diff --git a/tsdb/block_test.go b/tsdb/block_test.go
index 584037c57..41d022e91 100644
--- a/tsdb/block_test.go
+++ b/tsdb/block_test.go
@@ -266,7 +266,10 @@ func TestBlockSize(t *testing.T) {
 
 // createBlock creates a block with given set of series and returns its dir.
 func createBlock(tb testing.TB, dir string, series []Series) string {
-	head := createHead(tb, series)
+	return createBlockFromHead(tb, dir, createHead(tb, series))
+}
+
+func createBlockFromHead(tb testing.TB, dir string, head *Head) string {
 	compactor, err := NewLeveledCompactor(context.Background(), nil, log.NewNopLogger(), []int64{1000000}, nil)
 	testutil.Ok(tb, err)
 
diff --git a/tsdb/head_bench_test.go b/tsdb/head_bench_test.go
index 6fee2122f..0f807814e 100644
--- a/tsdb/head_bench_test.go
+++ b/tsdb/head_bench_test.go
@@ -48,73 +48,3 @@ func BenchmarkHeadStripeSeriesCreateParallel(b *testing.B) {
 		}
 	})
 }
-
-func BenchmarkHeadPostingForMatchers(b *testing.B) {
-	h, err := NewHead(nil, nil, nil, 1000)
-	testutil.Ok(b, err)
-	defer func() {
-		testutil.Ok(b, h.Close())
-	}()
-
-	var ref uint64
-
-	addSeries := func(l labels.Labels) {
-		ref++
-		h.getOrCreateWithID(ref, l.Hash(), l)
-	}
-
-	for n := 0; n < 10; n++ {
-		for i := 0; i < 100000; i++ {
-			addSeries(labels.FromStrings("i", strconv.Itoa(i), "n", strconv.Itoa(n), "j", "foo"))
-			// Have some series that won't be matched, to properly test inverted matches.
-			addSeries(labels.FromStrings("i", strconv.Itoa(i), "n", strconv.Itoa(n), "j", "bar"))
-			addSeries(labels.FromStrings("i", strconv.Itoa(i), "n", "0_"+strconv.Itoa(n), "j", "bar"))
-			addSeries(labels.FromStrings("i", strconv.Itoa(i), "n", "1_"+strconv.Itoa(n), "j", "bar"))
-			addSeries(labels.FromStrings("i", strconv.Itoa(i), "n", "2_"+strconv.Itoa(n), "j", "foo"))
-		}
-	}
-
-	n1 := labels.MustNewMatcher(labels.MatchEqual, "n", "1")
-
-	jFoo := labels.MustNewMatcher(labels.MatchEqual, "j", "foo")
-	jNotFoo := labels.MustNewMatcher(labels.MatchNotEqual, "j", "foo")
-
-	iStar := labels.MustNewMatcher(labels.MatchRegexp, "i", "^.*$")
-	iPlus := labels.MustNewMatcher(labels.MatchRegexp, "i", "^.+$")
-	i1Plus := labels.MustNewMatcher(labels.MatchRegexp, "i", "^1.+$")
-	iEmptyRe := labels.MustNewMatcher(labels.MatchRegexp, "i", "^$")
-	iNotEmpty := labels.MustNewMatcher(labels.MatchNotEqual, "i", "")
-	iNot2 := labels.MustNewMatcher(labels.MatchNotEqual, "n", "2")
