mount: Add tests for CommitJournal incremental checksumming

Author: saleemrashid

cmd/litefs/mount_test.go

@@ -298,6 +298,117 @@ func TestSingleNode_RecoverFromInitialRollback(t *testing.T) {
 	}
 }
 
+// Ensure that CommitJournal correctly computes the incremental checksum when
+// pages are modified multiple times.
+func TestSingleNode_JournalMultipleUpdates(t *testing.T) {
+	// This test only applies to the rollback journal, but it passes in WAL mode.
+
+	cmd := runMountCommand(t, newMountCommand(t, t.TempDir(), nil))
+	db := testingutil.OpenSQLDB(t, filepath.Join(cmd.Config.FUSE.Dir, "db"))
+
+	// Disable page cache so dirty pages are written immediately.
+	if _, err := db.Exec(`PRAGMA cache_size = 0`); err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := db.Exec(`CREATE TABLE t (x)`); err != nil {
+		t.Fatal(err)
+	}
+	for i := 0; i < 500; i++ {
+		if _, err := db.Exec(`INSERT INTO t VALUES (?)`, strings.Repeat("x", 60)); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() { _ = tx.Rollback() }()
+
+	// Update all pages (LiteFS will store the previous page checksum).
+	if _, err := tx.Exec(`UPDATE t SET x = ?`, strings.Repeat("y", 60)); err != nil {
+		t.Fatal(err)
+	}
+	// Update all pages again (LiteFS should not update the previous page checksum).
+	if _, err := tx.Exec(`UPDATE t SET x = ?`, strings.Repeat("z", 60)); err != nil {
+		t.Fatal(err)
+	}
+	if err := tx.Commit(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// Ensure that CommitJournal correctly computes the checksum when the commit
+// truncates dirty pages.
+func TestSingleNode_JournalTruncateDirtyPages(t *testing.T) {
+	if testingutil.IsWALMode() {
+		// The page count assertion will fail in WAL mode.
+		t.Skip("test only applies to rollback journal, skipping")
+	}
+
+	cmd := runMountCommand(t, newMountCommand(t, t.TempDir(), nil))
+	db := testingutil.OpenSQLDB(t, filepath.Join(cmd.Config.FUSE.Dir, "db"))
+
+	// Make sure the database is truncated on commit.
+	if _, err := db.Exec(`PRAGMA auto_vacuum = FULL`); err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := db.Exec(`CREATE TABLE t (id INTEGER PRIMARY KEY, x)`); err != nil {
+		t.Fatal(err)
+	}
+	for i := 0; i < 500; i++ {
+		if _, err := db.Exec(`INSERT INTO t (x) VALUES (?)`, strings.Repeat("x", 60)); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	var pageCount int
+	if err := db.QueryRow(`PRAGMA page_count`).Scan(&pageCount); err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("pre-commit pageCount = %d", pageCount)
+	if got, want := pageCount, 8; got <= want {
+		t.Fatalf("got %d pages, want more than %d", got, want)
+	}
+
+	tx, err := db.Begin()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() { _ = tx.Rollback() }()
+
+	// Make all pages dirty.
+	if _, err := tx.Exec(`UPDATE t SET x = ?`, strings.Repeat("y", 60)); err != nil {
+		t.Fatal(err)
+	}
+	// Truncate the database.
+	if _, err := tx.Exec(`DELETE FROM t WHERE id > ?`, 100); err != nil {
+		t.Fatal(err)
+	}
+	if err := tx.Commit(); err != nil {
+		t.Fatal(err)
+	}
+
+	var count int
+	if err := db.QueryRow(`SELECT COUNT(*) FROM t`).Scan(&count); err != nil {
+		t.Fatal(err)
+	}
+	if got, want := count, 100; got != want {
+		t.Fatalf("count=%d, want %d", got, want)
+	}
+
+	// Make sure the database was truncated.
+	if err := db.QueryRow(`PRAGMA page_count`).Scan(&pageCount); err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("post-commit pageCount = %d", pageCount)
+	if got, want := pageCount, 8; got >= want {
+		t.Fatalf("got %d pages, want less than %d", got, want)
+	}
+}
+
 func TestSingleNode_DropDB(t *testing.T) {
 	cmd0 := runMountCommand(t, newMountCommand(t, t.TempDir(), nil))
 	dsn := filepath.Join(cmd0.Config.FUSE.Dir, "db")