Add postings intersection

postings.go

@@ -52,6 +52,13 @@ func (e errPostings) Seek(uint32) bool { return false }
 func (e errPostings) Value() uint32    { return 0 }
 func (e errPostings) Err() error       { return e.err }
 
+func expandPostings(p Postings) (res []uint32, err error) {
+	for p.Next() {
+		res = append(res, p.Value())
+	}
+	return res, p.Err()
+}
+
 // Intersect returns a new postings list over the intersection of the
 // input postings.
 func Intersect(its ...Postings) Postings {
@@ -61,29 +68,61 @@ func Intersect(its ...Postings) Postings {
 	a := its[0]
 
 	for _, b := range its[1:] {
-		a = &intersectPostings{a: a, b: b}
+		a = newIntersectPostings(a, b)
 	}
 	return a
 }
 
 type intersectPostings struct {
 	a, b     Postings
+	av, bc   uint32
+	aok, bok bool
+	cur      uint32
+}
+
+func newIntersectPostings(a, b Postings) *intersectPostings {
+	it := &intersectPostings{a: a, b: b}
+	it.aok = it.a.Next()
+	it.bok = it.b.Next()
+
+	return it
 }
 
 func (it *intersectPostings) Value() uint32 {
-	return 0
+	return it.cur
 }
 
 func (it *intersectPostings) Next() bool {
+	for {
+		if !it.aok || !it.bok {
 			return false
+		}
+		av, bv := it.a.Value(), it.b.Value()
+
+		if av < bv {
+			it.aok = it.a.Seek(bv)
+		} else if bv < av {
+			it.bok = it.b.Seek(av)
+		} else {
+			it.cur = av
+			it.aok = it.a.Next()
+			it.bok = it.b.Next()
+			return true
+		}
+	}
 }
 
 func (it *intersectPostings) Seek(id uint32) bool {
-	return false
+	it.aok = it.a.Seek(id)
+	it.bok = it.b.Seek(id)
+	return it.Next()
 }
 
 func (it *intersectPostings) Err() error {
-	return nil
+	if it.a.Err() != nil {
+		return it.a.Err()
+	}
+	return it.b.Err()
 }
 
 // Merge returns a new iterator over the union of the input iterators.

postings_test.go

@@ -0,0 +1,140 @@
+package tsdb
+
+import (
+	"reflect"
+	"testing"
+)
+
+type mockPostings struct {
+	next  func() bool
+	seek  func(uint32) bool
+	value func() uint32
+	err   func() error
+}
+
+func (m *mockPostings) Next() bool         { return m.next() }
+func (m *mockPostings) Seek(v uint32) bool { return m.seek(v) }
+func (m *mockPostings) Value() uint32      { return m.value() }
+func (m *mockPostings) Err() error         { return m.err() }
+
+func newListPostings(list []uint32) *mockPostings {
+	i := -1
+	return &mockPostings{
+		next: func() bool {
+			i++
+			return i < len(list)
+		},
+		seek: func(v uint32) bool {
+			for ; i < len(list); i++ {
+				if list[i] >= v {
+					return true
+				}
+			}
+			return false
+		},
+		value: func() uint32 {
+			return list[i]
+		},
+		err: func() error { return nil },
+	}
+}
+func TestIntersectIterator(t *testing.T) {
+	var cases = []struct {
+		a, b []uint32
+		res  []uint32
+	}{
+		{
+			a:   []uint32{1, 2, 3, 4, 5},
+			b:   []uint32{6, 7, 8, 9, 10},
+			res: nil,
+		},
+		{
+			a:   []uint32{1, 2, 3, 4, 5},
+			b:   []uint32{4, 5, 6, 7, 8},
+			res: []uint32{4, 5},
+		},
+		{
+			a:   []uint32{1, 2, 3, 4, 9, 10},
+			b:   []uint32{1, 4, 5, 6, 7, 8, 10, 11},
+			res: []uint32{1, 4, 10},
+		}, {
+			a:   []uint32{1},
+			b:   []uint32{0, 1},
+			res: []uint32{1},
+		},
+	}
+
+	for i, c := range cases {
+		a := newListPostings(c.a)
+		b := newListPostings(c.b)
+
+		res, err := expandPostings(Intersect(a, b))
+		if err != nil {
+			t.Fatalf("%d: Unexpected error: %s", i, err)
+		}
+		if !reflect.DeepEqual(res, c.res) {
+			t.Fatalf("%d: Expected %v but got %v", i, c.res, res)
+		}
+	}
+}
+
+func TestMultiIntersect(t *testing.T) {
+	var cases = []struct {
+		a, b, c []uint32
+		res     []uint32
+	}{
+		{
+			a:   []uint32{1, 2, 3, 4, 5, 6, 1000, 1001},
+			b:   []uint32{2, 4, 5, 6, 7, 8, 999, 1001},
+			c:   []uint32{1, 2, 5, 6, 7, 8, 1001, 1200},
+			res: []uint32{2, 5, 6, 1001},
+		},
+	}
+
+	for _, c := range cases {
+		pa := newListPostings(c.a)
+		pb := newListPostings(c.b)
+		pc := newListPostings(c.c)
+
+		res, err := expandPostings(Intersect(pa, pb, pc))
+		if err != nil {
+			t.Fatalf("Unexpected error: %s", err)
+		}
+		if !reflect.DeepEqual(res, c.res) {
+			t.Fatalf("Expected %v but got %v", c.res, res)
+		}
+	}
+}
+
+func BenchmarkIntersect(t *testing.B) {
+	var a, b, c, d []uint32
+
+	for i := 0; i < 10000000; i += 2 {
+		a = append(a, uint32(i))
+	}
+	for i := 5000000; i < 5000100; i += 4 {
+		b = append(b, uint32(i))
+	}
+	for i := 5090000; i < 5090600; i += 4 {
+		b = append(b, uint32(i))
+	}
+	for i := 4990000; i < 5100000; i++ {
+		c = append(c, uint32(i))
+	}
+	for i := 4000000; i < 6000000; i++ {
+		d = append(d, uint32(i))
+	}
+
+	i1 := newListPostings(a)
+	i2 := newListPostings(b)
+	i3 := newListPostings(c)
+	i4 := newListPostings(d)
+
+	t.ResetTimer()
+
+	for i := 0; i < t.N; i++ {
+		if _, err := expandPostings(Intersect(i1, i2, i3, i4)); err != nil {
+			t.Fatal(err)
+		}
+	}
+}

querier.go

@@ -252,13 +252,6 @@ func (q *blockQuerier) selectSingle(m labels.Matcher) Postings {
 	return Intersect(rit...)
 }
 
-func expandPostings(p Postings) (res []uint32, err error) {
-	for p.Next() {
-		res = append(res, p.Value())
-	}
-	return res, p.Err()
-}
-
 func (q *blockQuerier) LabelValues(name string) ([]string, error) {
 	tpls, err := q.index.LabelValues(name)
 	if err != nil {