lib/model: Don't use empty folder cfg for index sender (fixes #7649) (#7671)

lib/db/lowlevel.go

@@ -587,6 +587,18 @@ func (db *Lowlevel) dropFolderIndexIDs(folder []byte) error {
 	return t.Commit()
 }
 
+func (db *Lowlevel) dropIndexIDs() error {
+	t, err := db.newReadWriteTransaction()
+	if err != nil {
+		return err
+	}
+	defer t.close()
+	if err := t.deleteKeyPrefix([]byte{KeyTypeIndexID}); err != nil {
+		return err
+	}
+	return t.Commit()
+}
+
 func (db *Lowlevel) dropMtimes(folder []byte) error {
 	key, err := db.keyer.GenerateMtimesKey(nil, folder)
 	if err != nil {

lib/db/schemaupdater.go

@@ -20,7 +20,7 @@ import (
 // do not put restrictions on downgrades (e.g. for repairs after a bugfix).
 const (
 	dbVersion             = 14
-	dbMigrationVersion    = 17
+	dbMigrationVersion    = 18
 	dbMinSyncthingVersion = "v1.9.0"
 )
 
@@ -102,6 +102,7 @@ func (db *schemaUpdater) updateSchema() error {
 		{14, 14, "v1.9.0", db.updateSchemaTo14},
 		{14, 16, "v1.9.0", db.checkRepairMigration},
 		{14, 17, "v1.9.0", db.migration17},
+		{14, 18, "v1.9.0", db.dropIndexIDsMigration},
 	}
 
 	for _, m := range migrations {
@@ -831,6 +832,10 @@ func (db *schemaUpdater) migration17(prev int) error {
 	return nil
 }
 
+func (db *schemaUpdater) dropIndexIDsMigration(_ int) error {
+	return db.dropIndexIDs()
+}
+
 func (db *schemaUpdater) rewriteGlobals(t readWriteTransaction) error {
 	it, err := t.NewPrefixIterator([]byte{KeyTypeGlobal})
 	if err != nil {

lib/db/set.go

@@ -451,21 +451,12 @@ func DropDeltaIndexIDs(db *Lowlevel) {
 	}
 	opStr := "DropDeltaIndexIDs"
 	l.Debugf(opStr)
-	dbi, err := db.NewPrefixIterator([]byte{KeyTypeIndexID})
+	err := db.dropIndexIDs()
 	if backend.IsClosed(err) {
 		return
 	} else if err != nil {
 		fatalError(err, opStr, db)
 	}
-	defer dbi.Release()
-	for dbi.Next() {
-		if err := db.Delete(dbi.Key()); err != nil && !backend.IsClosed(err) {
-			fatalError(err, opStr, db)
-		}
-	}
-	if err := dbi.Error(); err != nil && !backend.IsClosed(err) {
-		fatalError(err, opStr, db)
-	}
 }
 
 func normalizeFilenamesAndDropDuplicates(fs []protocol.FileInfo) []protocol.FileInfo {