fix: do not panic on cleaning up failed iterators

CHANGELOG.md

@@ -1,6 +1,10 @@
 v1.9.3 [unreleased]
+
+#### Bugfixes
+
 -	[#21592](https://github.com/influxdata/influxdb/pull/21592): fix: avoid rewriting fields.idx unnecessarily
 -	[#21659](https://github.com/influxdata/influxdb/pull/21659): fix: do not close connection twice in DigestWithOptions
+-	[#21666](https://github.com/influxdata/influxdb/pull/21666): fix: do not panic on cleaning up failed iterators
 
 v1.9.2 [unreleased]
 -	[#21631](https://github.com/influxdata/influxdb/pull/21631): fix: group by returns multiple results per group in some circumstances

query/iterator.go

@@ -43,11 +43,22 @@ func (a Iterators) Stats() IteratorStats {
 }
 
 // Close closes all iterators.
-func (a Iterators) Close() error {
+// We are seeing an occasional panic in this function
+// which looks like a nil reference from one
+// itr.Close() call, thus we check for nil elements
+// in the slice a.  This is often called as error
+// clean-up, so the state of the iterators may be
+// unhappy.
+func (a Iterators) Close() (err error) {
+	err = nil
 	for _, itr := range a {
-		itr.Close()
+		if itr != nil {
+			if e := itr.Close(); e != nil && err == nil {
+				err = e
+			}
+		}
 	}
-	return nil
+	return err
 }
 
 // filterNonNil returns a slice of iterators that removes all nil iterators.