Improve our mechanism for controlling the Linux out-of-memory killer.

Arrange for postmaster child processes to respond to two environment
variables, PG_OOM_ADJUST_FILE and PG_OOM_ADJUST_VALUE, to determine whether
they reset their OOM score adjustments and if so to what.  This is superior
to the previous design involving #ifdef's in several ways.  The behavior is
now available in a default build, and both ends of the adjustment --- the
original adjustment of the postmaster's level and the subsequent
readjustment by child processes --- can now be controlled in one place,
namely the postmaster launch script.  So it's no longer necessary for the
launch script to act on faith that the server was compiled with the
appropriate options.  In addition, if someone wants to use an OOM score
other than zero for the child processes, that doesn't take a recompile
anymore; and we no longer have to cater separately to the two different
historical kernel APIs for this adjustment.

Gurjeet Singh, somewhat revised by me
Don't allow data_directory to be set in postgresql.auto.conf by ALTER SYSTEM.

data_directory could be set both in postgresql.conf and postgresql.auto.conf so far.
This could cause some problematic situations like circular definition. To avoid such
situations, this commit forbids a user to set data_directory in postgresql.auto.conf.

Backpatch this to 9.4 where ALTER SYSTEM command was introduced.

Amit Kapila, reviewed by Abhijit Menon-Sen, with minor adjustments by me.
Fix calculation of PREDICATELOCK_MANAGER_LWLOCK_OFFSET.

Commit ea9df812d8502fff74e7bc37d61bdc7d66d77a7f failed to include
NUM_BUFFER_PARTITIONS in this offset, resulting in a bad offset.
Ultimately this threw off NUM_FIXED_LWLOCKS which is based on
earlier offsets, leading to memory allocation problems.  It seems
likely to have also caused increased LWLOCK contention when
serializable transactions were used, because lightweight locks used
for that overlapped others.

Reported by Amit Kapila with analysis and fix.
Backpatch to 9.4, where the bug was introduced.
Document SQL functions' behavior of parsing the whole function at once.

Haribabu Kommi, somewhat rewritten by me
Let installcheck-world pass against a server requiring a password.

Give passwords to each user created in support of an ECPG connection
test case.  Use SET SESSION AUTHORIZATION, not a fresh connection, to
reduce privileges during a dblink test case.

To test against such a server, both the "make installcheck-world"
environment and the postmaster environment must provide the default
user's password; $PGPASSFILE is the principal way to do so.  (The
postmaster environment needs it for dblink and postgres_fdw tests.)
Fix contrib/pg_upgrade/test.sh for $PWD containing spaces.

Most of the necessary quoting was in place; this catches the exceptions.
Avoid leaking memory while evaluating arguments for a table function.

ExecMakeTableFunctionResult evaluated the arguments for a function-in-FROM
in the query-lifespan memory context.  This is insignificant in simple
cases where the function relation is scanned only once; but if the function
is in a sub-SELECT or is on the inside of a nested loop, any memory
consumed during argument evaluation can add up quickly.  (The potential for
trouble here had been foreseen long ago, per existing comments; but we'd
not previously seen a complaint from the field about it.)  To fix, create
an additional temporary context just for this purpose.

Per an example from MauMau.  Back-patch to all active branches.
Don't allow to disable backend assertions via the debug_assertions GUC.

The existance of the assert_enabled variable (backing the
debug_assertions GUC) reduced the amount of knowledge some static code
checkers (like coverity and various compilers) could infer from the
existance of the assertion. That could have been solved by optionally
removing the assertion_enabled variable from the Assert() et al macros
at compile time when some special macro is defined, but the resulting
complication doesn't seem to be worth the gain from having
debug_assertions. Recompiling is fast enough.

The debug_assertions GUC is still available, but readonly, as it's
useful when diagnosing problems. The commandline/client startup option
-A, which previously also allowed to enable/disable assertions, has
been removed as it doesn't serve a purpose anymore.

While at it, reduce code duplication in bufmgr.c and localbuf.c
assertions checking for spurious buffer pins. That code had to be
reindented anyway to cope with the assert_enabled removal.
Do all-visible handling in lazy_vacuum_page() outside its critical section.

