Return not implemented error on vertical iterators for not used chunk…

… method.

Signed-off-by: Bartek Plotka <[email protected]>

querier.go

@@ -990,12 +990,10 @@ func (s *verticalChainedSeries) Iterator() SeriesIterator {
 	return newVerticalMergeSeriesIterator(s.series...)
 }
 
+// ChunkIterator is currently not implemented.
+// TODO(bwplotka): Implement once we will want to use chunks in vertical compaction.
 func (s *verticalChainedSeries) ChunkIterator() ChunkIterator {
-	ch := &chainedChunkIterator{chain: make([]ChunkIterator, 0, len(s.series))}
-	for _, s := range s.series {
-		ch.chain = append(ch.chain, s.ChunkIterator())
-	}
-	return ch
+	return errChunkIterator{err: errors.New("Not Implemented")}
 }
 
 // verticalMergeSeriesIterator implements a series iterater over a list
@@ -1244,6 +1242,14 @@ type ChunkIterator interface {
 	Err() error
 }
 
+type errChunkIterator struct {
+	err error
+}
+
+func (s errChunkIterator) Next() bool      { return false }
+func (s errChunkIterator) At() chunks.Meta { return chunks.Meta{} }
+func (s errChunkIterator) Err() error      { return s.err }
+
 type chunkIterator struct {
 	chunks []chunks.Meta // series in time order
 	i      int