-	iNot2Star := labels.MustNewMatcher(labels.MatchNotRegexp, "i", "^2.*$")
-
-	cases := []struct {
-		name     string
-		matchers []*labels.Matcher
-	}{
-		{`n="1"`, []*labels.Matcher{n1}},
-		{`n="1",j="foo"`, []*labels.Matcher{n1, jFoo}},
-		{`j="foo",n="1"`, []*labels.Matcher{jFoo, n1}},
-		{`n="1",j!="foo"`, []*labels.Matcher{n1, jNotFoo}},
-		{`i=~".*"`, []*labels.Matcher{iStar}},
-		{`i=~".+"`, []*labels.Matcher{iPlus}},
-		{`i=~""`, []*labels.Matcher{iEmptyRe}},
-		{`i!=""`, []*labels.Matcher{iNotEmpty}},
-		{`n="1",i=~".*",j="foo"`, []*labels.Matcher{n1, iStar, jFoo}},
-		{`n="1",i=~".*",i!="2",j="foo"`, []*labels.Matcher{n1, iStar, iNot2, jFoo}},
-		{`n="1",i!=""`, []*labels.Matcher{n1, iNotEmpty}},
-		{`n="1",i!="",j="foo"`, []*labels.Matcher{n1, iNotEmpty, jFoo}},
-		{`n="1",i=~".+",j="foo"`, []*labels.Matcher{n1, iPlus, jFoo}},
-		{`n="1",i=~"1.+",j="foo"`, []*labels.Matcher{n1, i1Plus, jFoo}},
-		{`n="1",i=~".+",i!="2",j="foo"`, []*labels.Matcher{n1, iPlus, iNot2, jFoo}},
-		{`n="1",i=~".+",i!~"2.*",j="foo"`, []*labels.Matcher{n1, iPlus, iNot2Star, jFoo}},
-	}
-
-	for _, c := range cases {
-		b.Run(c.name, func(b *testing.B) {
-			for i := 0; i < b.N; i++ {
-				_, err := PostingsForMatchers(h.indexRange(0, 1000), c.matchers...)
-				testutil.Ok(b, err)
-			}
-		})
-	}
-}
diff --git a/tsdb/querier_bench_test.go b/tsdb/querier_bench_test.go
new file mode 100644
index 000000000..48e73fe85
--- /dev/null
+++ b/tsdb/querier_bench_test.go
@@ -0,0 +1,125 @@
+// Copyright 2018 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tsdb
+
+import (
+	"io/ioutil"
+	"os"
+	"strconv"
+	"testing"
+
+	"github.com/prometheus/prometheus/pkg/labels"
+	"github.com/prometheus/prometheus/util/testutil"
+)
+
+// Make entries ~50B in size, to emulate real-world high cardinality.
+const (
+	postingsBenchSuffix = "aaaaaaaaaabbbbbbbbbbccccccccccdddddddddd"
+)
+
+func BenchmarkPostingsForMatchers(b *testing.B) {
+	h, err := NewHead(nil, nil, nil, 1000)
+	testutil.Ok(b, err)
+	defer func() {
+		testutil.Ok(b, h.Close())
+	}()
+
+	app := h.Appender()
+	addSeries := func(l labels.Labels) {
+		app.Add(l, 0, 0)
+	}
+
+	for n := 0; n < 10; n++ {
+		for i := 0; i < 100000; i++ {
+			addSeries(labels.FromStrings("i", strconv.Itoa(i)+postingsBenchSuffix, "n", strconv.Itoa(n)+postingsBenchSuffix, "j", "foo"))
+			// Have some series that won't be matched, to properly test inverted matches.
