The original coding here was very confusing, because it named the
two servers it set up "master" and "slave" even though it swapped
their replication roles multiple times.  At any given point in the
script it was very unobvious whether "$node_master" actually referred
to the server named "master" or the other one.  Instead, pick arbitrary
names for the two servers --- I used "london" and "paris" --- and
distinguish those permanent names from the nonce references $cur_master
and $cur_slave.  Add logging to help distinguish which is which at
any given point.  Also, use distinct data and transaction names to
make all the prepared transactions easily distinguishable in the
postmaster logs.  (There was one place where we intentionally tested
that the server could cope with re-use of a transaction name, but
it seems like one place is sufficient for that purpose.)

Also, add checks at the end to make sure that all the transactions
that were supposed to be committed did survive.

Discussion: https://postgr.es/m/28238.1499010855@sss.pgh.pa.us

Add an optional "expected" argument to override the default assumption
that we're waiting for the query to return "t".  This allows replacing
a handwritten polling loop in recovery/t/007_sync_rep.pl with use of
poll_query_until(); AFAICS that's the only remaining ad-hoc polling
loop in our TAP tests.

Change poll_query_until() to probe ten times per second not once per
second.  Like some similar changes I've been making recently, the
one-second interval seems to be rooted in ancient traditions rather
than the actual likely wait duration on modern machines.  I'd consider
reducing it further if there were a convenient way to spawn just one
psql for the whole loop rather than one per probe attempt.

Discussion: https://postgr.es/m/12486.1498938782@sss.pgh.pa.us

Update the documentation a bit to include that logical replication as
well as other and third-party replication clients can participate in
synchronous replication.

The simple calculations done to estimate the size of the output buffers
for ucnv_fromUChars() and ucnv_toUChars() could overflow int32_t for
large strings.  To avoid that, go the long way and run the function
first without an output buffer to get the correct output buffer size
requirement.

Several callers of PostgresNode::poll_query_until() neglected to check
for failure; I do not think that's optional.  Also, rewrite one place
that had reinvented poll_query_until() for no very good reason.

The regression tests contain numerous cases where we do some activity on a
master server and then wait till the slave has ack'd flushing its copy of
that transaction.  Because WAL flush on the slave is asynchronous to the
logicalrep worker process, the worker cannot send such a feedback message
during the LogicalRepApplyLoop iteration where it processes the last data
from the master.  In the previous coding, the feedback message would come
out only when the loop's WaitLatchOrSocket call returned WL_TIMEOUT.  That
requires one full second of delay (NAPTIME_PER_CYCLE); and to add insult
to injury, it could take more than that if the WaitLatchOrSocket was
interrupted a few times by latch-setting events.

In reality we can expect the slave's walwriter process to have flushed the
WAL data after, more or less, WalWriterDelay (typically 200ms).  Hence,
if there are unacked transactions pending, make the wait delay only that
long rather than the full NAPTIME_PER_CYCLE.  Also, move one of the
send_feedback() calls into the loop main line, so that we'll check for the
need to send feedback even if we were woken by a latch event and not either
socket data or timeout.

It's not clear how much this matters for production purposes, but
it's definitely helpful for testing.

Discussion: https://postgr.es/m/30864.1498861103@sss.pgh.pa.us

When waiting for a logical replication worker process to start or stop,
we have to busy-wait until we see it add or remove itself from the
LogicalRepWorker slot in shared memory.  Those loops were using a
one-second delay between checks, but on any reasonably modern machine, it
doesn't take more than a couple of msec for a worker to spawn or shut down.
Reduce the loop delays to 10ms to avoid wasting quite so much time in the
related regression tests.

In principle, a better solution would be to fix things so that the waiting
process can be awakened via its latch at the right time.  But that seems
considerably more invasive, which is undesirable for a post-beta fix.
Worker start/stop performance likely isn't of huge interest anyway for
production purposes, so we might not ever get around to it.

In passing, rearrange the second wait loop in logicalrep_worker_stop()
so that the lock is held at the top of the loop, thus saving one lock
acquisition/release per call, and making it look more like the other loop.

Discussion: https://postgr.es/m/30864.1498861103@sss.pgh.pa.us

The bug would previously prevent the update of any column in a table
with identity columns, rather than just the actual identity column.

