Reformat various places in which pgindent will make a mess, and
fix a few small violations of coding style that I happened to notice
while perusing the diffs from a pgindent dry run.

There is one actual bug fix here: the need-to-enlarge-the-buffer code
path in icu_convert_case was obviously broken.  Perhaps it's unreachable
in our usage?  Or maybe this is just sadly undertested.

Commit 827d6f97 contained the same misunderstanding of hash_create's API
as commit 090010f2.  As in 5d00b764, remove the unnecessary layer of
memory context.  (This bug is less significant than the other one, since
the extra context would be under a relatively short-lived context, but
it's still a bug.)

This reverts commit 4a03f935.

Since commit 4e37b3e1, buildfarm member frogmouth has been failing
occasionally with symptoms indicating that some expected stats data is
getting dropped.  The reason that that commit changed the behavior seems
probably to be that more data is getting shoved at the collector in a short
span of time.  In current sources, the stats test's first session sends
about 9KB of data while exiting, which is probably the same as what was
sent just before wait_for_stats() in the previous test design.  But now,
the test's second session is starting up concurrently, and it sends another
2KB (presumably reflecting its initial catalog accesses).  Since frogmouth
is running on Windows XP, which reputedly has a default socket receive
buffer size of only 8KB, it is not very surprising if this has put us over
the threshold where the receive buffer can overflow and drop messages.

The same mechanism could very easily explain the intermittent stats test
failures we've been seeing for years, since background processes such
as the bgwriter will sometimes send data concurrently with all this, and
could thus cause occasional buffer overflows.

Hence, insert some code into pgstat_init() to increase the stats socket's
receive buffer size to 100KB if it's less than that.  (On failure, emit a
LOG message, but keep going.)  Modern systems seem to have default sizes
in the range of 100KB-250KB, but older platforms don't.  I couldn't find
any platforms that wouldn't accept 100KB, so in theory this won't cause
any portability problems.

If this is successful at reducing the buildfarm failure rate in HEAD,
we should back-patch it, because it's certain that similar buffer overflows
happen in the field on platforms with small buffer sizes.  Going forward,
there might be an argument for trying to increase the buffer size even
more, but let's take a baby step first.

Discussion: https://postgr.es/m/22173.1494788088@sss.pgh.pa.us

Thomas Munro, reviewed by Amit Langote

Discussion: http://postgr.es/m/CAEepm=15Jss-yhFApuKzxcoCuFnb8TR8iQiWMjG=CLYPx48QLw@mail.gmail.com

Paul Jungwirth, reviewed by Ashutosh Bapat.

Discussion: http://postgr.es/m/e24a6a6d-5670-739b-00f3-41a226a80f25@illuminatedcomputing.com

Modifying the permissions of a persistent file isn't really much nicer
than modifying its contents, even if git doesn't currently notice it.
Adjust the test script to make a copy and set the permissions of that
instead.

Michael Paquier, per a gripe from me.  Back-patch to 9.5 where these
tests were introduced.

Discussion: https://postgr.es/m/14836.1494885946@sss.pgh.pa.us

Masahiko Sawada

Building PDFs with the new toolchain creates *.fo temporary files.

Masahiko Sawada

Discussion: http://postgr.es/m/CAD21AoAzaR_XV7j7Wk9-QYXaFoT8H4egKwXvFY63wc8Lw2C9cg@mail.gmail.com

Source-Git-URL: git://git.postgresql.org/git/pgtranslation/messages.git
Source-Git-Hash: 398beeef4921df0956f917becd7b5669d2a8a5c4

sql.sgml has not been part of the documentation since forever, so it's
pointless to keep it around.

Original coding was careless about where to insert commas.

Masahiko Sawada

Discussion: https://postgr.es/m/3427593a-61aa-b17e-64ef-383b7742d6d9@enterprisedb.com

The CommentStmt made by RebuildConstraintComment() has to pstrdup the
relation name, else it will contain a dangling pointer after that
relcache entry is flushed.  (I'm less sure that pstrdup'ing conname
is necessary, but let's be safe.)  Failure to do this leads to weird
errors or crashes, as reported by Marko Elezovic.

Bug introduced by commit e42375fc, so back-patch to 9.5 as that was.

Fix by David Rowley, regression test by Michael Paquier

Discussion: https://postgr.es/m/DB6PR03MB30775D58E732D4EB0C13725B9AE00@DB6PR03MB3077.eurprd03.prod.outlook.com

In 1753b1b0, the pg_sequence system
catalog was introduced.  This made sequence metadata changes
transactional, while the actual sequence values are still behaving
nontransactionally.  This requires some refinement in how ALTER
SEQUENCE, which operates on both, locks the sequence and the catalog.

