Reflecting an updated parameter value requires a server restart, which
was not mentioned in the documentation and in postgresql.conf.sample.

Reported-by: Thomas Poty
Discussion: https://postgr.es/m/15659-0cd812f13027a2d8@postgresql.org

When using a libpq client linked with OpenSSL 1.0.1 or older to connect
to a backend linked with OpenSSL 1.0.2 or newer, the server would send
SCRAM-SHA-256-PLUS and SCRAM-SHA-256 as valid mechanisms for the SASL
exchange, and the client would choose SCRAM-SHA-256-PLUS even if it does
not support channel binding, leading to a confusing error.  In this
case, what the client ought to do is switch to SCRAM-SHA-256 so as the
authentication can move on and succeed.

So for a SCRAM authentication over SSL, here are all the cases present
and how we deal with them using libpq:
1) Server supports channel binding, it sends SCRAM-SHA-256-PLUS and
SCRAM-SHA-256 as allowed mechanisms.
1-1) Client supports channel binding, chooses SCRAM-SHA-256-PLUS.
1-2) Client does not support channel binding, chooses SCRAM-SHA-256.
2) Server does not support channel binding, sends SCRAM-SHA-256 as
allowed mechanism.
2-1) Client supports channel binding, still it has no choice but to
choose SCRAM-SHA-256.
2-2) Client does not support channel binding, it chooses SCRAM-SHA-256.
In all these scenarios the connection should succeed, and the one which
was handled incorrectly prior this commit is 1-2), causing the
connection attempt to fail because client chose SCRAM-SHA-256-PLUS over
SCRAM-SHA-256.

Reported-by: Hugh Ranalli
Diagnosed-by: Peter Eisentraut
Author: Michael Paquier
Reviewed-by: Peter Eisentraut
Discussion: https://postgr.es/m/CAAhbUMO89SqUk-5mMY+OapgWf-twF2NA5sCucbHEzMfGbvcepA@mail.gmail.com
Backpatch-through: 11

It has never been used as long as hstore has been in the tree.

After ff11e7f4 Tom's compiler warns about accessing a potentially
uninitialized rInfo. That's not actually possible, but it's
understandable the compiler would get this wrong. NULL initialize too.

Reported-By: Tom Lane
Discussion: https://postgr.es/m/11199.1551285318@sss.pgh.pa.us

This can help identifying test instances more easily at run time, and
it also provides some minimal test coverage for the cluster_name
feature.
Reviewed-by: Euler Taveira <euler@timbira.com.br>
Discussion: https://www.postgresql.org/message-id/flat/1257eaee-4874-e791-e83a-46720c72cac7@2ndquadrant.com

By default, the fallback_application_name for a physical walreceiver
is "walreceiver".  This means that multiple standbys cannot be
distinguished easily on a primary, for example in pg_stat_activity or
synchronous_standby_names.

If cluster_name is set, use that for fallback_application_name in the
walreceiver.  (If it's not set, it remains "walreceiver".)  If someone
set cluster_name to identify their instance, we might as well use that
by default to identify the node remotely as well.  It's still possible
to specify another application_name in primary_conninfo explicitly.
Reviewed-by: Euler Taveira <euler@timbira.com.br>
Discussion: https://www.postgresql.org/message-id/flat/1257eaee-4874-e791-e83a-46720c72cac7@2ndquadrant.com

The leak has been introduced by 763f2edd which has addressed the problem
for transient tables, and forgot CREATE TABLE AS which shares a similar
logic when receiving a new tuple to store into the newly-created
relation.

Author: Jeff Janes
Discussion: https://postgr.es/m/CAMkU=1xZXtz3mziPEPD2Fubbas4G2RWkZm5HHABtfKVcbu1=Sg@mail.gmail.com

In preparation for abstracting table storage, convert trigger.c to
track tuples in slots. Which also happens to make code calling
triggers simpler.

As the calling interface for triggers themselves is not changed in
this patch, HeapTuples still are extracted from the slot at that
time. But that's handled solely inside trigger.c, not visible to
callers. It's quite likely that we'll want to revise the external
trigger interface, but that's a separate large project.

As part of this work the slots used for old/new/return tuples are
moved from EState into ResultRelInfo, as different updated tables
might need different slots. The slots are now also now created
on-demand, which is good both from an efficiency POV, but also makes
the modifying code simpler.

Author: Andres Freund, Amit Khandekar and Ashutosh Bapat
Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de

After the introduction of tuple table slots all table AMs need to
support returning the table oid of the tuple stored in a slot created
by said AM. It does not make sense to re-implement that in every AM,
therefore move handling of table OIDs into the TupleTableSlot
structure itself.  It's possible that we, at a later date, might want
to get rid of HeapTupleData.t_tableOid entirely, but doing so before
the abstractions for table AMs are integrated turns out to be too
hard, so delay that for now.