Reported-by: zam6ak@gmail.com
Bug: #14718

In WAL receiver and WAL server, some accesses to their corresponding
shared memory control structs were done without holding any kind of
lock, which could lead to inconsistent and possibly insecure results.

In walsender, fix by clarifying the locking rules and following them
correctly, as documented in the new comment in walsender_private.h;
namely that some members can be read in walsender itself without a lock,
because the only writes occur in the same process.  The rest of the
struct requires spinlock for accesses, as usual.

In walreceiver, fix by always holding spinlock while accessing the
struct.

While there is potentially a problem in all branches, it is minor in
stable ones.  This only became a real problem in pg10 because of quorum
commit in synchronous replication (commit 3901fd70), and a potential
security problem in walreceiver because a superuser() check was removed
by default monitoring roles (commit 25fff407).  Thus, no backpatch.

In passing, clean up some leftover braces which were used to create
unconditional blocks.  Once upon a time these were used for
volatile-izing accesses to those shmem structs, which is no longer
required.  Many other occurrences of this pattern remain.

Author: Michaël Paquier
Reported-by: Michaël Paquier
Reviewed-by: Masahiko Sawada, Kyotaro Horiguchi, Thomas Munro,
	Robert Haas
Discussion: https://postgr.es/m/CAB7nPqTWYqtzD=LN_oDaf9r-hAjUEPAy0B9yRkhcsLdRN8fzrw@mail.gmail.com

('foo') is not a Python tuple: it is a string wrapped in parentheses.  A
valid 1-element Python tuple is ('foo',).

Author: Daniele Varrazzo <daniele.varrazzo@gmail.com>

Author: Masahiko Sawada <sawada.mshk@gmail.com>

When a sync worker is waiting for the associated apply worker to notice
that it's in SYNCWAIT state, wait_for_worker_state_change() would just
patiently wait for that to happen.  This generally required waiting for
the 1-second timeout in LogicalRepApplyLoop to elapse.  Kicking the worker
via its latch makes things significantly snappier.

While at it, fix race conditions that could potentially result in crashes:
we can *not* call logicalrep_worker_wakeup_ptr() once we've released the
LogicalRepWorkerLock, because worker->proc might've been reset to NULL
after we do that (indeed, there's no really solid reason to believe that
the LogicalRepWorker slot even belongs to the same worker anymore).
In logicalrep_worker_wakeup(), we can just move the wakeup inside the
lock scope.  In process_syncing_tables_for_apply(), a bit more code
rearrangement is needed.

Also improve some nearby comments.

Author: Albe Laurenz <laurenz.albe@wien.gv.at>

Author: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>

Author: Thomas Munro <thomas.munro@enterprisedb.com>

Author: Michael Paquier <michael.paquier@gmail.com>

Oversight in commit 78c8c814; noted while nosing around the
walreceiver startup/shutdown code.

It's possible for WalSndWaitForWal to be asked to wait for WAL that doesn't
exist yet.  That's fine, in fact it's the normal situation if we're caught
up; but when the client requests shutdown we should not keep waiting.
The previous coding could wait indefinitely if the source server was idle.

In passing, improve the rather weak comments in this area, and slightly
rearrange some related code for better readability.

Back-patch to 9.4 where this code was introduced.

Discussion: https://postgr.es/m/14154.1498781234@sss.pgh.pa.us

ICU does not support "collate" and "ctype" being different, so the
collctype catalog column is ignored.  But for catalog neatness, ensure
that they are the same.

Masahiko Sawada

Discussion: http://postgr.es/m/CAD21AoA0jjXXhqK6Ym3jZNoUdVhXFyTkWTTTsVSr1vPuKcjsjA@mail.gmail.com

This command used to compute the collencoding entry like when a
completely new collation is created.  But for example when copying the
"C" collation, this would then result in a collation that has a
collencoding entry for the current database encoding rather than -1,
thus not making an exact copy.  This has probably no practical impact,
but making this change keeps the catalog contents neat.
Reported-by: Tom Lane <tgl@sss.pgh.pa.us>

The point of this loop is to insert 1000 rows into the test table
and consume 1000 XIDs.  I can't see any good reason why it's useful
to launch 1000 psqls and 1000 backend processes to accomplish that.
Pushing the looping into a plpgsql DO block shaves about 10 seconds
off the runtime of the src/test/recovery TAP tests on my machine;
that's over 10% of the runtime of that test suite.

