All,
I've been keeping an eye on tick as it failed a day-or-so ago and it looks to be related to RLS. Using a local
CLFAGS="-DCLOBBER_CACHE_ALWAYS-DRANDOMIZE_ALLOCATED_MEMORY" build, I was able to see the regression tests failing in
check_role_for_policy()due to a pretty clear reset of the memory used for the policies.
Looking through relcache.c, which I have to admit to not being as familiar with as some, the issue becomes rather
apparent(I believe)- RelationClearRelation() hasn't been set up to handle the RLS policies specially, as it does for
rulesand tupledesc. Fair enough, it's reasonably straight-forward to add an equalPolicies() and handle the policies
thesame way- but I'm left wondering if that's actually *safe* to do?
To be a bit more clear- why is it safe to change the contents if the equal() function returns 'false'? I'm guessing
theanswer is "locking"- whereby such a change would imply a lock was acquired on the relation by another backend, which
shouldn'tbe possible if we're currently working with it, but wanted to double-check that. I also wonder if we might be
betteroff with a way to identify that nothing has actually been changed due to the locks we hold and avoid rebuilding
therelation cache entry entirely..
Thanks!
Stephen