Similarly, every AM needs to support the concept of a tuple
identifier (tid / item pointer) for its tuples. It's quite possible
that we'll generalize the exact form of a tid at a future point (to
allow for things like index organized tables), but for now many parts
of the code know about tids, so there's not much point in abstracting
tids away. Therefore also move into slot (rather than providing API to
set/get the tid associated with the tuple in a slot).

Once table AM includes insert/updating/deleting tuples, the
responsibility to set the correct tid after such an action will move
into that. After that change, code doing such modifications, should
not have to deal with HeapTuples directly anymore.

Author: Andres Freund, Haribabu Kommi and Ashutosh Bapat
Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de

That avoids having to care about the lifetime of the
HeapTupleHeaderData passed to ExecStore[Buffer]HeapTuple(). That
doesn't make a huge difference for a plain HeapTupleTableSlot, but for
BufferHeapTupleTableSlot it can be a significant advantage, avoiding
the need to materialize slots where it's inconvenient to provide a
HeapTupleData with appropriate lifetime to point to the on-disk tuple.

It's quite possible that we'll want to add support functions for
constructing HeapTuples using that embedded HeapTupleData, but for now
callers do so themselves.

Author: Andres Freund
Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de

This allows to avoid an unnecessary pin/unpin cycle when storing a
tuple in an already pinned buffer into a slot, when the pin isn't
further needed at the call site.

Only a single caller for now (to ensure coverage), but upcoming
patches will increase use of the new function.

Author: Andres Freund
Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de

Previously, this function acquired locks in the order using
find_all_inheritors(), which locks the children of each table that it
processes in ascending OID order, and which processes the inheritance
hierarchy as a whole in a breadth-first fashion.  Now, it processes
the inheritance hierarchy in a depth-first fashion, and at each level
it proceeds in the order in which tables appear in the PartitionDesc.
If table inheritance rather than table partitioning is used, the old
order is preserved.

This change moves the locking of any given partition much closer to
the code that actually expands that partition.  This seems essential
if we ever want to allow concurrent DDL to add or remove partitions,
because if the set of partitions can change, we must use the same data
to decide which partitions to lock as we do to decide which partitions
to expand; otherwise, we might expand a partition that we haven't
locked.  It should hopefully also facilitate efforts to postpone
inheritance expansion or locking for performance reasons, because
there's really no way to postpone locking some partitions if
we're blindly locking them all using find_all_inheritors().

The only downside of this change which is known to me is that it
further deviates from the principle that we should always lock the
inheritance hierarchy in find_all_inheritors() order to avoid deadlock
risk.  However, we've already crossed that bridge in commit
9eefba18 and there are futher patches
pending that make similar changes, so this isn't really giving up
anything that we haven't surrendered already -- and it seems entirely
worth it, given the performance benefits some of those changes seem
likely to bring.

Patch by me; thanks to David Rowley for discussion of these issues.

Discussion: http://postgr.es/m/CAKJS1f_eEYVEq5tM8sm1k-HOwG0AyCPwX54XG9x4w0zy_N4Q_Q@mail.gmail.com
Discussion: http://postgr.es/m/CA+TgmoZUwPf_uanjF==gTGBMJrn8uCq52XYvAEorNkLrUdoawg@mail.gmail.com

While not really a problem it's easier to run tools like valgrind against it
when fixed.

9a4059d4 simplified the flush of target data folder when finishing
processing, and could have done a bit more.

Discussion: https://postgr.es/m/20190131064759.GA13429@paquier.xyz

_bt_getstackbuf() is called at exactly two points following commit
efada2b8 (one call site is concerned with page splits, while the
other is concerned with page deletion).  The parent buffer returned by
_bt_getstackbuf() is write-locked in both cases.  Remove the 'access'
argument and make _bt_getstackbuf() assume that callers require a
write-lock.

Commit efada2b8, which made the nbtree page deletion algorithm more
robust, removed _bt_getstackbuf() calls from _bt_pagedel().  It failed
to update a comment that referenced the earlier approach.  Update the
comment to explain that the _bt_getstackbuf() page deletion call site
mirrors the only other remaining _bt_getstackbuf() call site, which is
reached during page splits.

The check in create_help.pl for a null end tag (</>) has been obsolete
since the conversion from SGML to XML, since XML does not allow that
anymore.

Remove some unnecessary, legacy-looking use of the PROCEDURAL keyword
before LANGUAGE.  We mostly don't use this anymore, so some of these
look a bit old.

