From a51cdb04e6bed927a4d4badac969c70766a34ceb Mon Sep 17 00:00:00 2001
From: Nuno Cruces <ncruces@users.noreply.github.com>
Date: Sat, 18 Feb 2023 02:57:47 +0000
Subject: [PATCH] Exec fast path.

---
 driver/driver.go       | 41 ++++++++++++++++++++++++++++++++++++-----
 driver/error.go        |  5 ++++-
 driver/example_test.go | 10 +++-------
 3 files changed, 43 insertions(+), 13 deletions(-)

diff --git a/driver/driver.go b/driver/driver.go
index 091f016..fe0d989 100644
--- a/driver/driver.go
+++ b/driver/driver.go
@@ -18,7 +18,7 @@ func init() {
 type sqlite struct{}
 
 func (sqlite) Open(name string) (driver.Conn, error) {
-	c, err := sqlite3.OpenFlags(name, sqlite3.OPEN_READWRITE|sqlite3.OPEN_CREATE|sqlite3.OPEN_URI)
+	c, err := sqlite3.OpenFlags(name, sqlite3.OPEN_READWRITE|sqlite3.OPEN_CREATE|sqlite3.OPEN_URI|sqlite3.OPEN_EXRESCODE)
 	if err != nil {
 		return nil, err
 	}
@@ -38,10 +38,10 @@ type conn struct{ conn *sqlite3.Conn }
 
 var (
 	// Ensure these interfaces are implemented:
-	_ driver.Validator = conn{}
-	// _ driver.SessionResetter = conn{}
-	// _ driver.ExecerContext   = conn{}
+	_ driver.Validator     = conn{}
+	_ driver.ExecerContext = conn{}
 	// _ driver.ConnBeginTx     = conn{}
+	// _ driver.SessionResetter = conn{}
 )
 
 func (c conn) Close() error {
@@ -75,13 +75,44 @@ func (c conn) Rollback() error {
 }
 
 func (c conn) Prepare(query string) (driver.Stmt, error) {
-	s, _, err := c.conn.Prepare(query)
+	s, tail, err := c.conn.Prepare(query)
 	if err != nil {
 		return nil, err
 	}
+	if tail != "" {
+		// Check if the tail contains any SQL.
+		s, _, err := c.conn.Prepare(tail)
+		if err != nil {
+			return nil, err
+		}
+		if s != nil {
+			s.Close()
+			return nil, tailErr
+		}
+	}
 	return stmt{s, c.conn}, nil
 }
 
+func (c conn) ExecContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Result, error) {
+	if len(args) != 0 {
+		// Slow path.
+		return nil, driver.ErrSkip
+	}
+
+	ch := c.conn.SetInterrupt(ctx.Done())
+	defer c.conn.SetInterrupt(ch)
+
+	err := c.conn.Exec(query)
+	if err != nil {
+		return nil, err
+	}
+
+	return result{
+		int64(c.conn.LastInsertRowID()),
+		int64(c.conn.Changes()),
+	}, nil
+}
+
 func pragma(c *sqlite3.Conn, pragma string) (string, error) {
 	stmt, _, err := c.Prepare(`PRAGMA ` + pragma)
 	if err != nil {
diff --git a/driver/error.go b/driver/error.go
index cc8b2fd..240183f 100644
--- a/driver/error.go
+++ b/driver/error.go
@@ -4,4 +4,7 @@ type errorString string
 
 func (e errorString) Error() string { return string(e) }
 
-const assertErr = errorString("sqlite3: assertion failed")
+const (
+	assertErr = errorString("sqlite3: assertion failed")
+	tailErr   = errorString("sqlite3: multiple statements")
+)
diff --git a/driver/example_test.go b/driver/example_test.go
index e396bd5..749db76 100644
--- a/driver/example_test.go
+++ b/driver/example_test.go
@@ -66,18 +66,14 @@ type Album struct {
 }
 
 func setupDatabase() error {
-	_, err := db.Exec(`DROP TABLE IF EXISTS album`)
-	if err != nil {
-		return err
-	}
-
-	_, err = db.Exec(`
+	_, err := db.Exec(`
+		DROP TABLE IF EXISTS album;
 		CREATE TABLE album (
 			id         INTEGER PRIMARY KEY AUTOINCREMENT,
 			title      VARCHAR(128) NOT NULL,
 			artist     VARCHAR(255) NOT NULL,
 			price      DECIMAL(5,2) NOT NULL
-		)
+		);
 	`)
 	if err != nil {
 		return err