lib/db: Remove Badger experiment (#7413)

lib/db/backend/backend.go

@@ -8,12 +8,7 @@ package backend
 
 import (
 	"errors"
-	"os"
-	"strings"
 	"sync"
-	"time"
-
-	"github.com/syncthing/syncthing/lib/locations"
 )
 
 // CommitHook is a function that is executed before a WriteTransaction is
@@ -131,10 +126,6 @@ const (
 )
 
 func Open(path string, tuning Tuning) (Backend, error) {
-	if err := maybeCopyDatabase(path, strings.Replace(path, locations.LevelDBDir, locations.BadgerDir, 1), OpenLevelDBAuto, OpenBadger); err != nil {
-		return nil, err
-	}
-
 	return OpenLevelDB(path, tuning)
 }
 
@@ -209,70 +200,3 @@ func (cg *closeWaitGroup) CloseWait() {
 	cg.closeMut.Unlock()
 	cg.WaitGroup.Wait()
 }
-
-type opener func(path string) (Backend, error)
-
-// maybeCopyDatabase copies the database if the destination doesn't exist
-// but the source does.
-func maybeCopyDatabase(toPath, fromPath string, toOpen, fromOpen opener) error {
-	if _, err := os.Lstat(toPath); !os.IsNotExist(err) {
-		// Destination database exists (or is otherwise unavailable), do not
-		// attempt to overwrite it.
-		return nil
-	}
-
-	if _, err := os.Lstat(fromPath); err != nil {
-		// Source database is not available, so nothing to copy
-		return nil
-	}
-
-	fromDB, err := fromOpen(fromPath)
-	if err != nil {
-		return err
-	}
-	defer fromDB.Close()
-
-	toDB, err := toOpen(toPath)
-	if err != nil {
-		// That's odd, but it will be handled & reported in the usual path
-		// so we can ignore it here.
-		return err
-	}
-	defer toDB.Close()
-
-	l.Infoln("Copying database for format conversion...")
-	if err := copyBackend(toDB, fromDB); err != nil {
-		return err
-	}
-
-	// Move the old database out of the way to mark it as migrated.
-	fromDB.Close()
-	_ = os.Rename(fromPath, fromPath+".migrated."+time.Now().Format("20060102150405"))
-	return nil
-}
-
-func copyBackend(to, from Backend) error {
-	srcIt, err := from.NewPrefixIterator(nil)
-	if err != nil {
-		return err
-	}
-	defer srcIt.Release()
-
-	dstTx, err := to.NewWriteTransaction()
-	if err != nil {
-		return err
-	}
-	defer dstTx.Release()
-
-	for srcIt.Next() {
-		if err := dstTx.Put(srcIt.Key(), srcIt.Value()); err != nil {
-			return err
-		}
-	}
-	if srcIt.Error() != nil {
-		return err
-	}
-	srcIt.Release()
-
-	return dstTx.Commit()
-}