Refactor dialect.go so its easier to add new dialects

dialect.go

@@ -2,13 +2,32 @@ package ksql
 
 import "strconv"
 
+type insertMethod int
+
+const (
+	insertWithReturning insertMethod = iota
+	insertWithLastInsertID
+	insertWithNoIDRetrieval
+)
+
+var supportedDialects = map[string]dialect{
+	"postgres": &postgresDialect{},
+	"sqlite3":  &sqlite3Dialect{},
+	// "mysql":    &mysqlDialect{},
+}
+
 type dialect interface {
+	InsertMethod() insertMethod
 	Escape(str string) string
 	Placeholder(idx int) string
 }
 
 type postgresDialect struct{}
 
+func (postgresDialect) InsertMethod() insertMethod {
+	return insertWithReturning
+}
+
 func (postgresDialect) Escape(str string) string {
 	return `"` + str + `"`
 }
@@ -19,6 +38,10 @@ func (postgresDialect) Placeholder(idx int) string {
 
 type sqlite3Dialect struct{}
 
+func (sqlite3Dialect) InsertMethod() insertMethod {
+	return insertWithLastInsertID
+}
+
 func (sqlite3Dialect) Escape(str string) string {
 	return "`" + str + "`"
 }
@@ -27,9 +50,16 @@ func (sqlite3Dialect) Placeholder(idx int) string {
 	return "?"
 }
 
-func getDriverDialect(driver string) dialect {
-	return map[string]dialect{
-		"postgres": &postgresDialect{},
-		"sqlite3":  &sqlite3Dialect{},
-	}[driver]
+type mysqlDialect struct{}
+
+func (mysqlDialect) InsertMethod() insertMethod {
+	return insertWithLastInsertID
+}
+
+func (mysqlDialect) Escape(str string) string {
+	return "`" + str + "`"
+}
+
+func (mysqlDialect) Placeholder(idx int) string {
+	return "?"
 }

docker-compose.yml

@@ -15,3 +15,11 @@ services:
     environment:
       - POSTGRES_USER=postgres
       - POSTGRES_PASSWORD=postgres
+
+  mysql:
+    image: mysql
+    restart: always
+    ports:
+      - "127.0.0.1:3306:3306"
+    environment:
+      MYSQL_ROOT_PASSWORD: mysql

ksql.go

@@ -32,14 +32,6 @@ type sqlProvider interface {
 	QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error)
 }
 
-type insertMethod int
-
-const (
-	insertWithReturning insertMethod = iota
-	insertWithLastInsertID
-	insertWithNoIDRetrieval
-)
-
 // Config describes the optional arguments accepted
 // by the ksql.New() function.
 type Config struct {
@@ -75,7 +67,7 @@ func New(
 
 	db.SetMaxOpenConns(config.MaxOpenConns)
 
-	dialect := getDriverDialect(dbDriver)
+	dialect := supportedDialects[dbDriver]
 	if dialect == nil {
 		return DB{}, fmt.Errorf("unsupported driver `%s`", dbDriver)
 	}
@@ -84,18 +76,10 @@ func New(
 		config.IDColumns = []string{"id"}
 	}
 
-	var insertMethod insertMethod
-	switch dbDriver {
-	case "sqlite3":
-		insertMethod = insertWithLastInsertID
-		if len(config.IDColumns) > 1 {
+	insertMethod := dialect.InsertMethod()
+	if len(config.IDColumns) > 1 && insertMethod == insertWithLastInsertID {
 		insertMethod = insertWithNoIDRetrieval
 	}
-	case "postgres":
-		insertMethod = insertWithReturning
-	default:
-		return DB{}, fmt.Errorf("unsupported driver `%s`", dbDriver)
-	}
 
 	return DB{
 		dialect:   dialect,

ksql_test.go

@@ -33,7 +33,7 @@ type Address struct {
 }
 
 func TestQuery(t *testing.T) {
-	for _, driver := range []string{"sqlite3", "postgres"} {
+	for driver := range supportedDialects {
 		t.Run(driver, func(t *testing.T) {
 			t.Run("using slice of structs", func(t *testing.T) {
 				err := createTable(driver)
@@ -222,7 +222,7 @@ func TestQuery(t *testing.T) {
 }
 
 func TestQueryOne(t *testing.T) {
-	for _, driver := range []string{"sqlite3", "postgres"} {
+	for driver := range supportedDialects {
 		t.Run(driver, func(t *testing.T) {
 			err := createTable(driver)
 			if err != nil {
@@ -318,7 +318,7 @@ func TestQueryOne(t *testing.T) {
 }
 
 func TestInsert(t *testing.T) {
-	for _, driver := range []string{"sqlite3", "postgres"} {
+	for driver := range supportedDialects {
 		t.Run(driver, func(t *testing.T) {
 			t.Run("using slice of structs", func(t *testing.T) {
 				err := createTable(driver)
@@ -446,7 +446,7 @@ func TestInsert(t *testing.T) {
 }
 
 func TestDelete(t *testing.T) {
-	for _, driver := range []string{"sqlite3", "postgres"} {
+	for driver := range supportedDialects {
 		t.Run(driver, func(t *testing.T) {
 			err := createTable(driver)
 			if err != nil {
@@ -589,7 +589,7 @@ func TestDelete(t *testing.T) {
 }
 
 func TestUpdate(t *testing.T) {
-	for _, driver := range []string{"sqlite3", "postgres"} {
+	for driver := range supportedDialects {
 		t.Run(driver, func(t *testing.T) {
 			err := createTable(driver)
 			if err != nil {
@@ -758,7 +758,7 @@ func TestUpdate(t *testing.T) {
 }
 
 func TestQueryChunks(t *testing.T) {
-	for _, driver := range []string{"sqlite3", "postgres"} {
+	for driver := range supportedDialects {
 		t.Run(driver, func(t *testing.T) {
 			t.Run("should query a single row correctly", func(t *testing.T) {
 				err := createTable(driver)
@@ -1156,7 +1156,7 @@ func TestQueryChunks(t *testing.T) {
 }
 
 func TestTransaction(t *testing.T) {
-	for _, driver := range []string{"sqlite3", "postgres"} {
+	for driver := range supportedDialects {
 		t.Run(driver, func(t *testing.T) {
 			t.Run("should query a single row correctly", func(t *testing.T) {
 				err := createTable(driver)
@@ -1391,7 +1391,7 @@ func newTestDB(db *sql.DB, driver string, tableName string, ids ...string) DB {
 
 	return DB{
 		driver:    driver,
-		dialect:   getDriverDialect(driver),
+		dialect:   supportedDialects[driver],
 		db:        db,
 		tableName: tableName,