Concurrent transactions.

driver/driver.go

@@ -119,10 +119,8 @@ func (d *SQLite) newConnector(name string) (*connector, error) {
 	}
 
 	switch txlock {
-	case "":
-		c.txBegin = "BEGIN"
-	case "deferred", "immediate", "exclusive":
-		c.txBegin = "BEGIN " + txlock
+	case "", "deferred", "concurrent", "immediate", "exclusive":
+		c.txLock = txlock
 	default:
 		return nil, fmt.Errorf("sqlite3: invalid _txlock: %s", txlock)
 	}
@@ -147,7 +145,7 @@ func (d *SQLite) newConnector(name string) (*connector, error) {
 type connector struct {
 	driver  *SQLite
 	name    string
-	txBegin string
+	txLock  string
 	tmRead  sqlite3.TimeFormat
 	tmWrite sqlite3.TimeFormat
 	pragmas bool
@@ -159,7 +157,7 @@ func (n *connector) Driver() driver.Driver {
 
 func (n *connector) Connect(ctx context.Context) (_ driver.Conn, err error) {
 	c := &conn{
-		txBegin: n.txBegin,
+		txLock:  n.txLock,
 		tmRead:  n.tmRead,
 		tmWrite: n.tmWrite,
 	}
@@ -209,12 +207,11 @@ func (n *connector) Connect(ctx context.Context) (_ driver.Conn, err error) {
 
 type conn struct {
 	*sqlite3.Conn
-	txBegin    string
-	txCommit   string
-	txRollback string
-	tmRead     sqlite3.TimeFormat
-	tmWrite    sqlite3.TimeFormat
-	readOnly   byte
+	txLock   string
+	txReset  string
+	tmRead   sqlite3.TimeFormat
+	tmWrite  sqlite3.TimeFormat
+	readOnly byte
 }
 
 var (
@@ -236,27 +233,25 @@ func (c *conn) Begin() (driver.Tx, error) {
 }
 
 func (c *conn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, error) {
-	txBegin := c.txBegin
-	c.txCommit = `COMMIT`
-	c.txRollback = `ROLLBACK`
-
-	if opts.ReadOnly {
-		txBegin = `
-			BEGIN deferred;
-			PRAGMA query_only=on`
-		c.txRollback = `
-			ROLLBACK;
-			PRAGMA query_only=` + string(c.readOnly)
-		c.txCommit = c.txRollback
-	}
-
+	var txLock string
 	switch opts.Isolation {
 	default:
 		return nil, util.IsolationErr
-	case
-		driver.IsolationLevel(sql.LevelDefault),
-		driver.IsolationLevel(sql.LevelSerializable):
-		break
+	case driver.IsolationLevel(sql.LevelLinearizable):
+		txLock = "exclusive"
+	case driver.IsolationLevel(sql.LevelSerializable):
+		txLock = "immediate"
+	case driver.IsolationLevel(sql.LevelDefault):
+		if !opts.ReadOnly {
+			txLock = c.txLock
+		}
+	}
+
+	c.txReset = ``
+	txBegin := `BEGIN ` + txLock
+	if opts.ReadOnly {
+		txBegin += ` ; PRAGMA query_only=on`
+		c.txReset = `; PRAGMA query_only=` + string(c.readOnly)
 	}
 
 	old := c.Conn.SetInterrupt(ctx)
@@ -270,7 +265,7 @@ func (c *conn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver.Tx, e
 }
 
 func (c *conn) Commit() error {
-	err := c.Conn.Exec(c.txCommit)
+	err := c.Conn.Exec(`COMMIT` + c.txReset)
 	if err != nil && !c.Conn.GetAutocommit() {
 		c.Rollback()
 	}
@@ -278,11 +273,11 @@ func (c *conn) Commit() error {
 }
 
 func (c *conn) Rollback() error {
-	err := c.Conn.Exec(c.txRollback)
+	err := c.Conn.Exec(`ROLLBACK` + c.txReset)
 	if errors.Is(err, sqlite3.INTERRUPT) {
 		old := c.Conn.SetInterrupt(context.Background())
 		defer c.Conn.SetInterrupt(old)
-		err = c.Conn.Exec(c.txRollback)
+		err = c.Conn.Exec(`ROLLBACK` + c.txReset)
 	}
 	return err
 }

tests/txn_test.go

@@ -339,6 +339,21 @@ func TestConn_Transaction_rollback(t *testing.T) {
 	}
 }
 
+func TestConn_Transaction_concurrent(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	_, err = db.BeginConcurrent()
+	if !errors.Is(err, sqlite3.ERROR) {
+		t.Errorf("got %v, want sqlite3.ERROR", err)
+	}
+}
+
 func TestConn_Savepoint_exec(t *testing.T) {
 	t.Parallel()
 

txn.go

@@ -32,6 +32,19 @@ func (c *Conn) Begin() Txn {
 	return Txn{c}
 }
 
+// BeginConcurrent starts a concurrent transaction.
+//
+// Experimental: requires a custom build of SQLite.
+//
+// https://sqlite.org/cgi/src/doc/begin-concurrent/doc/begin_concurrent.md
+func (c *Conn) BeginConcurrent() (Txn, error) {
+	err := c.Exec(`BEGIN CONCURRENT`)
+	if err != nil {
+		return Txn{}, err
+	}
+	return Txn{c}, nil
+}
+
 // BeginImmediate starts an immediate transaction.
 //
 // https://sqlite.org/lang_transaction.html