TSDB: NewHeadAndOOOChunkReader takes headChunkReader

So we can pass nil and have it read just OOO chunks.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

tsdb/ooo_head_read.go

@@ -514,13 +514,18 @@ type HeadAndOOOQuerier struct {
 }
 
 func NewHeadAndOOOQuerier(mint, maxt int64, head *Head, oooIsoState *oooIsolationState, querier storage.Querier) storage.Querier {
-	isoState := head.iso.State(mint, maxt)
+	cr := &headChunkReader{
+		head:     head,
+		mint:     mint,
+		maxt:     maxt,
+		isoState: head.iso.State(mint, maxt),
+	}
 	return &HeadAndOOOQuerier{
 		mint:    mint,
 		maxt:    maxt,
 		head:    head,
 		index:   NewHeadAndOOOIndexReader(head, mint, maxt, oooIsoState.minRef),
-		chunkr:  NewHeadAndOOOChunkReader(head, mint, maxt, isoState, oooIsoState, 0),
+		chunkr:  NewHeadAndOOOChunkReader(head, mint, maxt, cr, oooIsoState, 0),
 		querier: querier,
 	}
 }
@@ -552,13 +557,18 @@ type HeadAndOOOChunkQuerier struct {
 }
 
 func NewHeadAndOOOChunkQuerier(mint, maxt int64, head *Head, oooIsoState *oooIsolationState, querier storage.ChunkQuerier) storage.ChunkQuerier {
-	isoState := head.iso.State(mint, maxt)
+	cr := &headChunkReader{
+		head:     head,
+		mint:     mint,
+		maxt:     maxt,
+		isoState: head.iso.State(mint, maxt),
+	}
 	return &HeadAndOOOChunkQuerier{
 		mint:    mint,
 		maxt:    maxt,
 		head:    head,
 		index:   NewHeadAndOOOIndexReader(head, mint, maxt, oooIsoState.minRef),
-		chunkr:  NewHeadAndOOOChunkReader(head, mint, maxt, isoState, oooIsoState, 0),
+		chunkr:  NewHeadAndOOOChunkReader(head, mint, maxt, cr, oooIsoState, 0),
 		querier: querier,
 	}
 }
@@ -618,19 +628,19 @@ func (oh *HeadAndOOOIndexReader) Series(ref storage.SeriesRef, builder *labels.S
 }
 
 type HeadAndOOOChunkReader struct {
-	cr          headChunkReader
+	head        *Head
+	mint, maxt  int64
+	cr          *headChunkReader // If nil, only read OOO chunks.
 	maxMmapRef  chunks.ChunkDiskMapperRef
 	oooIsoState *oooIsolationState
 }
 
-func NewHeadAndOOOChunkReader(head *Head, mint, maxt int64, isoState *isolationState, oooIsoState *oooIsolationState, maxMmapRef chunks.ChunkDiskMapperRef) *HeadAndOOOChunkReader {
+func NewHeadAndOOOChunkReader(head *Head, mint, maxt int64, cr *headChunkReader, oooIsoState *oooIsolationState, maxMmapRef chunks.ChunkDiskMapperRef) *HeadAndOOOChunkReader {
 	return &HeadAndOOOChunkReader{
-		cr: headChunkReader{
-			head:     head,
-			mint:     mint,
-			maxt:     maxt,
-			isoState: isoState,
-		},
+		head:        head,
+		mint:        mint,
+		maxt:        maxt,
+		cr:          cr,
 		maxMmapRef:  maxMmapRef,
 		oooIsoState: oooIsoState,
 	}
@@ -642,14 +652,14 @@ func (cr *HeadAndOOOChunkReader) ChunkOrIterable(meta chunks.Meta) (chunkenc.Chu
 		return cr.cr.ChunkOrIterable(meta)
 	}
 
-	s := cr.cr.head.series.getByID(sid)
+	s := cr.head.series.getByID(sid)
 	// This means that the series has been garbage collected.
 	if s == nil {
 		return nil, nil, storage.ErrNotFound
 	}
 
 	s.Lock()
-	mc, err := s.oooMergedChunks(meta, cr.cr.head.chunkDiskMapper, &cr.cr, cr.cr.mint, cr.cr.maxt, cr.maxMmapRef)
+	mc, err := s.oooMergedChunks(meta, cr.head.chunkDiskMapper, cr.cr, cr.mint, cr.maxt, cr.maxMmapRef)
 	s.Unlock()
 
 	return nil, mc, err
@@ -666,7 +676,7 @@ func (cr *HeadAndOOOChunkReader) ChunkOrIterableWithCopy(meta chunks.Meta) (chun
 }
 
 func (cr *HeadAndOOOChunkReader) Close() error {
-	if cr.cr.isoState != nil {
+	if cr.cr != nil && cr.cr.isoState != nil {
 		cr.cr.isoState.Close()
 	}
 	if cr.oooIsoState != nil {