added Numeric as an option as target datatype for bigint (GoogleCloudPlatform#1187)

Co-authored-by: Sandeep Mishra <iamsandeep@google.com>

Author: sm745052

sources/mysql/toddl.go

@@ -137,6 +137,8 @@ func toSpannerTypeInternal(srcType schema.Type, spType string) (ddl.Type, []inte
 		switch spType {
 		case ddl.String:
 			return ddl.Type{Name: ddl.String, Len: ddl.MaxLength}, []internal.SchemaIssue{internal.Widened}
+		case ddl.Numeric:
+			return ddl.Type{Name: ddl.Numeric}, []internal.SchemaIssue{internal.Widened}
 		default:
 			return ddl.Type{Name: ddl.Int64}, nil
 		}

sources/mysql/toddl_test.go

@@ -67,6 +67,10 @@ func TestToSpannerTypeInternal(t *testing.T) {
 	if errCheck == nil {
 		t.Errorf("Error in bigint to string conversion")
 	}
+	_, errCheck = toSpannerTypeInternal(schema.Type{"bigint", []int64{1, 2, 3}, []int64{1, 2, 3}}, "NUMERIC")
+	if errCheck == nil {
+		t.Errorf("Error in bigint to numeric conversion")
+	}
 	_, errCheck = toSpannerTypeInternal(schema.Type{"int", []int64{1, 2, 3}, []int64{1, 2, 3}}, "STRING")
 	if errCheck == nil {
 		t.Errorf("Error in int to string conversion")