The main problems were:

- Concurrent ALTER SEQUENCE causes "tuple concurrently updated" error,
  caused by updates to pg_sequence catalog.

- Sequence WAL writes and catalog updates are not protected by same
  lock, which could lead to inconsistent recovery order.

- nextval() disregarding uncommitted ALTER SEQUENCE changes.

To fix, nextval() and friends now lock the sequence using
RowExclusiveLock instead of AccessShareLock.  ALTER SEQUENCE locks the
sequence using ShareRowExclusiveLock.  This means that nextval() and
ALTER SEQUENCE block each other, and ALTER SEQUENCE on the same sequence
blocks itself.  (This was already the case previously for the OWNER TO,
RENAME, and SET SCHEMA variants.)  Also, rearrange some code so that the
entire AlterSequence is protected by the lock on the sequence.

As an exception, use reduced locking for ALTER SEQUENCE ... RESTART.
Since that is basically a setval(), it does not require the full locking
of other ALTER SEQUENCE actions.  So check whether we are only running a
RESTART and run with less locking if so.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
Reported-by: Jason Petersen <jason@citusdata.com>
Reported-by: Andres Freund <andres@anarazel.de>

Michael Paquier

pg_stat_get_snapshot_timestamp() returns the timestamp seen in the "global"
stats file.  Because pgstat_write_statsfiles() writes per-DB stats files
before the global file (or at least before renaming it into place), there
is a window where the test backend can see all the stats updates that
wait_for_stats() was checking for (all of which come from the per-DB file)
but also see the same global stats file it had seen at the start of the
test script.  This results in a failure in only the "snapshot_newer" query,
as reported by a couple of buildfarm members recently.

I suspect that this ought to be back-patched.  Commit 4e37b3e1 has
evidently increased the probability of this window getting hit, but
it's not apparent why it could not have been hit before.  I'll refrain
for the moment though.

Code review for commit 090010f2.

Fix cases where an elog(ERROR) partway through a function would leave the
persistent data structures in a corrupt state.  pgstat_report_stat got this
wrong by invalidating PgStat_TableEntry structs before removing hashtable
entries pointing to them, and get_tabstat_entry got it wrong by ignoring
the possibility of palloc failure after it had already created a hashtable
entry.

Also, avoid leaking a memory context per transaction, which the previous
code did through misunderstanding hash_create's API.  We do not need to
create a context to hold the hash table; hash_create will do that.
(The leak wasn't that large, amounting to only a memory context header
per iteration, but it's still surprising that nobody noticed it yet.)

Commit 60690a6f attempted to fix the wait_for_stats() function in this
test so that it would wait properly if the tenk2 scans were done in
parallel workers instead of the main session (typically as a consequence of
force_parallel_mode being turned on).  However, we made it test for whether
the main session's actions had been reported by looking for inserts on
'trunc_stats_test'.  This is the Wrong Thing, because those aren't the last
updates we expect the main session to do.  As shown by recent failures on
buildfarm member frogmouth, it's entirely likely that the trunc_stats_test
updates will be reported in a separate message from later updates, which
means there can be a window in which wait_for_stats() will exit but not all
the updates we are expecting to see will have arrived.  We should test for
the last updates we're expecting, namely those on 'trunc_stats_test4'.

Unfortunately, I doubt that this explains frogmouth's failures, because
there's no reason to believe that it's running the tenk2 queries in
parallel.  Still, the test is wrong on its own terms, so fix and back-patch
to 9.6 where parallel query came in.

Per a report from Tom Lane, newer versions of gcc apparently think
that partexprs_item_saved can be used uninitialized.  Try to convince
them otherwise.

Use the "statistics object" terminology uniformly here too.  Assorted
copy-editing.  Put new catalogs.sgml sections into alphabetical order.

Remove default cases from assorted switches over ObjectClass and some
related enum types, so that we'll get compiler warnings when someone
adds a new enum value without accounting for it in all these places.

In passing, re-order some switch cases as needed to match the declaration
of enum ObjectClass.  OK, that's just neatnik-ism, but I dislike code
that looks like it was assembled with the help of a dartboard.

