RunSqlScript(path)
log.Printf("Finished database schema migration to version %d.\n", v+1)
}
}
func RunSqlScript(path string) {
script, err := os.Open(path)
if err != nil {
log.Fatalf("Could not open SQL script '%s'!\n", path)
}
cmd := exec.Command("mariadb")
stdin, err := cmd.StdinPipe()
if err != nil {
log.Fatalf("Could not open stdin of mariadb process!\n%v", err)
}
err = cmd.Start()
if err != nil {
log.Fatalf("Could not start mariadb process!\n%v", err)
}
io.Copy(stdin, script)
stdin.Close()
err = cmd.Wait()
if err != nil {
log.Fatalf("Failed to wait for SQL script to finish!\n%v", err)
}
}
func schemaVersion(db *sql.DB) int {
// ask database for schema version
cmd := "SELECT value FROM meta WHERE (identifier='version');"
rows, err := db.Query(cmd)
// handle missing meta table
if err != nil {
log.Fatal(err)
}
// handle successful schema version query
defer rows.Close()
rows.Next()
var version string
err = rows.Scan(&version)
// handle missing version field in meta table
if err != nil {
log.Fatal(err)
}
// convert to integer and handle error
v, err := strconv.Atoi(version)
if err != nil {
log.Fatalf("Could not convert database schema version '%s' to int.\n",
version)
}
return v
}
func dbCleanup(db *sql.DB) {
err := db.Close()
if err != nil {
log.Println("Could not close database connection")
} else {
log.Println("Closed database connection")
}
}
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