hkjiang26 opened a new issue, #2506:
URL: https://github.com/apache/age/issues/2506
## Bug description
Writing a Cypher `CREATE` that creates a relationship whose start/end vertex
is `NULL` — a value produced by an `OPTIONAL MATCH` that matched nothing —
crashes the PostgreSQL backend with a segmentation fault. The backend process
is terminated (`signal 11: Segmentation fault`) and the connection is dropped.
Instead of raising a normal error for a NULL endpoint, AGE 1.8.0 dereferences
the NULL vertex and crashes.
## Access method
- Command line via `psql`, inside the official Docker container
`apache/age:1.8.0`
## Data setup
One graph with a single node. No edges.
```pgsql
CREATE EXTENSION IF NOT EXISTS age;
LOAD 'age';
SET search_path = ag_catalog, "$user", public;
SELECT create_graph('graph_test');
SELECT * FROM cypher('graph_test', $$ CREATE (a:Node {name: 'A'}) $$) AS (c0
agtype);
```
## Configuration
- None beyond the stock AGE extension. No additional modules (no PostGIS,
etc.), default `search_path` handling as shown above.
## Command that triggers the crash
```pgsql
SELECT * FROM cypher('graph_test', $$ MATCH (a:Node {name: 'A'}) OPTIONAL
MATCH (a)-[:LINK_TO]->(c) CREATE (a)-[:LINK_TO]->(c) $$) AS (c0 agtype);
```
The `OPTIONAL MATCH` does not match (no `LINK_TO` edge exists), so `c` is
bound to `NULL`; the subsequent `CREATE (a)-[:LINK_TO]->(c)` then tries to
create a relationship whose endpoint is `NULL`.
```
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
```
The server log shows the backend being killed:
```
LOG: client backend (PID NNN) was terminated by signal 11: Segmentation
fault
LOG: terminating any other active server processes
LOG: all server processes terminated; reinitializing
```
## Expected behavior
`OPTIONAL MATCH` implements a left join: when the pattern does not match,
its variables are bound to `NULL`. The query is legal Cypher and should either
execute normally, or raise a normal Cypher error (e.g., "endpoint is null") —
it must not crash the backend process.
## Environment
- Version: 1.8.0 (official `apache/age:1.8.0` Docker image)
- PostgreSQL: 18.1 (Debian 18.1-1.pgdg13+2), x86_64
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