From 57de42bb91cc0ec09b5045a9e940394f52eb9b09 Mon Sep 17 00:00:00 2001
From: Matt Jaffee <jaffee@umbel.com>
Date: Thu, 2 Mar 2017 16:27:45 -0600
Subject: [PATCH] fix empty queries crashing pilosa

---
 executor.go      |  8 +++++++-
 executor_test.go | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/executor.go b/executor.go
index f29fdfe9f..0ba1e7017 100644
--- a/executor.go
+++ b/executor.go
@@ -265,6 +265,9 @@ func (e *Executor) executeTopNSlice(ctx context.Context, db string, c *pql.Call,
 // executeDifferenceSlice executes a difference() call for a local slice.
 func (e *Executor) executeDifferenceSlice(ctx context.Context, db string, c *pql.Call, slice uint64) (*Bitmap, error) {
 	var other *Bitmap
+	if len(c.Children) == 0 {
+		return nil, fmt.Errorf("empty Difference query is currently not supported")
+	}
 	for i, input := range c.Children {
 		bm, err := e.executeBitmapCallSlice(ctx, db, input, slice)
 		if err != nil {
@@ -308,6 +311,9 @@ func (e *Executor) executeBitmapSlice(ctx context.Context, db string, c *pql.Cal
 // executeIntersectSlice executes a intersect() call for a local slice.
 func (e *Executor) executeIntersectSlice(ctx context.Context, db string, c *pql.Call, slice uint64) (*Bitmap, error) {
 	var other *Bitmap
+	if len(c.Children) == 0 {
+		return nil, fmt.Errorf("empty Intersect query is currently not supported")
+	}
 	for i, input := range c.Children {
 		bm, err := e.executeBitmapCallSlice(ctx, db, input, slice)
 		if err != nil {
@@ -382,7 +388,7 @@ func (e *Executor) executeRangeSlice(ctx context.Context, db string, c *pql.Call
 
 // executeUnionSlice executes a union() call for a local slice.
 func (e *Executor) executeUnionSlice(ctx context.Context, db string, c *pql.Call, slice uint64) (*Bitmap, error) {
-	var other *Bitmap
+	other := NewBitmap()
 	for i, input := range c.Children {
 		bm, err := e.executeBitmapCallSlice(ctx, db, input, slice)
 		if err != nil {
diff --git a/executor_test.go b/executor_test.go
index 7cc7af2eb..1ad1fbbbb 100644
--- a/executor_test.go
+++ b/executor_test.go
@@ -50,6 +50,18 @@ func TestExecutor_Execute_Difference(t *testing.T) {
 	}
 }
 
+// Ensure an empty difference query behaves properly.
+func TestExecutor_Execute_Empty_Difference(t *testing.T) {
+	idx := MustOpenIndex()
+	defer idx.Close()
+	idx.MustCreateFragmentIfNotExists("d", "general", 0).MustSetBits(10, 1)
+
+	e := NewExecutor(idx.Index, NewCluster(1))
+	if res, err := e.Execute(context.Background(), "d", MustParse(`Difference()`), nil, nil); err == nil {
+		t.Fatalf("Empty Difference query should give error, but got %v", res)
+	}
+}
+
 // Ensure an intersect query can be executed.
 func TestExecutor_Execute_Intersect(t *testing.T) {
 	idx := MustOpenIndex()
@@ -70,6 +82,17 @@ func TestExecutor_Execute_Intersect(t *testing.T) {
 	}
 }
 
+// Ensure an empty intersect query behaves properly.
+func TestExecutor_Execute_Empty_Intersect(t *testing.T) {
+	idx := MustOpenIndex()
+	defer idx.Close()
+
+	e := NewExecutor(idx.Index, NewCluster(1))
+	if res, err := e.Execute(context.Background(), "d", MustParse(`Intersect()`), nil, nil); err == nil {
+		t.Fatalf("Empty Intersect query should give error, but got %v", res)
+	}
+}
+
 // Ensure a union query can be executed.
 func TestExecutor_Execute_Union(t *testing.T) {
 	idx := MustOpenIndex()
@@ -89,6 +112,20 @@ func TestExecutor_Execute_Union(t *testing.T) {
 	}
 }
 
+// Ensure an empty union query behaves properly.
+func TestExecutor_Execute_Empty_Union(t *testing.T) {
+	idx := MustOpenIndex()
+	defer idx.Close()
+	idx.MustCreateFragmentIfNotExists("d", "general", 0).MustSetBits(10, 0)
+
+	e := NewExecutor(idx.Index, NewCluster(1))
+	if res, err := e.Execute(context.Background(), "d", MustParse(`Union()`), nil, nil); err != nil {
+		t.Fatal(err)
+	} else if bits := res[0].(*pilosa.Bitmap).Bits(); !reflect.DeepEqual(bits, []uint64{}) {
+		t.Fatalf("unexpected bits: %+v", bits)
+	}
+}
+
 // Ensure a count query can be executed.
 func TestExecutor_Execute_Count(t *testing.T) {
 	idx := MustOpenIndex()