PostgreSQL: How to Efficiently Retrieve Row Versions with `RETURNING` Clause and Handle Conflicts
I'm dealing with After trying multiple solutions online, I still can't figure this out. I'm working on a PostgreSQL 14 application that needs to insert new rows into a table while keeping track of row versions to handle simultaneous updates. I've implemented a function that inserts a row and returns the inserted row along with its version using the `RETURNING` clause. However, when two transactions attempt to insert the same data concurrently, I get a `deadlock detected` behavior. Here’s the relevant code snippet for the insert operation: ```sql CREATE TABLE items ( id SERIAL PRIMARY KEY, name TEXT NOT NULL, version INT DEFAULT 1 ); CREATE OR REPLACE FUNCTION insert_item(item_name TEXT) RETURNS RECORD AS $$ BEGIN INSERT INTO items (name) VALUES (item_name) ON CONFLICT (name) DO UPDATE SET version = items.version + 1 RETURNING *; END; $$ LANGUAGE plpgsql; ``` I’m calling this function from a Python application using `psycopg2`, and here’s how I’m executing the SQL: ```python import psycopg2 def insert_item(conn, name): with conn.cursor() as cursor: cursor.execute("SELECT insert_item(%s);", (name,)) return cursor.fetchone() ``` While this works well in most cases, I ran into issues when two processes try to insert the same item simultaneously. The conflicting rows seem to create a deadlock because both transactions are trying to update the same row at the same time. I've tried adding a retry mechanism to catch the `deadlock detected` behavior, but it seems inefficient since it causes delays in processing. Is there a better way to handle row versioning and prevent deadlocks in this scenario? Also, should I consider adding explicit locking, and if so, how would that affect performance? My development environment is macOS. I'd really appreciate any guidance on this. Could someone point me to the right documentation?