fix

src/graph/optimizer/rule/OptimizeLeftJoinPredicateRule.h

@@ -10,6 +10,23 @@
 namespace nebula {
 namespace opt {
 
+/*
+Before:
+   BiLeftJoin({id(v)}, id(v))
+       /    \
+    ...    Project
+                 \
+                AppendVertices(v)
+                           \
+                          Traverse(e)
+
+After:
+   BiLeftJoin({id(v)}, none_direct_dst(e))
+       /    \
+    ...    Project
+                 \
+               Traverse(e)
+*/
 class OptimizeLeftJoinPredicateRule final : public OptRule {
  public:
   const Pattern &pattern() const override;

tests/tck/features/optimizer/OptimizeLeftJoinPredicateRule.feature

@@ -0,0 +1,64 @@
+# Copyright (c) 2021 vesoft inc. All rights reserved.
+#
+# This source code is licensed under Apache 2.0 License.
+Feature: Optimize left join predicate
+
+  Background:
+    Given a graph with space named "nba"
+
+  Scenario: optimize left join predicate
+    When profiling query:
+      """
+      MATCH (person:player)-[:like*1..2]-(friend:player)-[:serve]->(friendTeam:team)
+      WHERE id(person) == "Tony Parker" AND id(friend) != "Tony Parker"
+      WITH DISTINCT friend, friendTeam
+      OPTIONAL MATCH (friend)<-[:like]-(friend2:player)<-[:like]-(friendTeam)
+      WITH friendTeam, count(friend2) AS numFriends
+      RETURN
+        id(friendTeam) AS teamId,
+        friendTeam.team.name AS teamName,
+        numFriends
+        ORDER BY numFriends DESC
+        LIMIT 20
+      """
+    Then the result should be, in any order, with relax comparison:
+      | teamId          | teamName        | numFriends |
+      | "Clippers"      | "Clippers"      | 0          |
+      | "Bulls"         | "Bulls"         | 0          |
+      | "Spurs"         | "Spurs"         | 0          |
+      | "Thunders"      | "Thunders"      | 0          |
+      | "Hornets"       | "Hornets"       | 0          |
+      | "Warriors"      | "Warriors"      | 0          |
+      | "Hawks"         | "Hawks"         | 0          |
+      | "Kings"         | "Kings"         | 0          |
+      | "Magic"         | "Magic"         | 0          |
+      | "Trail Blazers" | "Trail Blazers" | 0          |
+      | "Lakers"        | "Lakers"        | 0          |
+      | "Grizzlies"     | "Grizzlies"     | 0          |
+      | "Suns"          | "Suns"          | 0          |
+      | "Rockets"       | "Rockets"       | 0          |
+      | "Cavaliers"     | "Cavaliers"     | 0          |
+      | "Raptors"       | "Raptors"       | 0          |
+      | "Celtics"       | "Celtics"       | 0          |
+      | "76ers"         | "76ers"         | 0          |
+      | "Heat"          | "Heat"          | 0          |
+      | "Jazz"          | "Jazz"          | 0          |
+    And the execution plan should be:
+      | id | name           | dependencies | profiling data | operator info |
+      | 21 | TopN           | 18           |                |               |
+      | 18 | Project        | 17           |                |               |
+      | 17 | Aggregate      | 16           |                |               |
+      | 16 | BiLeftJoin     | 10,15        |                |               |
+      | 10 | Dedup          | 28           |                |               |
+      | 28 | Project        | 22           |                |               |
+      | 22 | Filter         | 26           |                |               |
+      | 26 | AppendVertices | 25           |                |               |
+      | 25 | Traverse       | 24           |                |               |
+      | 24 | Traverse       | 2            |                |               |
+      | 2  | Dedup          | 1            |                |               |
+      | 1  | PassThrough    | 3            |                |               |
+      | 3  | Start          |              |                |               |
+      | 15 | Project        | 14           |                |               |
+      | 14 | Traverse       | 12           |                |               |
+      | 12 | Traverse       | 11           |                |               |
+      | 11 | Argument       |              |                |               |