fix: Pass index type for Scalar indexes (#696)

Related to #694 #695

---------

Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>

entity/index_scalar.go

@@ -7,7 +7,11 @@ type indexScalar struct {
 }
 
 func (i *indexScalar) Params() map[string]string {
-	return map[string]string{}
+	result := make(map[string]string)
+	if i.baseIndex.it != "" {
+		result[tIndexType] = string(i.baseIndex.it)
+	}
+	return result
 }
 
 func NewScalarIndex() Index {

entity/index_scalar_test.go

@@ -10,8 +10,16 @@ func TestScalarIndex(t *testing.T) {
 	oldScalarIdx := NewScalarIndex()
 
 	assert.EqualValues(t, "", oldScalarIdx.IndexType(), "use AUTO index when index type not provided")
+	_, has := oldScalarIdx.Params()[tIndexType]
+	assert.False(t, has)
 
 	idxWithType := NewScalarIndexWithType(Sorted)
 
 	assert.EqualValues(t, Sorted, idxWithType.IndexType())
+	assert.EqualValues(t, Sorted, idxWithType.Params()[tIndexType])
+
+	idxWithType = NewScalarIndexWithType(Trie)
+
+	assert.EqualValues(t, Trie, idxWithType.IndexType())
+	assert.EqualValues(t, Trie, idxWithType.Params()[tIndexType])
 }