diff --git a/tsdb/ooo_head_read.go b/tsdb/ooo_head_read.go
index e1881aef86..aaaa249639 100644
--- a/tsdb/ooo_head_read.go
+++ b/tsdb/ooo_head_read.go
@@ -30,6 +30,13 @@ import (
 	"github.com/prometheus/prometheus/util/annotations"
 )
 
+var _ IndexReader = &HeadAndOOOIndexReader{}
+
+type HeadAndOOOIndexReader struct {
+	*headIndexReader            // A reference to the headIndexReader so we can reuse as many interface implementation as possible.
+	lastGarbageCollectedMmapRef chunks.ChunkDiskMapperRef
+}
+
 var _ chunkenc.Iterable = &mergedOOOChunks{}
 
 // mergedOOOChunks holds the list of iterables for overlapping chunks.
@@ -41,6 +48,39 @@ func (o mergedOOOChunks) Iterator(iterator chunkenc.Iterator) chunkenc.Iterator
 	return storage.ChainSampleIteratorFromIterables(iterator, o.chunkIterables)
 }
 
+func NewHeadAndOOOIndexReader(head *Head, mint, maxt int64, lastGarbageCollectedMmapRef chunks.ChunkDiskMapperRef) *HeadAndOOOIndexReader {
+	hr := &headIndexReader{
+		head: head,
+		mint: mint,
+		maxt: maxt,
+	}
+	return &HeadAndOOOIndexReader{hr, lastGarbageCollectedMmapRef}
+}
+
+func (oh *HeadAndOOOIndexReader) Series(ref storage.SeriesRef, builder *labels.ScratchBuilder, chks *[]chunks.Meta) error {
+	s := oh.head.series.getByID(chunks.HeadSeriesRef(ref))
+
+	if s == nil {
+		oh.head.metrics.seriesNotFound.Inc()
+		return storage.ErrNotFound
+	}
+	builder.Assign(s.labels())
+
+	if chks == nil {
+		return nil
+	}
+
+	s.Lock()
+	defer s.Unlock()
+	*chks = (*chks)[:0]
+
+	if s.ooo != nil {
+		return getOOOSeriesChunks(s, oh.mint, oh.maxt, oh.lastGarbageCollectedMmapRef, 0, true, chks)
+	}
+	getSeriesChunks(s, oh.mint, oh.maxt, chks)
+	return nil
+}
+
 // lastGarbageCollectedMmapRef gives the last mmap chunk that may be being garbage collected and so
 // any chunk at or before this ref will not be considered. 0 disables this check.
 //
@@ -126,6 +166,20 @@ func getOOOSeriesChunks(s *memSeries, mint, maxt int64, lastGarbageCollectedMmap
 	return nil
 }
 
+// LabelValues needs to be overridden from the headIndexReader implementation
+// so we can return labels within either in-order range or ooo range.
+func (oh *HeadAndOOOIndexReader) LabelValues(ctx context.Context, name string, matchers ...*labels.Matcher) ([]string, error) {
+	if oh.maxt < oh.head.MinTime() && oh.maxt < oh.head.MinOOOTime() || oh.mint > oh.head.MaxTime() && oh.mint > oh.head.MaxOOOTime() {
+		return []string{}, nil
+	}
+
+	if len(matchers) == 0 {
+		return oh.head.postings.LabelValues(ctx, name), nil
+	}
+
+	return labelValuesWithMatchers(ctx, oh, name, matchers...)
+}
+
 type chunkMetaAndChunkDiskMapperRef struct {
 	meta chunks.Meta
 	ref  chunks.ChunkDiskMapperRef
@@ -167,6 +221,64 @@ func lessByMinTimeAndMinRef(a, b chunks.Meta) int {
 	}
 }
 
