[PERFORM] Row-level security performance

Hi,

I see in the v10 release notes (2017-10-05) that there's been a change to "Improve performance of queries affected by
row-levelsecurity restrictions". I am using RLS in a Postgres 9.5 database and am seeing some very bad performance when
joiningtables. Upgrading this DB to v10 shows a huge performance increase in some cases where RLS has proven to be an
issue,but not all. 

I see here (https://www.postgresql.org/message-id/14730.1508278004%40sss.pgh.pa.us), that Tom Lane (author of the
commitfor the aforementioned release note) remarked on 2017-10-17: "I would *not* recommend RLS if you can equally well
stickthe equivalent conditions into your queries.  There is way too much risk of taking a serious performance hit due
toa bad plan." 

What's the current advice, and future plans for row-level security performance optimisations?
Though things have improved in v10, is there likely to always be that risk of a bad plan arising?

Regards,
Jason Borg.


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