Alastair McKinley <a.mckinley@xxxxxxxxxxxxxxxxxxxx> writes: > I have recently encountered a strange poor query plan choice after implementing RLS. > My table has a number of partial indexes on a jsonb column and the query went from low number of milliseconds to several seconds as the planner chose a different index. > Simply stated, in the jsonb column case, "using ( (select true) )" instead of "using (true)" produces a bad plan, illustrated below: If the planner isn't sure you have access to all rows in the table, that disables some of its ability to estimate where-clause selectivity. In particular it can't run "leaky" where-clauses against all values in the table's statistics entries to see how many pass, because a nefarious user could use that to glean info about what's in the table. Eyeing your test query, it looks like the issue is that jsonb "->" isn't leakproof, so that clause falls back to a default selectivity estimate, and you get a bad plan as a result. regards, tom lane
