0001-Add-integration-test-to-trap-left-lateral-join-bug.patch

From c515297e3003ad2471df788f241a487d5b77ac40 Mon Sep 17 00:00:00 2001
From: Tom Taylor <tom@tomtaylor.co.uk>
Date: Fri, 2 Oct 2020 10:05:55 +0100
Subject: [PATCH] Add integration test to trap left lateral join bug

---
 integration_test/cases/joins.exs | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/integration_test/cases/joins.exs b/integration_test/cases/joins.exs
index d7d1e5e5..377f2d23 100644
--- a/integration_test/cases/joins.exs
+++ b/integration_test/cases/joins.exs
@@ -152,6 +152,30 @@ defmodule Ecto.Integration.JoinsTest do
     assert p2.permalink.id == plid1
   end
 
+  @tag :lateral_left_join
+  test "lateral left joins with missing entries" do
+    %Post{id: pid1} = TestRepo.insert!(%Post{title: "1"})
+    %Post{id: pid2} = TestRepo.insert!(%Post{title: "2"})
+
+    %Permalink{id: plid1} = TestRepo.insert!(%Permalink{url: "1", post_id: pid2})
+
+    %User{id: uid1} = TestRepo.insert!(%User{})
+
+    TestRepo.insert!(%Comment{text: "1", post_id: pid1, author_id: uid1})
+    TestRepo.insert!(%Comment{text: "2", post_id: nil, author_id: uid1})
+
+    comment_sq = from(c in Comment, where: parent_as(:posts).id == c.post_id)
+
+    query =
+      Post
+      |> from(as: :posts)
+      |> join(:left_lateral, [p], subquery(comment_sq))
+      |> join(:left, [p, c], u in User, on: c.author_id == u.id)
+      |> select([p, c, u], {p, c, u})
+
+    assert [{p1, c1, u1}, {p2, nil, nil}] = TestRepo.all(query)
+  end
+
   ## Associations joins
 
   test "has_many association join" do
-- 
2.28.0