From 3235d83c9b6debe7266248c2ec854af3d8783a8e Mon Sep 17 00:00:00 2001
From: Todd Gruben <tgruben@umbel.com>
Date: Wed, 23 Aug 2017 13:12:28 -0500
Subject: [PATCH] Xor support for PQL

---
 bitmap.go        | 27 +++++++++++++++++++++++++++
 executor.go      | 21 +++++++++++++++++++++
 executor_test.go | 19 +++++++++++++++++++
 3 files changed, 67 insertions(+)

diff --git a/bitmap.go b/bitmap.go
index ecdb4c076..eb8f7f799 100644
--- a/bitmap.go
+++ b/bitmap.go
@@ -97,6 +97,22 @@ func (b *Bitmap) Intersect(other *Bitmap) *Bitmap {
 	return &Bitmap{segments: segments}
 }
 
+// Xor returns the xor of b and other.
+func (b *Bitmap) Xor(other *Bitmap) *Bitmap {
+	var segments []BitmapSegment
+
+	itr := newMergeSegmentIterator(b.segments, other.segments)
+	for s0, s1 := itr.next(); s0 != nil || s1 != nil; s0, s1 = itr.next() {
+		// Ignore non-overlapping segments.
+		if s0 == nil || s1 == nil {
+			continue
+		}
+		segments = append(segments, *s0.Xor(s1))
+	}
+
+	return &Bitmap{segments: segments}
+}
+
 // Union returns the bitwise union of b and other.
 func (b *Bitmap) Union(other *Bitmap) *Bitmap {
 	var segments []BitmapSegment
@@ -342,6 +358,17 @@ func (s *BitmapSegment) Difference(other *BitmapSegment) *BitmapSegment {
 	}
 }
 
+// Xor returns the xor of s and other.
+func (s *BitmapSegment) Xor(other *BitmapSegment) *BitmapSegment {
+	data := s.data.Xor(&other.data)
+
+	return &BitmapSegment{
+		data:  *data,
+		slice: s.slice,
+		n:     data.Count(),
+	}
+}
+
 // SetBit sets the i-th bit of the bitmap.
 func (s *BitmapSegment) SetBit(i uint64) (changed bool) {
 	s.ensureWritable()
diff --git a/executor.go b/executor.go
index aa5b69034..24777a6f1 100644
--- a/executor.go
+++ b/executor.go
@@ -316,6 +316,8 @@ func (e *Executor) executeBitmapCallSlice(ctx context.Context, index string, c *
 		return e.executeRangeSlice(ctx, index, c, slice)
 	case "Union":
 		return e.executeUnionSlice(ctx, index, c, slice)
+	case "Xor":
+		return e.executeXorSlice(ctx, index, c, slice)
 	default:
 		return nil, fmt.Errorf("unknown call: %s", c.Name)
 	}
@@ -721,6 +723,25 @@ func (e *Executor) executeUnionSlice(ctx context.Context, index string, c *pql.C
 	return other, nil
 }
 
+// executeXorSlice executes a xor() call for a local slice.
+func (e *Executor) executeXorSlice(ctx context.Context, index string, c *pql.Call, slice uint64) (*Bitmap, error) {
+	other := NewBitmap()
+	for i, input := range c.Children {
+		bm, err := e.executeBitmapCallSlice(ctx, index, input, slice)
+		if err != nil {
+			return nil, err
+		}
+
+		if i == 0 {
+			other = bm
+		} else {
+			other = other.Xor(bm)
+		}
+	}
+	other.InvalidateCount()
+	return other, nil
+}
+
 // executeCount executes a count() call.
 func (e *Executor) executeCount(ctx context.Context, index string, c *pql.Call, slices []uint64, opt *ExecOptions) (uint64, error) {
 	if len(c.Children) == 0 {
diff --git a/executor_test.go b/executor_test.go
index 265293aef..269747efb 100644
--- a/executor_test.go
+++ b/executor_test.go
@@ -187,6 +187,25 @@ func TestExecutor_Execute_Empty_Union(t *testing.T) {
 	}
 }
 
+// Ensure a xor query can be executed.
+func TestExecutor_Execute_Xor(t *testing.T) {
+	hldr := test.MustOpenHolder()
+	defer hldr.Close()
+	hldr.MustCreateFragmentIfNotExists("i", "general", pilosa.ViewStandard, 0).MustSetBits(10, 0)
+	hldr.MustCreateFragmentIfNotExists("i", "general", pilosa.ViewStandard, 1).MustSetBits(10, SliceWidth+1)
+	hldr.MustCreateFragmentIfNotExists("i", "general", pilosa.ViewStandard, 1).MustSetBits(10, SliceWidth+2)
+
+	hldr.MustCreateFragmentIfNotExists("i", "general", pilosa.ViewStandard, 0).MustSetBits(11, 2)
+	hldr.MustCreateFragmentIfNotExists("i", "general", pilosa.ViewStandard, 1).MustSetBits(11, SliceWidth+2)
+
+	e := test.NewExecutor(hldr.Holder, test.NewCluster(1))
+	if res, err := e.Execute(context.Background(), "i", test.MustParse(`Xor(Bitmap(rowID=10), Bitmap(rowID=11))`), nil, nil); err != nil {
+		t.Fatal(err)
+	} else if bits := res[0].(*pilosa.Bitmap).Bits(); !reflect.DeepEqual(bits, []uint64{0, 2, SliceWidth + 1}) {
+		t.Fatalf("unexpected bits: %+v", bits)
+	}
+}
+
 // Ensure a count query can be executed.
 func TestExecutor_Execute_Count(t *testing.T) {
 	hldr := test.MustOpenHolder()