There is still some use in pg_dump, which is harder to remove because
it's baked into the archive format, so I'm not touching that.

Discussion: https://www.postgresql.org/message-id/2330919b-62d9-29ac-8de3-58c024fdcb96@2ndquadrant.com

When preparing a transaction in two-phase commit, a dummy PGPROC entry
holding the GID used for the transaction is registered, which gets
released once COMMIT PREPARED is run.  Prior releasing its shared memory
state, all the locks taken in the prepared transaction are released
using a dedicated set of callbacks (pgstat and multixact having similar
callbacks), which may cause the locks to be released before the GID is
set free.

Hence, there is a small window where lock conflicts could happen, for
example:
- Transaction A releases its locks, still holding its GID in shared
memory.
- Transaction B held a lock which conflicted with locks of transaction
A.
- Transaction B continues its processing, reusing the same GID as
transaction A.
- Transaction B fails because of a conflicting GID, already in use by
transaction A.

This commit changes the shared memory state release so as post-commit
callbacks and predicate lock cleanup happen consistently with the shared
memory state cleanup for the dummy PGPROC entry.  The race window is
small and 2PC had this issue from the start, so no backpatch is done.
On top if that fixes discussed involved ABI breakages, which are not
welcome in stable branches.

Reported-by: Oleksii Kliukin, Ildar Musin
Diagnosed-by: Oleksii Kliukin, Ildar Musin
Author: Michael Paquier
Reviewed-by: Masahiko Sawada, Oleksii Kliukin
Discussion: https://postgr.es/m/BF9B38A4-2BFF-46E8-BA87-A2D00A8047A6@hintbits.com

Commit 16be2fd1 introduced the flag DSA_ALLOC_NO_OOM to control whether
the DSA allocator would raise an error or return InvalidDsaPointer on
failure to allocate.  One edge case was not handled correctly: if we
fail to allocate an internal "span" object for a large allocation, we
would always return InvalidDsaPointer regardless of the flag; a caller
not expecting that could then dereference a null pointer.

This is a plausible explanation for a one-off report of a segfault.

Remove a redundant pair of braces so that all three stanzas that handle
DSA_ALLOC_NO_OOM match in style, for visual consistency.

While fixing inconsistencies, if FreePageManagerGet() can't supply the
pages that our book-keeping says it should be able to supply, then we
should always report a FATAL error.  Previously we treated that as a
regular allocation failure in one code path, but as a FATAL condition
in another.

Back-patch to 10, where dsa.c landed.

Author: Thomas Munro
Reported-by: Jakub Glapa
Discussion: https://postgr.es/m/CAEepm=2oPqXxyWQ-1o60tpOLrwkw=VpgNXqqF1VN2EyO9zKGQw@mail.gmail.com

The Bison documentation clearly states that a semicolon is required
after every grammar rule, and our scripts that generate ecpg's
grammar from the backend's implicitly assumed this is true.  But it
turns out that only ancient versions of Bison actually enforce that.
There have been a couple of rules without trailing semicolons in
gram.y for some time, and as a consequence, ecpg's grammar was faulty
and produced wrong output for the affected statements.

To fix, add the missing semis, and add some cross-checks to ecpg's
scripts so that they'll bleat if we mess this up again.

The cases that were broken were:
* "SET variable = DEFAULT" (but not "SET variable TO DEFAULT"),
  as well as allied syntaxes such as ALTER SYSTEM SET ... DEFAULT.
  These produced syntactically invalid output that the server
  would reject.
* Multiple type names in DROP TYPE/DOMAIN commands.  Only the
  first type name would be listed in the emitted command.

Per report from Daisuke Higuchi.  Back-patch to all supported versions.

Discussion: https://postgr.es/m/1803D792815FC24D871C00D17AE95905DB51CE@g01jpexmbkw24

Previously, we tolerated EBADF as a way for the operating system to
indicate that it doesn't support fsync() on a directory.  Tolerate
EINVAL too, for older versions of Linux CIFS.

Bug #15636.  Back-patch all the way.

Reported-by: John Klann
Discussion: https://postgr.es/m/15636-d380890dafd78fc6@postgresql.org

One unintended consequence of commit 9ccdd7f6 was that Windows WSL
users started getting a panic whenever we tried to initiate data
flushing with sync_file_range(), because WSL does not implement that
system call.  Previously, they got a stream of periodic warnings,
which was also undesirable but at least ignorable.

Prevent the panic by handling ENOSYS specially and skipping the panic
promotion with data_sync_elevel().  Also suppress future attempts
after the first such failure so that the pre-existing problem of
noisy warnings is improved.

Back-patch to 9.6 (older branches were not affected in this way by
9ccdd7f6).

