eventstore: fix migrations annoyingly rerunning.

eventstore/mmm/migration.go

@@ -9,6 +9,8 @@ import (
 	"github.com/PowerDNS/lmdb-go/lmdb"
 )
 
+const target = 2
+
 func (il *IndexingLayer) migrate() error {
 	return il.lmdbEnv.Update(func(txn *lmdb.Txn) error {
 		val, err := txn.Get(il.settings, []byte("version"))
@@ -16,13 +18,11 @@ func (il *IndexingLayer) migrate() error {
 			return fmt.Errorf("failed to get db version: %w", err)
 		}
 
-		var version uint16 = 1
+		var version uint16 = target
 		if err == nil {
 			version = binary.BigEndian.Uint16(val)
 		}
 
-		const target = 2
-
 		// do the migrations in increasing steps (there is no rollback)
 		if version < target {
 			log.Printf("[mmm/%s] migration %d: reindex everything\n", il.name, target)