Re: Summary and Plan for Hot Standby

On Thu, 2009-11-19 at 10:13 +0200, Heikki Linnakangas wrote:

> At backend start, we normally take
> RowExclusiveLock on the database in postinit.c, but you had to modify
> to acquire AccessShareLock instead in standby mode.

The consensus from earlier discussion was that allowing users to grab
RowExclusiveLock during read only transactions was not a problem, since
it allowed PREPARE. So there seems no need to prevent it in other
places.

So I suggest removing most of the changes in postinit.c, and changing
the lock restrictions in lock.c to be

+    if (RecoveryInProgress() &&
+        (locktag->locktag_type == LOCKTAG_OBJECT ||
+         locktag->locktag_type == LOCKTAG_RELATION ) &&
+        lockmode > RowExclusiveLock)
then ERROR

lockcmds.c would also be changed to allow LOCK TABLE of up to
RowExclusiveLock.

-- Simon Riggs           www.2ndQuadrant.com