fix: disable empty vlog deletion on ReadOnly mode

Author: Naelpuissant

value.go

@@ -575,7 +575,6 @@ func (vlog *valueLog) open(db *DB) error {
 		lf, ok := vlog.filesMap[fid]
 		y.AssertTrue(ok)
 
-		// Just open in RDWR mode. This should not create a new log file.
 		lf.opt = vlog.opt
 		flags := os.O_RDWR
 		if vlog.opt.ReadOnly {
@@ -586,7 +585,7 @@ func (vlog *valueLog) open(db *DB) error {
 			return y.Wrapf(err, "Open existing file: %q", lf.path)
 		}
 		// We shouldn't delete the maxFid file.
-		if lf.size.Load() == vlogHeaderSize && fid != vlog.maxFid {
+		if lf.size.Load() == vlogHeaderSize && fid != vlog.maxFid && !vlog.opt.ReadOnly {
 			vlog.opt.Infof("Deleting empty file: %s", lf.path)
 			if err := lf.Delete(); err != nil {
 				return y.Wrapf(err, "while trying to delete empty file: %s", lf.path)