Discussion: https://postgr.es/m/20170512221010.nglatgt5azzdxjlj@alvherre.pgsql

ALTER COLUMN TYPE on a column used by a statistics object fails since
commit 928c4de3, because the relevant switch in ATExecAlterColumnType
is unprepared for columns to have dependencies from OCLASS_STATISTIC_EXT
objects.

Although the existing types of extended statistics don't actually need us
to do any work for a column type change, it seems completely indefensible
that that assumption is hidden behind the failure of an unrelated module
to contain any code for the case.  Hence, create and call an API function
in statscmds.c where the assumption can be explained, and where we could
add code to deal with the problem when it inevitably becomes real.

Also, the reason this wasn't handled before, neither for extended stats
nor for the last half-dozen new OCLASS kinds :-(, is that the default:
in that switch suppresses compiler warnings, allowing people to miss the
need to consider it when adding an OCLASS.  We don't really need a default
because surely getObjectClass should only return valid values of the enum;
so remove it, and add the missed OCLASS entries where they should be.

Discussion: https://postgr.es/m/20170512221010.nglatgt5azzdxjlj@alvherre.pgsql

skewColType/skewColTypmod are no longer used in the wake of commit
9aab83fc, and seem unlikely to be wanted in future, so let's drop 'em.

Discussion: https://postgr.es/m/16364.1494520862@sss.pgh.pa.us

Consistently refer to such an entry as a "statistics object", not just
"statistics" or "extended statistics".  Previously we had a mismash of
terms, accompanied by utter confusion as to whether the term was
singular or plural.  That's not only grating (at least to the ear of
a native English speaker) but could be outright misleading, eg in error
messages that seemed to be referring to multiple objects where only one
could be meant.

This commit fixes the code and a lot of comments (though I may have
missed a few).  I also renamed two new SQL functions,
pg_get_statisticsextdef -> pg_get_statisticsobjdef
pg_statistic_ext_is_visible -> pg_statistics_obj_is_visible
to conform better with this terminology.

I have not touched the SGML docs other than fixing those function
names; the docs certainly need work but it seems like a separable task.

Discussion: https://postgr.es/m/22676.1494557205@sss.pgh.pa.us

Ultra-modern versions of the perl Data::Dumper module have apparently
changed how they indent output. Instead of trying to keep up we choose
to tell it to supporess all indentation in the hstore_plperl regression
tests.

Backpatch to 9.5 where this feature was introduced.

This should probably have been part of 60f826c5.

Reported-By: Andrew Gierth

Before 955a684e logical decoding snapshot maintenance needed to
cope with transactions it might not have seen in their entirety. For
such transactions we'd to assume they modified the catalog (could have
happened before we were watching), and thus a new snapshot had to be
built, and distributed to concurrently running transactions.

That's problematic because building a new snapshot isn't that cheap ,
especially as the the array of committed transactions needs to be
sorted.  When creating a slot on a server with a lot of transactions,
this could make logical slot creation infeasibly expensive.

After 955a684e there's no need to deal with transaction that
aren't guaranteed to be fully observable.  That allows to avoid
building snapshots for transactions that haven't modified catalog,
even before reaching consistency.

While this isn't necessarily a bugfix, slot creation being impossible
in some production workloads, is severe enough to warrant
backpatching.

Author: Andres Freund, based on a quite different patch from Petr Jelinek
Analyzed-By: Petr Jelinek
Reviewed-By: Petr Jelinek
Discussion: https://postgr.es/m/f37e975c-908f-858e-707f-058d3b1eb214@2ndquadrant.com
Backpatch: 9.4-, where logical decoding has been introduced

The snapshot assembly during the creation of logical slots relied
waiting for transactions in xl_running_xacts to end, by checking for
their commit/abort records.  Unfortunately, despite locking, it is
possible to see an xl_running_xact record listing transactions as
ready, that have already WAL-logged an commit/abort record, as the
locking just prevents the ProcArray to be adjusted, and the commit
record has to be logged first.

That lead to either delayed or hanging snapshot creation, because
snapbuild.c would wait "forever" to see commit/abort records for some
transactions.  That hang resolved only if a xl_running_xacts record
without any running transactions happened to be logged, far from
certain on a busy server.

It's impractical to prevent that via more heavyweight locking, the
likelihood of deadlocks and significantly increased contention would
be too big.

