Morocco, Iraq, Choibalsan, Pakistan, Syria, Cuba, Argentina/San_Luis).

require SELECT privilege as well, since you normally need to read existing
column values within such commands.  This behavior is according to spec,
but we'd never documented it before.  Per gripe from Volkan Yazici.

current transaction has any open references to the target relation or index
(implying it has an active query using the relation).  Also back-patch the
8.2 fix that prohibits TRUNCATE and CLUSTER when there are pending
AFTER-trigger events.  Per suggestion from Heikki.

called before, not after, calling the assign_hook if any.  This is because
push_old_value might fail (due to palloc out-of-memory), and in that case
there would be no stack entry to tell transaction abort to undo the GUC
assignment.  Of course the actual assignment to the GUC variable hasn't
happened yet --- but the assign_hook might have altered subsidiary state.
Without a stack entry we won't call it again to make it undo such actions.
So this is necessary to make the world safe for assign_hooks with side
effects.  Per a discussion a couple weeks ago with Magnus.

Back-patch to 8.0.  7.x did not have the problem because it did not have
allocatable stacks of GUC values.

cases.  Recent buildfarm experience shows that it is sometimes possible
to execute several SQL commands in less time than the granularity of
Windows' not-very-high-resolution gettimeofday(), leading to a failure
because the tests expect the value of now() to change and it doesn't.
Also, it was recognized some time ago that the same area of the tests
could fail if local midnight passes between the insertion and the checking
of the values for 'yesterday', 'tomorrow', etc.  Clean all this up per
ideas from myself and Greg Stark.

There remains a window for failure if the transaction block is entered
exactly at local midnight (so that 'now' and 'today' have the same value),
but that seems low-probability enough to live with.

Since the point of this change is mostly to eliminate buildfarm noise,
back-patch to all versions we are still actively testing.