pgsql-hackers
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Pgbench: remove synchronous prepare
- Jump to comment-1Dmitrii Bondar<d.bondar@postgrespro.ru>Jan 27, 2026, 3:35 AM UTCHi, Hackers!
I was testing a connection pooler with pgbench and pgbench froze. I checked the traffic and noticed that pgbench just blocks the execution while it is waiting the response to the prepare command.
To reproduce the problem, it is enough to run pgbouncer with the session pooling mode and use more clients than the pool size. With the pool size of 20:
pgbench -h localhost -p 6432 --client=21 --jobs=1 -S -T 1000 -P 1 postgres --protocol=prepared
Pgbench with the extended protocol flag does not have this issue because pgbench sends the whole parse/bind/execute/sync packet sequence at once and waits for the result asynchronously. I suggest implementing this behavior for the prepared protocol too.
I attached the pgbouncer configuration to reproduce the issue and the proposed fix. I prefer to add a new function to libpqfe instead of changing the existing behavior or adding a new state to pgbench. Although it is largely duplicated code, it looks to be as non-invasive as possible. Implementation and naming need to be discussed.
Tests for pgbench passed. I made small changes to the expected output.
Regards,
Dmitrii Bondar.