Thanks all for the reminders about analyzing, and I apologize for wasting
everyone's time. The main table did indeed need to be analyzed (I had
truncated it and repopulated it with "insert ... select" but forgotten to
analyze). The other tables are very small temporary tables, and I assumed,
whether correctly or not, that analyzing would not be helpful for them.
All this is happening in the context of an algorithm in a PL/PGSQL function.
The three temporary tables are reused thousands of times. I wasn't sure if
it would be better to truncate them between uses to keep them small or just
allow them to grow. Unfortunately for the Tree of Knowledge, performance is
now more than adequate, so I may not do this experiment.
Thanks,
Kevin Murphy