It is, in fact, sufficiently more efficient that we now demonstrably
need wait_slot_xmins() afterwards, or the slaves' xmins may not have
moved yet.

Per buildfarm.

Traditionally, "pg_ctl start -w" has waited for the server to become
ready to accept connections by attempting a connection once per second.
That has the major problem that connection issues (for instance, a
kernel packet filter blocking traffic) can't be reliably told apart
from server startup issues, and the minor problem that if server startup
isn't quick, we accumulate "the database system is starting up" spam
in the server log.  We've hacked around many of the possible connection
issues, but it resulted in ugly and complicated code in pg_ctl.c.

In commit c61559ec, I changed the probe rate to every tenth of a second.
That prompted Jeff Janes to complain that the log-spam problem had become
much worse.  In the ensuing discussion, Andres Freund pointed out that
we could dispense with connection attempts altogether if the postmaster
were changed to report its status in postmaster.pid, which "pg_ctl start"
already relies on being able to read.  This patch implements that, teaching
postmaster.c to report a status string into the pidfile at the same
state-change points already identified as being of interest for systemd
status reporting (cf commit 7d17e683).  pg_ctl no longer needs to link
with libpq at all; all its functions now depend on reading server files.

In support of this, teach AddToDataDirLockFile() to allow addition of
postmaster.pid lines in not-necessarily-sequential order.  This is needed
on Windows where the SHMEM_KEY line will never be written at all.  We still
have the restriction that we don't want to truncate the pidfile; document
the reasons for that a bit better.

Also, fix the pg_ctl TAP tests so they'll notice if "start -w" mode
is broken --- before, they'd just wait out the sixty seconds until
the loop gives up, and then report success anyway.  (Yes, I found that
out the hard way.)

While at it, arrange for pg_ctl to not need to #include miscadmin.h;
as a rather low-level backend header, requiring that to be compilable
client-side is pretty dubious.  This requires moving the #define's
associated with the pidfile into a new header file, and moving
PG_BACKEND_VERSIONSTR someplace else.  For lack of a clearly better
"someplace else", I put it into port.h, beside the declaration of
find_other_exec(), since most users of that macro are passing the value to
find_other_exec().  (initdb still depends on miscadmin.h, but at least
pg_ctl and pg_upgrade no longer do.)

In passing, fix main.c so that PG_BACKEND_VERSIONSTR actually defines the
output of "postgres -V", which remarkably it had never done before.

Discussion: https://postgr.es/m/CAMkU=1xJW8e+CTotojOMBd-yzUvD0e_JZu2xHo=MnuZ4__m7Pg@mail.gmail.com

We now disallow having triggers with both transition tables and ON
INSERT OR UPDATE (which was a PG extension to the spec anyway),
because in this case it's not at all clear how the transition tables
should work for an INSERT ... ON CONFLICT query.  Separate ON INSERT
and ON UPDATE triggers with transition tables are allowed, and the
transition tables for these reflect only the inserted and only the
updated tuples respectively.

Patch by Thomas Munro

Discussion: https://postgr.es/m/CAEepm%3D11KHQ0JmETJQihSvhZB5mUZL2xrqHeXbCeLhDiqQ39%3Dw%40mail.gmail.com

The original coding didn't handle this case properly; each separate
DML substatement needs its own set of transitions.

Patch by Thomas Munro

Discussion: https://postgr.es/m/CAL9smLCDQ%3D2o024rBgtD4WihzX8B3C6u_oSQ2K3%2BR5grJrV0bg%40mail.gmail.com

We disallow row-level triggers with transition tables on child tables.
Transition tables for triggers on the parent table contain only those
columns present in the parent.  (We can't mix tuple formats in a
single transition table.)

Patch by Thomas Munro

Discussion: https://postgr.es/m/CA%2BTgmoZzTBBAsEUh4MazAN7ga%3D8SsMC-Knp-6cetts9yNZUCcg%40mail.gmail.com

Buildfarm evidence shows that TCP_KEEPALIVE_THRESHOLD doesn't exist
after all on Solaris < 11.  This means we need to take positive action to
prevent the TCP_KEEPALIVE code path from being taken on that platform.
I've chosen to limit it with "&& defined(__darwin__)", since it's unclear
that anyone else would follow Apple's precedent of spelling the symbol
that way.

