Correctly merge rows for identical series

If no chunking was requested by the user, the co-ordinating node buffers all
results in RAM before emitting a single result. However buffering was not
merging results for rows which had data for the same series. This change fixes this.

Fixes issue #3242.

cmd/influxd/run/server_test.go

@@ -3007,6 +3007,57 @@ func TestServer_Query_Fill(t *testing.T) {
 	}
 }
 
+func TestServer_Query_Chunk(t *testing.T) {
+	t.Parallel()
+	s := OpenServer(NewConfig(), "")
+	defer s.Close()
+
+	if err := s.CreateDatabaseAndRetentionPolicy("db0", newRetentionPolicyInfo("rp0", 1, 0)); err != nil {
+		t.Fatal(err)
+	}
+	if err := s.MetaStore.SetDefaultRetentionPolicy("db0", "rp0"); err != nil {
+		t.Fatal(err)
+	}
+
+	writes := make([]string, 10001) // 10,000 is the default chunking size, even when no chunking requested.
+	expectedValues := make([]string, len(writes))
+	for i := 0; i < len(writes); i++ {
+		writes[i] = fmt.Sprintf(`cpu value=%d %d`, i, time.Unix(0, int64(i)).UnixNano())
+		expectedValues[i] = fmt.Sprintf(`["%s",%d]`, time.Unix(0, int64(i)).UTC().Format(time.RFC3339Nano), i)
+	}
+	expected := fmt.Sprintf(`{"results":[{"series":[{"name":"cpu","columns":["time","value"],"values":[%s]}]}]}`, strings.Join(expectedValues, ","))
+
+	test := NewTest("db0", "rp0")
+	test.write = strings.Join(writes, "\n")
+
+	test.addQueries([]*Query{
+		&Query{
+			name:    "SELECT all values, no chunking",
+			command: `SELECT value FROM cpu`,
+			exp:     expected,
+			params:  url.Values{"db": []string{"db0"}},
+		},
+	}...)
+
+	for i, query := range test.queries {
+		if i == 0 {
+			if err := test.init(s); err != nil {
+				t.Fatalf("test init failed: %s", err)
+			}
+		}
+		if query.skip {
+			t.Logf("SKIP:: %s", query.name)
+			continue
+		}
+		if err := query.Execute(s); err != nil {
+			t.Error(query.Error(err))
+		} else if !query.success() {
+			t.Error(query.failureMessage())
+		}
+	}
+
+}
+
 func TestServer_Query_DropAndRecreateMeasurement(t *testing.T) {
 	t.Parallel()
 	s := OpenServer(NewConfig(), "")

influxql/result.go

@@ -31,6 +31,11 @@ type Row struct {
 	Err     error             `json:"err,omitempty"`
 }
 
+// SameSeries returns true if r contains values for the same series as o.
+func (r *Row) SameSeries(o *Row) bool {
+	return r.tagsHash() == o.tagsHash() && r.Name == o.Name
+}
+
 // tagsHash returns a hash of tag key/value pairs.
 func (r *Row) tagsHash() uint64 {
 	h := fnv.New64a()

services/httpd/handler.go

@@ -286,6 +286,21 @@ func (h *Handler) serveQuery(w http.ResponseWriter, r *http.Request, user *meta.
 			resp.Results = append(resp.Results, r)
 		} else if resp.Results[l-1].StatementID == r.StatementID {
 			cr := resp.Results[l-1]
+			lastSeries := cr.Series[len(cr.Series)-1]
+			rowsMerged := 0
+
+			for _, row := range r.Series {
+				if !lastSeries.SameSeries(row) {
+					// Next row is for a different series than last.
+					break
+				}
+				// Values are for the same series, so append them.
+				lastSeries.Values = append(lastSeries.Values, row.Values...)
+				rowsMerged++
+			}
+
+			// Append remaining rows as new rows.
+			r.Series = r.Series[rowsMerged:]
 			cr.Series = append(cr.Series, r.Series...)
 		} else {
 			resp.Results = append(resp.Results, r)