Dont write empty blocks

Signed-off-by: Ganesh Vernekar <[email protected]>

compact.go

@@ -508,8 +508,13 @@ func (c *LeveledCompactor) write(dest string, meta *BlockMeta, blocks ...BlockRe
 	df = nil
 
 	// Block successfully written, make visible and remove old ones.
-	if err := renameFile(tmp, dir); err != nil {
-		return errors.Wrap(err, "rename block dir")
+	if meta.Stats.NumSamples > 0 {
+		// Rename to a new block only if we have samples.
+		if err := renameFile(tmp, dir); err != nil {
+			return errors.Wrap(err, "rename block dir")
+		}
+	} else if err := os.RemoveAll(tmp); err != nil {
+		return errors.Wrap(err, "remove tmp folder after empty block failed")
 	}
 
 	return nil