fix: Handling empty values

CHANGELOG.md

@@ -1,7 +1,10 @@
 ## 1.2.0
 ## Breaking Change
  - [#107](https://github.com/influxdata/influxdb-client-go/pull/100) Renamed `InfluxDBClient` interface to `Client`, so the full name `influxdb2.Client` suits better to Go naming conventions
-
+
+## Bug fixes 
+1. [#110](https://github.com/influxdata/influxdb-client-go/issues/110) Allowing empty (nil) values
+
 ## 1.1.0 [2020-04-24]
 ### Features
 1. [#100](https://github.com/influxdata/influxdb-client-go/pull/100)  HTTP request timeout made configurable

query.go

@@ -346,6 +346,9 @@ func stringTernary(a, b string) string {
 
 // toValues converts s into type by t
 func toValue(s, t, name string) (interface{}, error) {
+	if s == "" {
+		return nil, nil
+	}
 	switch t {
 	case stringDatatype:
 		return s, nil

query_test.go

@@ -648,6 +648,39 @@ func TestDifferentNumberOfColumns(t *testing.T) {
 	assert.Equal(t, "parsing error, row has different number of columns than table: 11 vs 10", queryResult.Err().Error())
 }
 
+func TestEmptyValue(t *testing.T) {
+	csvTable := `#datatype,string,long,dateTime:RFC3339,dateTime:RFC3339,dateTime:RFC3339,double,string,string,string,string
+#group,false,false,true,true,false,false,true,true,true,true
+#default,_result,,,,,,,,,
+,result,table,_start,_stop,_time,_value,_field,_measurement,a,b
+,,0,2020-02-17T22:19:49.747562847Z,2020-02-18T22:19:49.747562847Z,2020-02-18T10:34:08.135814545Z,,f,test,1,adsfasdf
+,,0,2020-02-17T22:19:49.747562847Z,2020-02-18T22:19:49.747562847Z,2020-02-18T22:08:44.850214724Z,6.6,f,test,,adsfasdf
+,,0,2020-02-17T22:19:49.747562847Z,2020-02-18T22:19:49.747562847Z,2020-02-18T22:11:32.225467895Z,1122.45,f,test,3,
+`
+
+	reader := strings.NewReader(csvTable)
+	csvReader := csv.NewReader(reader)
+	csvReader.FieldsPerRecord = -1
+	queryResult := &QueryTableResult{Closer: ioutil.NopCloser(reader), csvReader: csvReader}
+
+	require.True(t, queryResult.Next(), queryResult.Err())
+	require.Nil(t, queryResult.Err())
+
+	require.NotNil(t, queryResult.Record())
+	assert.Nil(t, queryResult.Record().Value())
+
+	require.True(t, queryResult.Next(), queryResult.Err())
+	require.NotNil(t, queryResult.Record())
+	assert.Nil(t, queryResult.Record().ValueByKey("a"))
+
+	require.True(t, queryResult.Next(), queryResult.Err())
+	require.NotNil(t, queryResult.Record())
+	assert.Nil(t, queryResult.Record().ValueByKey("b"))
+
+	require.False(t, queryResult.Next())
+	require.Nil(t, queryResult.Err())
+}
+
 func TestFluxError(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		time.Sleep(100 * time.Millisecond)

table.go

@@ -155,7 +155,7 @@ func (r *FluxRecord) Time() time.Time {
 	return r.ValueByKey("_time").(time.Time)
 }
 
-// Value returns the actual field value
+// Value returns the default _value column value or nil if not present
 func (r *FluxRecord) Value() interface{} {
 	return r.ValueByKey("_value")
 }
@@ -175,7 +175,7 @@ func (r *FluxRecord) Values() map[string]interface{} {
 	return r.values
 }
 
-// ValueByKey returns value for given column key for the record
+// ValueByKey returns value for given column key for the record or nil of result has no value the column key
 func (r *FluxRecord) ValueByKey(key string) interface{} {
 	return r.values[key]
 }