diff --git a/block.go b/block.go
index e8985a7f2..dcc2e58ec 100644
--- a/block.go
+++ b/block.go
@@ -13,9 +13,9 @@ import (
 
 // Block handles reads against a block of time series data within a time window.
 type block interface {
-	Querier(mint, maxt int64) Querier
-
 	interval() (int64, int64)
+	index() IndexReader
+	series() SeriesReader
 }
 
 type BlockStats struct {
@@ -34,8 +34,8 @@ const (
 type persistedBlock struct {
 	chunksf, indexf *mmapFile
 
-	chunks *seriesReader
-	index  *indexReader
+	chunkr *seriesReader
+	indexr *indexReader
 
 	stats BlockStats
 }
@@ -70,8 +70,8 @@ func newPersistedBlock(path string) (*persistedBlock, error) {
 	pb := &persistedBlock{
 		chunksf: chunksf,
 		indexf:  indexf,
-		chunks:  sr,
-		index:   ir,
+		chunkr:  sr,
+		indexr:  ir,
 		stats:   stats,
 	}
 	return pb, nil
@@ -87,13 +87,12 @@ func (pb *persistedBlock) Close() error {
 	return err1
 }
 
-func (pb *persistedBlock) Querier(mint, maxt int64) Querier {
-	return &blockQuerier{
-		mint:   mint,
-		maxt:   maxt,
-		index:  pb.index,
-		series: pb.chunks,
-	}
+func (pb *persistedBlock) index() IndexReader {
+	return pb.indexr
+}
+
+func (pb *persistedBlock) series() SeriesReader {
+	return pb.chunkr
 }
 
 func (pb *persistedBlock) interval() (int64, int64) {
diff --git a/compact.go b/compact.go
index 3ef779361..c6539179f 100644
--- a/compact.go
+++ b/compact.go
@@ -57,7 +57,7 @@ func (c *compactor) close() error {
 	return nil
 }
 
-func (c *compactor) compact(dir string, a, b *persistedBlock) error {
+func (c *compactor) compact(dir string, a, b block) error {
 	if err := os.MkdirAll(dir, 0777); err != nil {
 		return err
 	}
@@ -77,23 +77,32 @@ func (c *compactor) compact(dir string, a, b *persistedBlock) error {
 	defer index.Close()
 	defer series.Close()
 
-	aall, err := a.index.Postings("", "")
+	aall, err := a.index().Postings("", "")
 	if err != nil {
 		return err
 	}
-	ball, err := b.index.Postings("", "")
+	ball, err := b.index().Postings("", "")
 	if err != nil {
 		return err
 	}
 
 	set, err := newCompactionMerger(
-		newCompactionSeriesSet(a.index, a.chunks, aall),
-		newCompactionSeriesSet(b.index, b.chunks, ball),
+		newCompactionSeriesSet(a.index(), a.series(), aall),
+		newCompactionSeriesSet(b.index(), b.series(), ball),
 	)
 	if err != nil {
 		return err
 	}
 
+	astats, err := a.index().Stats()
+	if err != nil {
+		return err
+	}
+	bstats, err := a.index().Stats()
+	if err != nil {
+		return err
+	}
+
 	// We fully rebuild the postings list index from merged series.
 	var (
 		postings = &memPostings{m: make(map[term][]uint32, 512)}
@@ -101,9 +110,9 @@ func (c *compactor) compact(dir string, a, b *persistedBlock) error {
 		i        = uint32(0)
 	)
 	stats := BlockStats{
-		MinTime:     a.stats.MinTime,
-		MaxTime:     b.stats.MaxTime,
-		SampleCount: a.stats.SampleCount + b.stats.SampleCount,
+		MinTime:     astats.MinTime,
+		MaxTime:     bstats.MaxTime,
+		SampleCount: astats.SampleCount + bstats.SampleCount,
 	}
 
 	for set.Next() {
diff --git a/head.go b/head.go
index 01110f1a2..171c55290 100644
--- a/head.go
+++ b/head.go
@@ -66,9 +66,12 @@ func (h *HeadBlock) Close() error {
 	return h.wal.Close()
 }
 
-// Querier returns a new querier over the head block.
-func (h *HeadBlock) Querier(mint, maxt int64) Querier {
-	return newBlockQuerier(h, h, mint, maxt)
+func (h *HeadBlock) index() IndexReader {
+	return h
+}
+
+func (h *HeadBlock) series() SeriesReader {
+	return h
 }
 
 // Chunk returns the chunk for the reference number.
diff --git a/querier.go b/querier.go
index 1d53f47f6..0532516b6 100644
--- a/querier.go
+++ b/querier.go
@@ -148,7 +148,12 @@ func (s *Shard) Querier(mint, maxt int64) Querier {
 	}
 
 	for _, b := range blocks {
-		sq.blocks = append(sq.blocks, b.Querier(mint, maxt))
+		sq.blocks = append(sq.blocks, &blockQuerier{
+			mint:   mint,
+			maxt:   maxt,
+			index:  b.index(),
+			series: b.series(),
+		})
 	}
 
 	return sq