[SOLVED] PostgreSQL Autocommit efficiency on SELECT queries

PostgreSQL Autocommit efficiency on SELECT queries

I am using Psycopg2 to issue many SELECT queries to my Postgres DB. These queries have a small size result and they are sent at a high frequency.

In order to avoid managing transactions myself (because I'm lazy), I have set autocommit = True in the session settings.

Edit: there is no long pause between queries, no data manipulation, and the cursor gets closed immediately after I stop making queries.

I would like to know: When issuing SELECT queries at a high frequency, is there any performance penalty of using autocommit?

Using Postgres 9.6 and Psycopg 2.7.7. And yes, I am using prepared statements.

Solution

Autocommit is the right thing because:

There is no performance penalty because a read-only transaction does not have to write to the transaction log (WAL).
No locks are held, like a_horse_with_no_name commented. Even a SELECT holds a n ACCESS SHARE lock on the table, which will block commands like TRUNCATE, DROP TABLE and vacuum truncation.
The driver doesn't have to send those extra BEGIN and COMMIT statements, which will cause unnecessary client-server round trips.