+type HeadAndOOOChunkReader struct {
+	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, cr *headChunkReader, oooIsoState *oooIsolationState, maxMmapRef chunks.ChunkDiskMapperRef) *HeadAndOOOChunkReader {
+	return &HeadAndOOOChunkReader{
+		head:        head,
+		mint:        mint,
+		maxt:        maxt,
+		cr:          cr,
+		maxMmapRef:  maxMmapRef,
+		oooIsoState: oooIsoState,
+	}
+}
+
+func (cr *HeadAndOOOChunkReader) ChunkOrIterable(meta chunks.Meta) (chunkenc.Chunk, chunkenc.Iterable, error) {
+	sid, _, isOOO := unpackHeadChunkRef(meta.Ref)
+	if !isOOO {
+		return cr.cr.ChunkOrIterable(meta)
+	}
+
+	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.head.chunkDiskMapper, cr.cr, cr.mint, cr.maxt, cr.maxMmapRef)
+	s.Unlock()
+
+	return nil, mc, err
+}
+
+// Pass through special behaviour for current head chunk.
+func (cr *HeadAndOOOChunkReader) ChunkOrIterableWithCopy(meta chunks.Meta) (chunkenc.Chunk, chunkenc.Iterable, int64, error) {
+	_, _, isOOO := unpackHeadChunkRef(meta.Ref)
+	if !isOOO {
+		return cr.cr.ChunkOrIterableWithCopy(meta)
+	}
+	chk, iter, err := cr.ChunkOrIterable(meta)
+	return chk, iter, 0, err
+}
+
+func (cr *HeadAndOOOChunkReader) Close() error {
+	if cr.cr != nil && cr.cr.isoState != nil {
+		cr.cr.isoState.Close()
+	}
+	if cr.oooIsoState != nil {
+		cr.oooIsoState.Close()
+	}
+	return nil
+}
+
 type OOOCompactionHead struct {
 	head        *Head
 	lastMmapRef chunks.ChunkDiskMapperRef
@@ -473,112 +585,3 @@ func (q *HeadAndOOOChunkQuerier) Close() error {
 func (q *HeadAndOOOChunkQuerier) Select(ctx context.Context, sortSeries bool, hints *storage.SelectHints, matchers ...*labels.Matcher) storage.ChunkSeriesSet {
 	return selectChunkSeriesSet(ctx, sortSeries, hints, matchers, rangeHeadULID, q.index, q.chunkr, q.head.tombstones, q.mint, q.maxt)
 }
-
-type HeadAndOOOIndexReader struct {
-	*headIndexReader            // A reference to the headIndexReader so we can reuse as many interface implementation as possible.
-	lastGarbageCollectedMmapRef chunks.ChunkDiskMapperRef
-}
-
-func NewHeadAndOOOIndexReader(head *Head, mint, maxt int64, lastGarbageCollectedMmapRef chunks.ChunkDiskMapperRef) *HeadAndOOOIndexReader {
-	hr := &headIndexReader{
-		head: head,
-		mint: mint,
-		maxt: maxt,
-	}
-	return &HeadAndOOOIndexReader{hr, lastGarbageCollectedMmapRef}
-}
-
-func (oh *HeadAndOOOIndexReader) Series(ref storage.SeriesRef, builder *labels.ScratchBuilder, chks *[]chunks.Meta) error {
-	s := oh.head.series.getByID(chunks.HeadSeriesRef(ref))
-	if s == nil {
-		oh.head.metrics.seriesNotFound.Inc()
-		return storage.ErrNotFound
-	}
-	builder.Assign(s.labels())
-
-	if chks == nil {
-		return nil
-	}
-
-	s.Lock()
-	defer s.Unlock()
-	*chks = (*chks)[:0]
-
-	if s.ooo != nil {
-		return getOOOSeriesChunks(s, oh.mint, oh.maxt, oh.lastGarbageCollectedMmapRef, 0, true, chks)
-	}
-	getSeriesChunks(s, oh.mint, oh.maxt, chks)
-	return nil
-}
-
-// LabelValues needs to be overridden from the headIndexReader implementation
-// so we can return labels within either in-order range or ooo range.
-func (oh *HeadAndOOOIndexReader) LabelValues(ctx context.Context, name string, matchers ...*labels.Matcher) ([]string, error) {
-	if oh.maxt < oh.head.MinTime() && oh.maxt < oh.head.MinOOOTime() || oh.mint > oh.head.MaxTime() && oh.mint > oh.head.MaxOOOTime() {
-		return []string{}, nil
-	}
-
-	if len(matchers) == 0 {
-		return oh.head.postings.LabelValues(ctx, name), nil
-	}
-
-	return labelValuesWithMatchers(ctx, oh, name, matchers...)
-}
-
-type HeadAndOOOChunkReader struct {
-	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, cr *headChunkReader, oooIsoState *oooIsolationState, maxMmapRef chunks.ChunkDiskMapperRef) *HeadAndOOOChunkReader {
-	return &HeadAndOOOChunkReader{
-		head:        head,
-		mint:        mint,
-		maxt:        maxt,
-		cr:          cr,
-		maxMmapRef:  maxMmapRef,
-		oooIsoState: oooIsoState,
-	}
-}
-
-func (cr *HeadAndOOOChunkReader) ChunkOrIterable(meta chunks.Meta) (chunkenc.Chunk, chunkenc.Iterable, error) {
-	sid, _, isOOO := unpackHeadChunkRef(meta.Ref)
-	if !isOOO {
-		return cr.cr.ChunkOrIterable(meta)
-	}
-
-	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.head.chunkDiskMapper, cr.cr, cr.mint, cr.maxt, cr.maxMmapRef)
-	s.Unlock()
-
-	return nil, mc, err
-}
-
-// Pass through special behaviour for current head chunk.
-func (cr *HeadAndOOOChunkReader) ChunkOrIterableWithCopy(meta chunks.Meta) (chunkenc.Chunk, chunkenc.Iterable, int64, error) {
-	_, _, isOOO := unpackHeadChunkRef(meta.Ref)
-	if !isOOO {
-		return cr.cr.ChunkOrIterableWithCopy(meta)
-	}
-	chk, iter, err := cr.ChunkOrIterable(meta)
-	return chk, iter, 0, err
-}
-
-func (cr *HeadAndOOOChunkReader) Close() error {
-	if cr.cr != nil && cr.cr.isoState != nil {
-		cr.cr.isoState.Close()
-	}
-	if cr.oooIsoState != nil {
-		cr.oooIsoState.Close()
-	}
-	return nil
-}