In expand_security_qual(), we were handling locking correctly when a
PlanRowMark existed, but not when we were working with the target
relation (which doesn't have any PlanRowMarks, but the subquery created
for the security barrier quals still needs to lock the rows under it).
Noted by Etsuro Fujita when working with the Postgres FDW, which wasn't
properly issuing a SELECT ... FOR UPDATE to the remote side under a
DELETE.
Back-patch to 9.4 where updatable security barrier views were
introduced.
Per discussion with Etsuro and Dean Rasheed.
This clause changes the behavior of SELECT locking clauses in the
presence of locked rows: instead of causing a process to block waiting
for the locks held by other processes (or raise an error, with NOWAIT),
SKIP LOCKED makes the new reader skip over such rows. While this is not
appropriate behavior for general purposes, there are some cases in which
it is useful, such as queue-like tables.
Catalog version bumped because this patch changes the representation of
stored rules.
Reviewed by Craig Ringer (based on a previous attempt at an
implementation by Simon Riggs, who also provided input on the syntax
used in the current patch), David Rowley, and Álvaro Herrera.
Author: Thomas Munro
This function created new Vars with varno different from varnoold, which
is a condition that should never prevail before setrefs.c does the final
variable-renumbering pass. The created Vars could not be seen as equal()
to normal Vars, which among other things broke equivalence-class processing
for them. The consequences of this were indeed visible in the regression
tests, in the form of failure to propagate constants as one would expect.
I stumbled across it while poking at bug #11457 --- after intentionally
disabling join equivalence processing, the security-barrier regression
tests started falling over with fun errors like "could not find pathkey
item to sort", because of failure to match the corrupted Vars to normal
ones.
In some cases, not all Vars were being correctly marked as having been
modified for updatable security barrier views, which resulted in invalid
plans (eg: when security barrier views were created over top of
inheiritance structures).
In passing, be sure to update both varattno and varonattno, as _equalVar
won't consider the Vars identical otherwise. This isn't known to cause
any issues with updatable security barrier views, but was noticed as
missing while working on RLS and makes sense to get fixed.
Back-patch to 9.4 where updatable security barrier views were
introduced.
Views which are marked as security_barrier must have their quals
applied before any user-defined quals are called, to prevent
user-defined functions from being able to see rows which the
security barrier view is intended to prevent them from seeing.
Remove the restriction on security barrier views being automatically
updatable by adding a new securityQuals list to the RTE structure
which keeps track of the quals from security barrier views at each
level, independently of the user-supplied quals. When RTEs are
later discovered which have securityQuals populated, they are turned
into subquery RTEs which are marked as security_barrier to prevent
any user-supplied quals being pushed down (modulo LEAKPROOF quals).
Dean Rasheed, reviewed by Craig Ringer, Simon Riggs, KaiGai Kohei