+			addSeries(labels.FromStrings("i", strconv.Itoa(i)+postingsBenchSuffix, "n", strconv.Itoa(n)+postingsBenchSuffix, "j", "bar"))
+			addSeries(labels.FromStrings("i", strconv.Itoa(i)+postingsBenchSuffix, "n", "0_"+strconv.Itoa(n)+postingsBenchSuffix, "j", "bar"))
+			addSeries(labels.FromStrings("i", strconv.Itoa(i)+postingsBenchSuffix, "n", "1_"+strconv.Itoa(n)+postingsBenchSuffix, "j", "bar"))
+			addSeries(labels.FromStrings("i", strconv.Itoa(i)+postingsBenchSuffix, "n", "2_"+strconv.Itoa(n)+postingsBenchSuffix, "j", "foo"))
+		}
+	}
+	testutil.Ok(b, app.Commit())
+
+	ir, err := h.Index()
+	testutil.Ok(b, err)
+	b.Run("Head", func(b *testing.B) {
+		benchmarkPostingsForMatchers(b, ir)
+	})
+
+	tmpdir, err := ioutil.TempDir("", "test_benchpostingsformatchers")
+	testutil.Ok(b, err)
+	defer func() {
+		testutil.Ok(b, os.RemoveAll(tmpdir))
+	}()
+
+	blockdir := createBlockFromHead(b, tmpdir, h)
+	block, err := OpenBlock(nil, blockdir, nil)
+	testutil.Ok(b, err)
+	defer func() {
+		testutil.Ok(b, block.Close())
+	}()
+	ir, err = block.Index()
+	testutil.Ok(b, err)
+	defer ir.Close()
+	b.Run("Block", func(b *testing.B) {
+		benchmarkPostingsForMatchers(b, ir)
+	})
+}
+
+func benchmarkPostingsForMatchers(b *testing.B, ir IndexReader) {
+	n1 := labels.MustNewMatcher(labels.MatchEqual, "n", "1"+postingsBenchSuffix)
+
+	jFoo := labels.MustNewMatcher(labels.MatchEqual, "j", "foo")
+	jNotFoo := labels.MustNewMatcher(labels.MatchNotEqual, "j", "foo")
+
+	iStar := labels.MustNewMatcher(labels.MatchRegexp, "i", "^.*$")
+	iPlus := labels.MustNewMatcher(labels.MatchRegexp, "i", "^.+$")
+	i1Plus := labels.MustNewMatcher(labels.MatchRegexp, "i", "^1.+$")
+	iEmptyRe := labels.MustNewMatcher(labels.MatchRegexp, "i", "^$")
+	iNotEmpty := labels.MustNewMatcher(labels.MatchNotEqual, "i", "")
+	iNot2 := labels.MustNewMatcher(labels.MatchNotEqual, "n", "2"+postingsBenchSuffix)
+	iNot2Star := labels.MustNewMatcher(labels.MatchNotRegexp, "i", "^2.*$")
+
+	cases := []struct {
+		name     string
+		matchers []*labels.Matcher
+	}{
+		{`n="1"`, []*labels.Matcher{n1}},
+		{`n="1",j="foo"`, []*labels.Matcher{n1, jFoo}},
+		{`j="foo",n="1"`, []*labels.Matcher{jFoo, n1}},
+		{`n="1",j!="foo"`, []*labels.Matcher{n1, jNotFoo}},
+		{`i=~".*"`, []*labels.Matcher{iStar}},
+		{`i=~".+"`, []*labels.Matcher{iPlus}},
+		{`i=~""`, []*labels.Matcher{iEmptyRe}},
+		{`i!=""`, []*labels.Matcher{iNotEmpty}},
+		{`n="1",i=~".*",j="foo"`, []*labels.Matcher{n1, iStar, jFoo}},
+		{`n="1",i=~".*",i!="2",j="foo"`, []*labels.Matcher{n1, iStar, iNot2, jFoo}},
+		{`n="1",i!=""`, []*labels.Matcher{n1, iNotEmpty}},
+		{`n="1",i!="",j="foo"`, []*labels.Matcher{n1, iNotEmpty, jFoo}},
+		{`n="1",i=~".+",j="foo"`, []*labels.Matcher{n1, iPlus, jFoo}},
+		{`n="1",i=~"1.+",j="foo"`, []*labels.Matcher{n1, i1Plus, jFoo}},
+		{`n="1",i=~".+",i!="2",j="foo"`, []*labels.Matcher{n1, iPlus, iNot2, jFoo}},
+		{`n="1",i=~".+",i!~"2.*",j="foo"`, []*labels.Matcher{n1, iPlus, iNot2Star, jFoo}},
+	}
+
+	for _, c := range cases {
+		b.Run(c.name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				_, err := PostingsForMatchers(ir, c.matchers...)
+				testutil.Ok(b, err)
+			}
+		})
+	}
+}