Use fs.FS

go.mod

@@ -0,0 +1,3 @@
+module git.fuyu.moe/Fuyu/migrate/v2
+
+go 1.16

migrate.go

@@ -5,14 +5,14 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
+	"io/fs"
 	"strconv"
 )
 
 // Options contains all settings
 type Options struct {
-	TableName   string // Name used for version info table; defaults to DefaultTableName if not set
-	Schema      string // Schema used for version info table; For PostgreSQL, ignored if not set
-	AssetPrefix string
+	TableName string // Name used for version info table; defaults to DefaultTableName if not set
+	Schema    string // Schema used for version info table; In PostgreSQL the current schema is changed to the one specified here
 }
 
 // DefaultTableName is the name used when no TableName is specified in Options
@@ -21,34 +21,20 @@ const DefaultTableName = `version`
 // ErrUpdatesMissing indicates an update is missing, making it impossible to execute the migration
 var ErrUpdatesMissing = errors.New(`Missing migration files`)
 
-// ErrDatabaseNewer indicates that the database version is newer than the requested version. We throw an error because downgrades might cause dataloss
-var ErrDatabaseNewer = errors.New(`Current version is newer than the requested version`)
-
 const fileFormat = `%04d.sql`
 
 // AssetFunc is a function that returns the data for the given name
 type AssetFunc func(string) ([]byte, error)
 
-// Migrate executes migrations to get to the desired version
+// Migrate executes all migrations
+// Filenames need to have incrementing numbers
 // Downgrading is not supported as it could result in data loss
-func Migrate(db *sql.DB, version int, o Options, asset AssetFunc) error {
-	if o.TableName == `` {
-		o.TableName = DefaultTableName
-	}
-
-	var err error
-
-	searchPath := `public`
-	_ = db.QueryRow(`SHOW search_path`).Scan(&searchPath)
-
-	if o.Schema != `` {
-		_, _ = db.Exec(`CREATE SCHEMA IF NOT EXISTS ` + o.Schema)
-
-		_, err = db.Exec(`SET search_path TO ` + o.Schema)
-		if err != nil {
-			return err
-		}
+func Migrate(db *sql.DB, o Options, assets fs.FS) error {
+	entries, err := fs.ReadDir(assets, `.`)
+	if err != nil {
+		panic(`failed to read list of files`)
 	}
+	version := len(entries)
 
 	tx, err := db.Begin()
 	if err != nil {
@@ -56,12 +42,34 @@ func Migrate(db *sql.DB, version int, o Options, asset AssetFunc) error {
 	}
 	defer tx.Rollback()
 
-	_, err = tx.Exec(`CREATE TABLE IF NOT EXISTS ` + o.TableName + ` (Version integer NOT NULL PRIMARY KEY)`)
+	dbType := getDbType(db)
+	searchPath := `public`
+	if o.TableName == `` {
+		o.TableName = DefaultTableName
+	}
+
+	if o.Schema != `` {
+		err = createSchemaIfNotExists(tx, o.Schema)
+		if err != nil {
+			return err
+		}
+
+		if dbType == `pq` {
+			_ = tx.QueryRow(`SHOW search_path`).Scan(&searchPath)
+
+			_, err = tx.Exec(`SET search_path TO ` + o.Schema)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	versionTable, err := createTableIfNotExists(tx, o.Schema, o.TableName)
 	if err != nil {
 		return err
 	}
 
-	row := tx.QueryRow(`SELECT Version FROM ` + o.TableName + ` ORDER BY Version DESC`)
+	row := tx.QueryRow(`SELECT version FROM ` + versionTable + ` ORDER BY Version DESC`)
 
 	var v int
 	err = row.Scan(&v)
@@ -69,28 +77,27 @@ func Migrate(db *sql.DB, version int, o Options, asset AssetFunc) error {
 		return err
 	}
 
-	if v > version {
-		return ErrDatabaseNewer
-	}
-
 	for i := v + 1; i <= version; i++ {
-		script, err := asset(fmt.Sprintf(o.AssetPrefix+fileFormat, i))
+		fileName := fmt.Sprintf(fileFormat, i)
+		errorf := func(e error) error { return fmt.Errorf(`migration "%s" failed: %w`, fileName, e) }
+
+		script, err := fs.ReadFile(assets, fileName)
 		if err != nil {
-			return ErrUpdatesMissing
+			return errorf(ErrUpdatesMissing)
 		}
 
 		_, err = tx.Exec(string(script))
 		if err != nil {
-			return err
+			return errorf(err)
 		}
 
-		_, err = tx.Exec(`INSERT INTO ` + o.TableName + ` VALUES (` + strconv.Itoa(i) + `)`)
+		_, err = tx.Exec(`INSERT INTO ` + versionTable + ` (version) VALUES (` + strconv.Itoa(i) + `)`)
 		if err != nil {
-			return err
+			return errorf(err)
 		}
 	}
 
-	if o.Schema != `` {
+	if dbType == `pq` && o.Schema != `` {
 		_, err = tx.Exec(`SET search_path TO ` + searchPath)
 		if err != nil {
 			return err

query.go

@@ -0,0 +1,35 @@
+package migrate
+
+import "database/sql"
+
+func createSchemaIfNotExists(tx *sql.Tx, schema string) error {
+	row := tx.QueryRow(`SELECT 1 FROM information_schema.schemata WHERE schema_name = '` + schema + `'`)
+	err := row.Scan(new(int))
+	if err == sql.ErrNoRows {
+		_, err = tx.Exec(`CREATE SCHEMA ` + schema)
+		if err != nil {
+			return err
+		}
+	}
+	return err
+}
+
+func createTableIfNotExists(tx *sql.Tx, schema, table string) (string, error) {
+	versionTable := table
+	var schemaCond string
+
+	if schema != `` {
+		versionTable = schema + `.` + table
+		schemaCond = ` AND table_schema = '` + schema + `'`
+	}
+
+	row := tx.QueryRow(`SELECT 1 FROM information_schema.tables WHERE table_name = '` + table + `'` + schemaCond)
+	err := row.Scan(new(int))
+	if err == sql.ErrNoRows {
+		_, err = tx.Exec(`CREATE TABLE ` + versionTable + ` (version integer NOT NULL PRIMARY KEY)`)
+		if err != nil {
+			return ``, err
+		}
+	}
+	return versionTable, err
+}

util.go

@@ -0,0 +1,29 @@
+package migrate
+
+import (
+	"database/sql"
+	"reflect"
+	"strings"
+)
+
+func getPkgName(db *sql.DB) string {
+	t := reflect.TypeOf(db.Driver())
+	if t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	path := t.PkgPath()
+	parts := strings.Split(path, `/vendor/`)
+	return parts[len(parts)-1]
+}
+
+func getDbType(db *sql.DB) string {
+	switch getPkgName(db) {
+	case `github.com/lib/pq`, `github.com/jackc/pgx/stdlib`:
+		return `pq`
+	case `github.com/go-sql-driver/mysql`, `github.com/ziutek/mymysql/godrv`:
+		return `my`
+	case `github.com/denisenkom/go-mssqldb`:
+		return `ms`
+	}
+	return ``
+}