Also, follow a suggestion from Michael Paquier of eliminating code
duplication by defining a couple of intermediate symbols for the
socket option.

In passing, make some effort to reduce the number of translatable messages
by replacing "setsockopt(foo) failed" with "setsockopt(%s) failed", etc,
throughout the affected files.  And update relevant documentation so
that it doesn't claim to provide an exhaustive list of the possible
socket option names.

Like the previous commit (f0256c77), back-patch to all supported branches.

Discussion: https://postgr.es/m/20170627163757.25161.528@wrigleys.postgresql.org

Commit 330b84d8 didn't contemplate the case where the public schema
has been dropped and introduced a query which fails when there is no
public schema into pg_dump (when used with -c).

Adjust the query used by pg_dump to handle the case where the public
schema doesn't exist and add tests to check that such a case no longer
fails.

Back-patch the specific fix to 9.6, as the prior commit was.

Adding tests for this case involved adding support to the pg_dump
TAP tests to work with multiple databases, which, while not a large
change, is a bit much to back-patch, so that's only done in master.

Addresses bug #14650
Discussion: https://www.postgresql.org/message-id/20170512181801.1795.47483%40wrigleys.postgresql.org

Turns out that the socket option for this is named TCP_KEEPALIVE_THRESHOLD,
at least according to the tcp(7P) man page for Solaris 11.  (But since that
text refers to "SunOS", it's likely pretty ancient.)  It appears that the
symbol TCP_KEEPALIVE does get defined on that platform, but it doesn't
seem to represent a valid protocol-level socket option.  This leads to
bleats in the postmaster log, and no tcp_keepalives_idle functionality.

Per bug #14720 from Andrey Lizenko, as well as an earlier report from
Dhiraj Chawla that nobody had followed up on.  The issue's been there
since we added the TCP_KEEPALIVE code path in commit 5acd417c, so
back-patch to all supported branches.

Discussion: https://postgr.es/m/20170627163757.25161.528@wrigleys.postgresql.org

check_agg_arguments_walker threw an error upon seeing a SRF or window
function, but that is too aggressive: if the function is within a
sub-select then it's perfectly fine.  I broke the SRF case in commit
0436f6bd by copying the logic for window functions ... but that was
broken too, and had been since commit eaccfded.

Repair both cases in HEAD, and the window function case back to 9.3.
9.2 gets this right.

By default, wal_retrieve_retry_interval is five seconds, which is far
more than is needed in any of our TAP tests, leaving the test cases
just twiddling their thumbs for significant stretches.  Moreover,
because it's so large, we get basically no testing of the retry-before-
master-is-ready code path.  Hence, make PostgresNode::init set up
wal_retrieve_retry_interval = '500ms' as part of its customization of
test clusters' postgresql.conf.  This shaves quite a few seconds off
the runtime of the recovery TAP tests.

Back-patch into 9.6.  We have wal_retrieve_retry_interval in 9.5,
but the test infrastructure isn't there.

Discussion: https://postgr.es/m/31624.1498500416@sss.pgh.pa.us

When a walreceiver dies, the startup process will notice that and send
a PMSIGNAL_START_WALRECEIVER signal to the postmaster, asking for a new
walreceiver to be launched.  There's a race condition, which at least
in HEAD is very easy to hit, whereby the postmaster might see that
signal before it processes the SIGCHLD from the walreceiver process.
In that situation, sigusr1_handler() just dropped the start request
on the floor, reasoning that it must be redundant.  Eventually, after
10 seconds (WALRCV_STARTUP_TIMEOUT), the startup process would make a
fresh request --- but that's a long time if the connection could have
been re-established almost immediately.

Fix it by setting a state flag inside the postmaster that we won't
clear until we do launch a walreceiver.  In cases where that results
in an extra walreceiver launch, it's up to the walreceiver to realize
it's unwanted and go away --- but we have, and need, that logic anyway
for the opposite race case.

I came across this through investigating unexpected delays in the
src/test/recovery TAP tests: it manifests there in test cases where
a master server is stopped and restarted while leaving streaming
slaves active.

