Merge pull request #458 from RoaringBitmap/fix-457

Fix issue 457.

Author: lemire

roaring64/bsi64.go

@@ -97,6 +97,9 @@ func (b *BSI) SetBigValue(columnID uint64, value *big.Int) {
 	// If max/min values are set to zero then automatically determine bit array size
 	if b.MaxValue == 0 && b.MinValue == 0 {
 		minBits := value.BitLen() + 1
+		if minBits == 1 {
+			minBits = 2
+		}
 		for len(b.bA) < minBits {
 			b.bA = append(b.bA, Bitmap{})
 		}

roaring64/bsi64_test.go

@@ -112,6 +112,13 @@ func TestSetAndGetBigTimestamp(t *testing.T) {
 	assert.Equal(t, 67, bsi.BitCount())
 }
 
+// This tests a corner case where a zero value is set on an empty BSI.  The bit count should never be zero.
+func TestSetInitialValueZero(t *testing.T) {
+	bsi := NewDefaultBSI()
+	bsi.SetBigValue(1, big.NewInt(0))
+	assert.Equal(t, 1, bsi.BitCount())
+}
+
 func TestRangeBig(t *testing.T) {
 
 	bsi := NewDefaultBSI()
@@ -262,15 +269,11 @@ func TestNewBSI(t *testing.T) {
 	bsi = NewDefaultBSI()
 	assert.Equal(t, 0, bsi.BitCount())
 	bsi.SetValue(1, int64(0))
-	assert.Equal(t, 0, bsi.BitCount())
+	assert.Equal(t, 1, bsi.BitCount())
 	bsi.SetValue(1, int64(-1))
 	assert.Equal(t, 1, bsi.BitCount())
 }
 
-func TestStuff(t *testing.T) {
-
-}
-
 func TestGE(t *testing.T) {
 
 	bsi := setup()