Add sqlutil package

Provides SQL-related helpers, mostly targeted to a simple sqlite embedded database.

sqlutil/db.go

@@ -11,7 +11,7 @@ import (
 )
 
 // DebugMigrations can be set to true to dump statements to stderr.
-var DebugMigrations = true
+var DebugMigrations bool
 
 const defaultOptions = "?cache=shared&_busy_timeout=10000&_journal=WAL&_sync=OFF"
 
@@ -67,6 +67,7 @@ func migrate(db *sql.DB, migrations []func(*sql.Tx) error) error {
 
 	if idx == len(migrations) {
 		// Already fully migrated, nothing needed.
+		return nil
 	} else if idx > len(migrations) {
 		return fmt.Errorf("database is at version %d, which is more recent than this binary understands", idx)
 	}
@@ -77,10 +78,13 @@ func migrate(db *sql.DB, migrations []func(*sql.Tx) error) error {
 		}
 	}
 
-	// For some reason, ? substitution doesn't work in PRAGMA
-	// statements, sqlite reports a parse error.
-	if _, err := tx.Exec(fmt.Sprintf("PRAGMA user_version=%d", len(migrations))); err != nil {
-		return fmt.Errorf("recording new DB version: %w", err)
+	if n := len(migrations); n > 0 {
+		// For some reason, ? substitution doesn't work in PRAGMA
+		// statements, sqlite reports a parse error.
+		if _, err := tx.Exec(fmt.Sprintf("PRAGMA user_version=%d", n)); err != nil {
+			return fmt.Errorf("recording new DB version: %w", err)
+		}
+		log.Printf("db migration: upgraded schema version %d -> %d", idx, n)
 	}
 
 	return tx.Commit()