Since fdf9e21196a lazy_vacuum_page() rechecks the all-visible status
of pages in the second pass over the heap. It does so inside a
critical section, but both visibilitymap_test() and
heap_page_is_all_visible() perform operations that should not happen
inside one. The former potentially performs IO and both potentially do
memory allocations.

To fix, simply move all the all-visible handling outside the critical
section. Doing so means that the PD_ALL_VISIBLE on the page won't be
included in the full page image of the HEAP2_CLEAN record anymore. But
that's fine, the flag will be set by the HEAP2_VISIBLE logged later.

Backpatch to 9.3 where the problem was introduced. The bug only came
to light due to the assertion added in 4a170ee9 and isn't likely to
cause problems in production scenarios. The worst outcome is a
avoidable PANIC restart.

This also gets rid of the difference in the order of operations
between master and standby mentioned in 2a8e1ac5.

Per reports from David Leverton and Keith Fiske in bug #10533.
Clean up data conversion short-lived memory context.

dblink uses a short-lived data conversion memory context. However it
was not deleted when no longer needed, leading to a noticeable memory
leak under some circumstances. Plug the hole, along with minor
refactoring. Backpatch to 9.2 where the leak was introduced.

Report and initial patch by MauMau. Reviewed/modified slightly by
Tom Lane and me.
Add Asserts to verify that catalog cache keys are unique and not null.

The catcache code is effectively assuming this already, so let's insist
that the catalog and index are actually declared that way.

Having done that, the comments in indexing.h about non-unique indexes
not being used for catcaches are completely redundant not just mostly so;
and we didn't have such a comment for every such index anyway.  So let's
get rid of them.

Per discussion of whether we should identify primary keys for catalogs.
We might or might not take that further step, but this change in itself
will allow quicker detection of misdeclared catcaches, so it seems worth
doing in any case.
Fix documentation template for CREATE TRIGGER.

By using curly braces, the template had specified that one of
"NOT DEFERRABLE", "INITIALLY IMMEDIATE", or "INITIALLY DEFERRED"
was required on any CREATE TRIGGER statement, which is not
accurate.  Change to square brackets makes that optional.

Backpatch to 9.1, where the error was introduced.
9.4 release notes:  adjust some entry wording

Backpatch to 9.4
doc:  adjust JSONB GIN index description

Backpatch through 9.4
Fix bug in WAL_DEBUG.

The record header was not copied correctly to the buffer that was passed
to the rm_desc function. Broken by my rm_desc signature refactoring patch.
Add missing closing parenthesis into max_replication_slots doc.
Fix typo in replication slot function doc.
Improve tab-completion of DROP and ALTER ENABLE/DISABLE on triggers and rules.

At "DROP RULE/TRIGGER triggername ON ...", tab-complete tables that have
a rule/trigger with that name.

At "ALTER TABLE tablename ENABLE/DISABLE TRIGGER/RULE ...", tab-complete to
rules/triggers on that table. Previously, we would tab-complete to all
rules or triggers, not just those that are on that table.

Also, filter out internal RI triggers from the list. You can't DROP them,
and enabling/disabling them is such a rare (and dangerous) operation that
it seems better to hide them.

Andreas Karlsson, reviewed by Ian Barwick.
Check for interrupts during tuple-insertion loops.

Normally, this won't matter too much; but if I/O is really slow, for
example because the system is overloaded, we might write many pages
before checking for interrupts.  A single toast insertion might
write up to 1GB of data, and a multi-insert could write hundreds
of tuples (and their corresponding TOAST data).
Don't allow foreign tables with OIDs.

The syntax doesn't let you specify "WITH OIDS" for foreign tables, but it
was still possible with default_with_oids=true. But the rest of the system,
including pg_dump, isn't prepared to handle foreign tables with OIDs
properly.

Backpatch down to 9.1, where foreign tables were introduced. It's possible
that there are databases out there that already have foreign tables with
OIDs. There isn't much we can do about that, but at least we can prevent
them from being created in the future.

Patch by Etsuro Fujita, reviewed by Hadi Moshayedi.