apache
Error is reported when concurrently merging nodes/edges
Describe the bug When multiple clients perform merge edges concurrently, there is error reported, "sequence already exists", or "relation already exists". Here is my code:
I try to fix this issue in this PR: https://github.com/apache/age/pull/2178. But the issue still exists.
How are you accessing AGE (Command line, driver, etc.)?
- python driver
What data setup do we need to do?
What is the necessary configuration info needed?
- [e.g. Installed PostGIS]
What is the command that caused the error?
cq = f"""
--
| MATCH (source:{source_node_label} {{doc_id:'{doc_id}'}})
| MATCH (target:{target_node_label} {{doc_id:'{doc_id}'}})
| WITH source, target
| MERGE (source)-[r:DIRECTED]->(target)
| SET {set_properties}
| RETURN r
| """
| query = sql.SQL(
| f"SELECT * FROM cypher('{self.graph_name}', $$ {cq} $$) as (result agtype)"
| )
Error message is:
Key (relname, relnamespace)=(DIRECTED_id_seq, 42609) already exists.
Or
relation "DIRECTED" already exists
Expected behavior A clear and concise description of what you expected to happen.
Environment (please complete the following information):
- Version: [e.g. 0.4.0]
Additional context Add any other context about the problem here.
I think I have found the root cause. The "merge" operation creates table( or sequence) with the same name concurrently, but in PG the behavior must raise error. Like the below transaction sequence:
-- TX1
begin;
create table demo(id int); -- success
-- TX2
begin;
create table demo(id int); -- blocked
-- TX1
commit;
-- TX2
-- create table failed
Therefore, I think AGE doesn't support concurrent merge operation.