Inconsistent evaluation of pattern predicate in `WHERE`: `()--()` differs from `NOT((()--()) XOR true)`

[zihaozeng0021]

Configuration

Nebula Version: 2025.10.28-nightly

Operating System: WSL2 – Ubuntu 24.04.1 LTS

Installation Method: Docker

---

Steps to reproduce

1. Start Nebula via Docker

docker exec -it nebula-docker-compose-console-1 sh

2. Connect with nebula-console:

nebula-console -u root -p nebula -addr graphd -port 9669

3. Run the following query:

Create a test space

CREATE SPACE IF NOT EXISTS test(partition_num=1, replica_factor=1, vid_type=FIXED_STRING(8));

Select the space

use test

Setup

CREATE TAG IF NOT EXISTS L(n string);
CREATE EDGE IF NOT EXISTS E();

INSERT VERTEX L(n) VALUES "a":("a"), "b":("b"), "c":("c");
INSERT EDGE E() VALUES "a"->"b":();

Sanity-check that an edge exists:

(root@nebula) [test]> MATCH ()-[e:E]->() RETURN e;
+---------------------+
| e                   |
+---------------------+
| [:E "a"->"b" @0 {}] |
+---------------------+
Got 1 rows (time spent 8.558ms/9.200294ms)

Thu, 25 Dec 2025 06:37:04 UTC

Run the buggy queries:

(root@nebula) [test]> MATCH (n:L) WHERE ()--() RETURN n;
+---+
| n |
+---+
+---+
Empty set (time spent 5.52ms/5.904034ms)

Thu, 25 Dec 2025 06:37:11 UTC

(root@nebula) [test]> MATCH (n:L) WHERE NOT((()--()) XOR true) RETURN n;
+------------------+
| n                |
+------------------+
| ("a" :L{n: "a"}) |
| ("b" :L{n: "b"}) |
| ("c" :L{n: "c"}) |
+------------------+
Got 3 rows (time spent 5.994ms/6.312413ms)

Thu, 25 Dec 2025 06:37:16 UTC

---

Expected behaviour

These two queries should return the same result set because their WHERE clauses are logically equivalent:

• WHERE ()--()
• WHERE NOT((()--()) XOR true)

Actual behaviour

Their outputs are different with each other

• MATCH (n:L) WHERE ()--() RETURN n; → Empty set
• MATCH (n:L) WHERE NOT((()--()) XOR true) RETURN n; → 3 rows (a, b, c)