Instead change the initial snapshot creation to be solely based on
tracking the oldest running transaction via
xl_running_xacts->oldestRunningXid - that actually ends up
significantly simplifying the code.  That has two disadvantages:
1) Because we cannot fully "trust" the contents of xl_running_xacts,
   we cannot use it to build the initial snapshot.  Instead we have to
   wait twice for all running transactions to finish.
2) Previously a slot, unless the race occurred, could be created when
   the all transaction perceived as running based on commit/abort
   records, now we have to wait for the next xl_running_xacts record.
To address that, trigger logging new xl_running_xacts record from
within snapbuild.c exactly when necessary.

Unfortunately snabuild.c's SnapBuild is stored on disk, one of the
stupider ideas of a certain Mr Freund, so we can't change it in a
minor release.  As this is going to be backpatched, we have to hack
around a bit to keep on-disk compatibility.  A later commit will
rejigger that on master.

Author: Andres Freund, based on a quite different patch from Petr Jelinek
Analyzed-By: Petr Jelinek
Reviewed-By: Petr Jelinek
Discussion: https://postgr.es/m/f37e975c-908f-858e-707f-058d3b1eb214@2ndquadrant.com
Backpatch: 9.4-, where logical decoding has been introduced

The mess cleaned up in commit da075960 is clear evidence that it's a
bug hazard to expect the caller of get_attstatsslot()/free_attstatsslot()
to provide the correct type OID for the array elements in the slot.
Moreover, we weren't even getting any performance benefit from that,
since get_attstatsslot() was extracting the real type OID from the array
anyway.  So we ought to get rid of that requirement; indeed, it would
make more sense for get_attstatsslot() to pass back the type OID it found,
in case the caller isn't sure what to expect, which is likely in binary-
compatible-operator cases.

Another problem with the current implementation is that if the stats array
element type is pass-by-reference, we incur a palloc/memcpy/pfree cycle
for each element.  That seemed acceptable when the code was written because
we were targeting O(10) array sizes --- but these days, stats arrays are
almost always bigger than that, sometimes much bigger.  We can save a
significant number of cycles by doing one palloc/memcpy/pfree of the whole
array.  Indeed, in the now-probably-common case where the array is toasted,
that happens anyway so this method is basically free.  (Note: although the
catcache code will inline any out-of-line toasted values, it doesn't
decompress them.  At the other end of the size range, it doesn't expand
short-header datums either.  In either case, DatumGetArrayTypeP would have
to make a copy.  We do end up using an extra array copy step if the element
type is pass-by-value and the array length is neither small enough for a
short header nor large enough to have suffered compression.  But that
seems like a very acceptable price for winning in pass-by-ref cases.)

Hence, redesign to take these insights into account.  While at it,
convert to an API in which we fill a struct rather than passing a bunch
of pointers to individual output arguments.  That will make it less
painful if we ever want further expansion of what get_attstatsslot can
pass back.

It's certainly arguable that this is new development and not something to
push post-feature-freeze.  However, I view it as primarily bug-proofing
and therefore something that's better to have sooner not later.  Since
we aren't quite at beta phase yet, let's put it in.

Discussion: https://postgr.es/m/16364.1494520862@sss.pgh.pa.us

The fact that we didn't have this in the first place is likely why
the problem fixed by f8bffe9e
escaped detection.

Patch by Amit Langote, reviewed and slightly adjusted by me.

Discussion: http://postgr.es/m/CA+TgmoYWnV2GMnYLG-Czsix-E1WGAbo4D+0tx7t9NdfYBDMFsA@mail.gmail.com

The old logic was just plain wrong.

Report by Olaf Gawenda.  Patch by Amit Langote, reviewed by
Beena Emerson and by me.  Minor adjustments by me also.

On faster machines, the overall runtime for running the core regression
tests is under twenty seconds these days, of which the hard-wired delays
in the stats test are a significant fraction.  But on closer inspection,
it seems like we shouldn't need those.

The initial 2-second delay is there only to reduce the risk of the test's
stats messages not getting sent due to contention.  But analysis of the
last ten years' worth of buildfarm runs shows no evidence that such
failures actually occur.  (We do see failures that look like stats
messages not getting sent, particularly on Windows; but there is little
reason to believe that the initial delay reduces their frequency.)

The later 1-second delay is there to ensure that our session's stats
will have gotten sent.  But we could also do that by starting a fresh
session, which takes well under 1 second even on very slow machines.

Hence, let's remove both delays and see what happens.  The first delay
was the only test of pg_sleep_for() in the regression tests, but we can
move that responsibility into wait_for_stats().

Discussion: https://postgr.es/m/17795.1493869423@sss.pgh.pa.us