Prevent deadlock when doing math on the result of a subquery

The `fill(none)` attribute got set on subqueries, but that can cause an
issue with certain subqueries just like it caused a deadlock on outer
queries.

CHANGELOG.md

@@ -58,6 +58,7 @@
 - [#8697](https://github.com/influxdata/influxdb/issues/8697): Drop Series Cause Write Fail/Write Timeouts/High Memory Usage
 - [#8741](https://github.com/influxdata/influxdb/issues/8741): Fix increased memory usage in cache and wal readers
 - [#8678](https://github.com/influxdata/influxdb/issues/8678): Ensure time and tag-based condition can be used with tsi1 index when deleting.
+- [#8848](https://github.com/influxdata/influxdb/issues/8848): Prevent deadlock when doing math on the result of a subquery.
 
 ## v1.3.4 [unreleased]
 

query/iterator.go

@@ -837,12 +837,15 @@ func newIteratorOptionsSubstatement(stmt *influxql.SelectStatement, opt Iterator
 	// Propagate the ordering from the parent query.
 	subOpt.Ascending = opt.Ascending
 
-	// If the inner query uses a null fill option, switch it to none so we
-	// don't hit an unnecessary penalty from the fill iterator. Null values
-	// will end up getting stripped by an outer query anyway so there's no
-	// point in having them here. We still need all other types of fill
-	// iterators because they can affect the result of the outer query.
-	if subOpt.Fill == influxql.NullFill {
+	// If the inner query uses a null fill option and is not a raw query,
+	// switch it to none so we don't hit an unnecessary penalty from the
+	// fill iterator. Null values will end up getting stripped by an outer
+	// query anyway so there's no point in having them here. We still need
+	// all other types of fill iterators because they can affect the result
+	// of the outer query. We also do not do this for raw queries because
+	// there is no fill iterator for them and fill(none) doesn't work with
+	// raw queries.
+	if !stmt.IsRawQuery && subOpt.Fill == influxql.NullFill {
 		subOpt.Fill = influxql.NoFill
 	}
 

tests/server_test.go

@@ -5459,6 +5459,52 @@ func TestServer_Query_SubqueryWithGroupBy(t *testing.T) {
 	}
 }
 
+func TestServer_Query_SubqueryMath(t *testing.T) {
+	t.Parallel()
+	s := OpenServer(NewConfig())
+	defer s.Close()
+
+	if err := s.CreateDatabaseAndRetentionPolicy("db0", newRetentionPolicySpec("rp0", 1, 0), true); err != nil {
+		t.Fatal(err)
+	}
+
+	writes := []string{
+		fmt.Sprintf("m0 f2=4,f3=2 %d", mustParseTime(time.RFC3339Nano, "2000-01-01T00:00:00Z").UnixNano()),
+		fmt.Sprintf("m0 f1=5,f3=8 %d", mustParseTime(time.RFC3339Nano, "2000-01-01T00:00:10Z").UnixNano()),
+		fmt.Sprintf("m0 f1=5,f2=3,f3=6 %d", mustParseTime(time.RFC3339Nano, "2000-01-01T00:00:20Z").UnixNano()),
+	}
+	test := NewTest("db0", "rp0")
+	test.writes = Writes{
+		&Write{data: strings.Join(writes, "\n")},
+	}
+
+	test.addQueries([]*Query{
+		&Query{
+			name:    "SumThreeValues",
+			params:  url.Values{"db": []string{"db0"}},
+			command: `SELECT sum FROM (SELECT f1 + f2 + f3 AS sum FROM m0)`,
+			exp:     `{"results":[{"statement_id":0,"series":[{"name":"m0","columns":["time","sum"],"values":[["2000-01-01T00:00:00Z",null],["2000-01-01T00:00:10Z",null],["2000-01-01T00:00:20Z",14]]}]}]}`,
+		},
+	}...)
+
+	if err := test.init(s); err != nil {
+		t.Fatalf("test init failed: %s", err)
+	}
+
+	for _, query := range test.queries {
+		t.Run(query.name, func(t *testing.T) {
+			if query.skip {
+				t.Skipf("SKIP:: %s", query.name)
+			}
+			if err := query.Execute(s); err != nil {
+				t.Error(query.Error(err))
+			} else if !query.success() {
+				t.Error(query.failureMessage())
+			}
+		})
+	}
+}
+
 func TestServer_Query_PercentileDerivative(t *testing.T) {
 	t.Parallel()
 	s := OpenServer(NewConfig())