This logic has been broken all along, so back-patch to all supported
branches.

Discussion: https://postgr.es/m/21344.1498494720@sss.pgh.pa.us

The stats collector disregards inquiry messages that bear a cutoff_time
before when it last wrote the relevant stats file.  That's fine, but at
startup when it reads the "permanent" stats files, it absorbed their
timestamps as if they were the times at which the corresponding temporary
stats files had been written.  In reality, of course, there's no data
out there at all.  This led to disregarding inquiry messages soon after
startup if the postmaster had been shut down and restarted within less
than PGSTAT_STAT_INTERVAL; which is a pretty common scenario, both for
testing and in the field.  Requesting backends would hang for 10 seconds
and then report failure to read statistics, unless they got bailed out
by some other backend coming along and making a newer request within
that interval.

I came across this through investigating unexpected delays in the
src/test/recovery TAP tests: it manifests there because the autovacuum
launcher hangs for 10 seconds when it can't get statistics at startup,
thus preventing a second shutdown from occurring promptly.  We might
want to do some things in the autovac code to make it less prone to
getting stuck that way, but this change is a good bug fix regardless.

In passing, also fix pgstat_read_statsfiles() to ensure that it
re-zeroes its global stats variables if they are corrupted by a
short read from the stats file.  (Other reads in that function
go into temp variables, so that the issue doesn't arise.)

This has been broken since we created the separation between permanent
and temporary stats files in 8.4, so back-patch to all supported branches.

Discussion: https://postgr.es/m/16860.1498442626@sss.pgh.pa.us

pg_ctl has traditionally waited one second between probes for whether
the start or stop request has completed.  That behavior was embodied
in the original shell script written in 1999 (commit 5b912b08) and
I doubt anyone's questioned it since.  Nowadays, machines are a lot
faster, and the shell script is long since replaced by C code, so it's
fair to reconsider how long we ought to wait.

This patch adjusts the coding so that the wait time can be any even
divisor of 1 second, and sets the actual probe rate to 10 per second.
That's based on experimentation with the src/test/recovery TAP tests,
which include a lot of postmaster starts and stops.  This patch alone
reduces the (non-parallelized) runtime of those tests from ~4m30s to
~3m5s on my machine.  Increasing the probe rate further doesn't help
much, so this seems like a good number.

In the real world this probably won't have much impact, since people
don't start/stop production postmasters often, and the shutdown checkpoint
usually takes nontrivial time too.  But it makes development work and
testing noticeably snappier, and that's good enough reason for me.

Also, by reducing the dead time in postmaster restart sequences, this
change has made it easier to reproduce some bugs that have been lurking
for awhile.  Patches for those will follow.

Discussion: https://postgr.es/m/18444.1498428798@sss.pgh.pa.us

Remove hard-wired sleep(2) delays in 001_stream_rep.pl in favor of using
poll_query_until to check for the desired state to appear.  In addition,
add such a wait before the last test in the script, as it's possible
to demonstrate failures there after upcoming improvements in pg_ctl.

(We might end up adding polling before each of the get_slot_xmins calls in
this script, but I feel no great need to do that until shown necessary.)

In passing, clarify the description strings for some of the test cases.

Michael Paquier and Craig Ringer, pursuant to a complaint from me

Discussion: https://postgr.es/m/8962.1498425057@sss.pgh.pa.us

This arises in practice if the partition only admits NULL values.

Jeevan Ladhe

Discussion: https://postgr.es/m/CAOgcT0OChrN--uuqH6wG6Z8+nxnCWJ+2Q-uhnK4KOANdRRxuAw@mail.gmail.com

Fix its header comment, which described the old behavior of the <N>
phrase distance operator; we missed updating that in commit 028350f6.
Also, reset errno before strtol() call, to defend against the possibility
that it was already ERANGE at entry.  (The lack of complaints says that
it generally isn't, but this is at least a latent bug.)  Very minor
stylistic improvements as well.

Victor Drobny noted the obsolete comment, I noted the errno issue.
Back-patch to 9.6 where this code was added, just in case the errno
issue is a live bug in some cases.

Discussion: https://postgr.es/m/2b5382fdff9b1f79d5eb2c99c4d2cbe2@postgrespro.ru