.

go/zodb/storage/demo/demo_test.go

@@ -41,7 +41,7 @@ import (
 
 // DemoData represents data for a demo: storage.
 type DemoData struct {
-	base string // path for  base.fs
+	base string // url for   base.fs
 	δ    string // ----/---- δ.fs
 }
 
@@ -56,7 +56,7 @@ type tOptions struct {
 	Preload string // preload database with data from this location
 }
 
-// withDemoData tests f with all kind of demo data splits.
+// withDemoData tests f with all kinds of opt.Preload data split into base + δ.
 func withDemoData(t *testing.T, f func(t *testing.T, ddat *DemoData), optv ...tOptions) {
 	t.Helper()
 	X := xtesting.FatalIf(t)
@@ -89,18 +89,14 @@ func withDemoData(t *testing.T, f func(t *testing.T, ddat *DemoData), optv ...tO
 		pos int      // where this transaction starts in the dump
 	}
 	var txnv []zdumpTxn
-//	fmt.Printf("%s\n\n\n", zdump)
 	for _, m := range txnRe.FindAllStringSubmatchIndex(zdump, -1) {
-//		fmt.Println(m)
-		// [m[0]:m[1]] refer to whole txn line
+		// [m[0]:m[1]] refers to whole txn line
 		__ := zdump[m[2]:m[3]]
 		tid, err := zodb.ParseTid(__); X(err)
 		txnv = append(txnv, zdumpTxn{tid, m[0]})
 	}
 
-//	fmt.Printf("\n\n\ntxnv: %v\n", txnv)
-
-	// verify on all combinations of preload being split into base+δ 
+	// verify f on all combinations of preload being split into base+δ
 	work := xtempdir(t)
 	defer os.RemoveAll(work)
 	test1 := func(δstart zodb.Tid, zdumpBase, zdumpδ string) {
@@ -116,7 +112,10 @@ func withDemoData(t *testing.T, f func(t *testing.T, ddat *DemoData), optv ...tO
 			ddat := &DemoData{base, δ}
 
 			_, err = xtesting.ZPyRestore(base, zdumpBase);  X(err)
-			// XXX + explain why demo instead of δ (restoring copy without original present fails)
+			// restore δ part via `demo:(base)/(δ)` - not `file:δ`.
+			// The reason we do this is because restoring δ via
+			// just its file will fail when restoring copy data
+			// record with copy_from transaction being in base.
 			_, err = xtesting.ZPyRestore(ddat.URL(), zdumpδ);  X(err)
 
 			f(t, ddat)

go/zodb/storage/fs1/filestorage.go

-// Copyright (C) 2017-2020  Nexedi SA and Contributors.
+// Copyright (C) 2017-2021  Nexedi SA and Contributors.
 //                          Kirill Smelkov <kirr@nexedi.com>
 //
 // This program is free software: you can Use, Study, Modify and Redistribute
@@ -132,7 +132,7 @@ func (fs *FileStorage) LastOid(_ context.Context) (zodb.Oid, error) {
 }
 
 func (fs *FileStorage) URL() string {
-	return fs.file.Name()
+	return fs.file.Name() // XXX + file://
 }
 
 // freelist(DataHeader)