From 3a7ab3b8eb68faa43cf709e8677a2580afb5a906 Mon Sep 17 00:00:00 2001
From: Seebs <seebs@seebs.net>
Date: Fri, 17 Apr 2020 14:21:41 -0500
Subject: [PATCH] GroupBy should terminate even if the last result is empty

If you have two criteria, and the last result you generate is
empty, the nextAtIdx iterator for i==1 will try to continue
poking the i==0 iterator. That one produces a nil result, and
declares the entire group-by iterator done... But the nextAtIdx
call above it isn't checking that, and just loops forever.
This causes some queries to become stuck permanently, consuming
ridiculous amounts of resources almost entirely focused on
calling Intersect millions of times to get empty results.
---
 executor.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/executor.go b/executor.go
index d9622329d..3badd4906 100644
--- a/executor.go
+++ b/executor.go
@@ -4665,6 +4665,9 @@ func (gbi *groupByIterator) nextAtIdx(i int) {
 		}
 		if wrapped && i != 0 {
 			gbi.nextAtIdx(i - 1)
+			if gbi.done {
+				return
+			}
 		}
 		if i == 0 && gbi.filter != nil {
 			gbi.rows[i].row = nr.Intersect(gbi.filter)