Answer by Frank Heikens for Best way to implement non-mergeable view in PostgreSQL

I would start using JOIN's as the new standard, since 30 years ago, ANSI SQL-92.

And when you need data from t1 and t2, there is no need for joining t3: Use EXISTS to check for the condition.

To improve performance, you need EXPLAIN(ANALYZE, VERBOSE, BUFFERS, SETTINGS) to get the plan and the details about the execution. Just EXPLAIN tells you almost nothing, it's just a plan and you don't know if it's a good or bad one. You don't see the issues either.

And about the query above, without details it's not clear what the problem is. You want a specific order in the execution, but it's not clear why and if it would really solve the (unknown) problem.