Create/alter policy and exclusive table lock

Hi hackers,

Right now changing policies (create/alter policy statements) requires 
exclusive lock of target table:

     /* Get id of table.  Also handles permissions checks. */
     table_id = RangeVarGetRelidExtended(stmt->table, AccessExclusiveLock,
                                         0,
                                         RangeVarCallbackForPolicy,
                                         (void *) stmt);

Unfortunately there are use cases where policies are changed quite 
frequently and this exclusive lock becomes a bottleneck.
I wonder why do we really need exclusive lock here?
Policies are stored in pg_policy table and we get  RowExclusiveLock on it.

May be I missed something, but why we can not rely on standard MVCC 
visibility rules for pg_policy table?
Until transaction executing CREATE/ALTER POLICY is committed, other 
transactions will not see its changes in pg_policy table and perform
RLS checks according to old policies. Once transaction is committed, 
everybody will switch to new policies.

I wonder if we it is possible to replace AccessExclusiveLock with 
AccessSharedLock in RangeVarGetRelidExtended in CreatePolicy and 
AlterPolicy?

-- 
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company