From 0df7c424a1315bec26c96de4ffae9cefce3ae116 Mon Sep 17 00:00:00 2001
From: dawn <dawn@tangled.org>
Date: Wed, 21 Oct 2026 22:06:44 +0300
Subject: [PATCH] orm: don't take the write lock for a migration that is
 already applied

Signed-off-by: dawn <dawn@tangled.org>
---
 orm/orm.go                | 10 +++++++++
 orm/run_migration_test.go | 47 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+)
 create mode 100644 orm/run_migration_test.go

diff --git a/orm/orm.go b/orm/orm.go
index 927183787..99f8e831b 100644
--- a/orm/orm.go
+++ b/orm/orm.go
@@ -26,6 +26,16 @@ type migrationFn = func(*sql.Tx) error
 func RunMigration(c *sql.Conn, logger *slog.Logger, name string, migrationFn migrationFn) error {
 	logger = logger.With("migration", name)
 
+	// check first, or a busy db fails every boot on the write lock
+	var applied bool
+	if err := c.QueryRowContext(context.Background(), "select exists (select 1 from migrations where name = ?)", name).Scan(&applied); err != nil {
+		return err
+	}
+	if applied {
+		logger.Warn("skipped migration, already applied")
+		return nil
+	}
+
 	tx, err := c.BeginTx(context.Background(), nil)
 	if err != nil {
 		return err
diff --git a/orm/run_migration_test.go b/orm/run_migration_test.go
new file mode 100644
index 000000000..451fce086
--- /dev/null
+++ b/orm/run_migration_test.go
@@ -0,0 +1,47 @@
+package orm
+
+import (
+	"context"
+	"database/sql"
+	"io"
+	"log/slog"
+	"path/filepath"
+	"testing"
+)
+
+func TestAppliedMigrationDoesNotNeedTheWriteLock(t *testing.T) {
+	ctx := context.Background()
+	dsn := "file:" + filepath.Join(t.TempDir(), "orm.db") + "?_txlock=immediate&_busy_timeout=200"
+	db, err := sql.Open("sqlite3", dsn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { db.Close() })
+	if _, err := db.Exec(`
+		create table migrations (id integer primary key autoincrement, name text unique);
+		insert into migrations (name) values ('done');
+	`); err != nil {
+		t.Fatal(err)
+	}
+
+	holder, err := db.BeginTx(ctx, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer holder.Rollback()
+
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
+	ran := false
+	err = RunMigration(conn, logger, "done", func(*sql.Tx) error {
+		ran = true
+		return nil
+	})
+	if err != nil || ran {
+		t.Fatalf("applied migration with the write lock held = %v, ran %v, want it skipped", err, ran)
+	}
+}
-- 
2.54.0