Query pragmas at startup.

driver/driver.go

@@ -45,12 +45,12 @@ func init() {
 type sqlite struct{}
 
 func (sqlite) Open(name string) (_ driver.Conn, err error) {
-	c, err := sqlite3.Open(name)
+	var c conn
+	c.conn, err = sqlite3.Open(name)
 	if err != nil {
 		return nil, err
 	}
 
-	var txBegin string
 	var pragmas []string
 	if strings.HasPrefix(name, "file:") {
 		if _, after, ok := strings.Cut(name, "?"); ok {
@@ -58,9 +58,9 @@ func (sqlite) Open(name string) (_ driver.Conn, err error) {
 
 			switch s := query.Get("_txlock"); s {
 			case "":
-				txBegin = "BEGIN"
+				c.txBegin = "BEGIN"
 			case "deferred", "immediate", "exclusive":
-				txBegin = "BEGIN " + s
+				c.txBegin = "BEGIN " + s
 			default:
 				c.Close()
 				return nil, fmt.Errorf("sqlite3: invalid _txlock: %s", s)
@@ -70,20 +70,36 @@ func (sqlite) Open(name string) (_ driver.Conn, err error) {
 		}
 	}
 	if len(pragmas) == 0 {
-		err := c.Exec(`
-			PRAGMA busy_timeout=60000;
+		err := c.conn.Exec(`
 			PRAGMA locking_mode=normal;
+			PRAGMA busy_timeout=60000;
 		`)
 		if err != nil {
 			c.Close()
 			return nil, err
 		}
+		c.reusable = true
+	} else {
+		s, _, err := c.conn.Prepare(`
+			SELECT * FROM
+				PRAGMA_locking_mode,
+				PRAGMA_query_only;
+		`)
+		if err != nil {
+			c.Close()
+			return nil, err
+		}
+		if s.Step() {
+			c.reusable = s.ColumnText(0) == "normal"
+			c.readOnly = s.ColumnRawText(1)[0] // 0 or 1
+		}
+		err = s.Close()
+		if err != nil {
+			c.Close()
+			return nil, err
+		}
 	}
-
-	return conn{
-		conn:    c,
-		txBegin: txBegin,
-	}, nil
+	return c, nil
 }
 
 type conn struct {
@@ -91,6 +107,8 @@ type conn struct {
 	txBegin    string
 	txCommit   string
 	txRollback string
+	reusable   bool
+	readOnly   byte
 }
 
 var (
@@ -105,9 +123,8 @@ func (c conn) Close() error {
 	return c.conn.Close()
 }
 
-func (c conn) IsValid() (valid bool) {
-	r, err := c.conn.Pragma("locking_mode")
-	return err == nil && len(r) == 1 && r[0] == "normal"
+func (c conn) IsValid() bool {
+	return c.reusable
 }
 
 func (c conn) Begin() (driver.Tx, error) {
@@ -120,16 +137,12 @@ func (c conn) BeginTx(_ context.Context, opts driver.TxOptions) (driver.Tx, erro
 	c.txRollback = `ROLLBACK`
 
 	if opts.ReadOnly {
-		query_only, err := c.conn.Pragma("query_only")
-		if err != nil {
-			return nil, err
-		}
 		txBegin = `
 			BEGIN deferred;
 			PRAGMA query_only=on`
 		c.txCommit = `
 			ROLLBACK;
-			PRAGMA query_only=` + query_only[0]
+			PRAGMA query_only=` + string(c.readOnly)
 		c.txRollback = c.txCommit
 	}
 
@@ -140,14 +153,6 @@ func (c conn) BeginTx(_ context.Context, opts driver.TxOptions) (driver.Tx, erro
 		driver.IsolationLevel(sql.LevelDefault),
 		driver.IsolationLevel(sql.LevelSerializable):
 		break
-	case driver.IsolationLevel(sql.LevelReadUncommitted):
-		read_uncommitted, err := c.conn.Pragma("read_uncommitted")
-		if err != nil {
-			return nil, err
-		}
-		txBegin += `; PRAGMA read_uncommitted=on`
-		c.txCommit += `; PRAGMA read_uncommitted=` + read_uncommitted[0]
-		c.txRollback += `; PRAGMA read_uncommitted=` + read_uncommitted[0]
 	}
 
 	err := c.conn.Exec(txBegin)

driver/driver_test.go

@@ -147,16 +147,6 @@ func Test_BeginTx(t *testing.T) {
 		t.Error("want isolationErr")
 	}
 
-	tx, err := db.BeginTx(ctx, &sql.TxOptions{Isolation: sql.LevelReadUncommitted})
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = tx.Rollback()
-	if err != nil {
-		t.Fatal(err)
-	}
-
 	tx1, err := db.BeginTx(ctx, &sql.TxOptions{ReadOnly: true})
 	if err != nil {
 		t.Fatal(err)