Someone was just complaining over in the sql list about the poor
performance of
select name,description from descriptions
where name in (select name
from descriptions
where description like '%Bankverbindung%');
Since the inner query is uncorrelated with the outer, there's really
no need to execute it more than once, but currently it's re-executed
each time through the outer plan.
I wonder whether it wouldn't be a good idea to force a Materialize
node to be added to the top of an uncorrelated subplan? Then at
least the re-executions would be pretty cheap...
regards, tom lane