Author: Thomas Munro and James Sewell
Tested-by: James Sewell
Reported-by: Bruce Klein
Discussion: https://postgr.es/m/CA+mCpegfOUph2U4ZADtQT16dfbkjjYNJL1bSTWErsazaFjQW9A@mail.gmail.com

This reverts commit 1995552d.

Several developers didn't like the new behavior.

The header block of TwoPhaseGetDummyBackendId mentioned incorrectly
TwoPhaseGetDummyProc.

Reported-by: Oleksii Kliukin
Discussion: https://postgr.es/m/D8336E40-BBE1-4954-98BB-7830D3F5CB36@hintbits.com

The current set of TAP tests for two-phase transactions include some
coverage for post-commit callbacks of multixact, but it lacked tests for
testing the recovery of those callbacks.  This commit adds some tests
with soft and hard restarts in this case, using transactions which
include DDLs.

Author: Michael Paquier
Reviewed-by: Oleksii Kliukin
Discussion: https://postgr.es/m/20190221055431.GO15532@paquier.xyz

In the case where inheritance_planner() finds that every table has
been excluded by constraints, it thought it could get away with
making a plan consisting of just a dummy Result node.  While certainly
there's no updating or deleting to be done, this had two user-visible
problems: the plan did not report the correct set of output columns
when a RETURNING clause was present, and if there were any
statement-level triggers that should be fired, it didn't fire them.

Hence, rather than only generating the dummy Result, we need to
stick a valid ModifyTable node on top, which requires a tad more
effort here.

It's been broken this way for as long as inheritance_planner() has
known about deleting excluded subplans at all (cf commit 635d42e9),
so back-patch to all supported branches.

Amit Langote and Tom Lane, per a report from Petr Fedorov.

Discussion: https://postgr.es/m/5da6f0f0-1364-1876-6978-907678f89a3e@phystech.edu

We were reporting the database name instead of the relation name to
pg_stat_activity.  Repair.

Reported-by: Justin Pryzby
Discussion: https://postgr.es/m/20190220185552.GR28750@telsasoft.com

New code introduced in 050710b3.  The
lack of const is not currently a compiler warning, but it's nice to
have for consistency with surrounding code.

The same variables are declared twice when checking if a connection is
writable, which is useless.

Author: Haribabu Kommi
Discussion: https://postgr.es/m/CAJrrPGf=rcALB54w_Tg1_hx3y+cgSWaERY-uYSQzGc3Zt5XN4g@mail.gmail.com

There isn't any good reason for this test to be a self-join rather
than a join between separate tables, except that it saved a couple
of SQL commands for setup.  A proposed patch to optimize away
self-joins breaks the test, so adjust it to avoid that happening.

Discussion: https://postgr.es/m/64486b0b-0404-e39e-322d-0801154901f3@postgrespro.ru

It seems to make more sense for this to be in selfuncs.c, since it's
largely a statistical-estimation thing, and it's related to other
functions like estimate_hash_bucket_stats that are there.

While at it, change the result type from Size to double.  Perhaps at one
point it was impossible for the result to overflow an integer, but
I've got no confidence in that proposition anymore.  Nothing's actually
done with the result except to compare it to a work_mem-based limit,
so as long as we don't get an overflow on the way to that comparison,
things should be fine even with very large dNumGroups.

Code movement proposed by Antonin Houska, type change by me

Discussion: https://postgr.es/m/25767.1549359615@localhost

Change pg_stat_ssl so that an unprivileged user can only see their own
rows; other rows will be all null.  This makes the behavior consistent
with pg_stat_activity, where information about where the connection
came from is also restricted.
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://www.postgresql.org/message-id/flat/63117976-d02c-c8e2-3aef-caa31a5ab8d3%402ndquadrant.com

Add a basic note that some columns in pg_stat_activity and related
views are not visible to all users.

Discussion: https://www.postgresql.org/message-id/3018acd9-e5d8-1e85-5ed7-47276cd77569%402ndquadrant.com

Don't expand inputfile and outputfile to absolute paths globally, just
where needed.  In particular, pass them as is to the file name
arguments of the diff command, so that we don't see the full absolute
path in the diff header, which makes the diff unnecessarily verbose
and harder to read.

Discussion: https://www.postgresql.org/message-id/0cc82900-c457-1cee-3ab2-7b0f5d215061@2ndquadrant.com

This is similar in spirit to the existing partbounds.c file in the
same directory, except that there's a lot less code in the new file
created by this commit.  Pending work in this area proposes to add a
bunch more code related to PartitionDescs, though, and this will give
us a good place to put it.

Discussion: http://postgr.es/m/CA+TgmoZUwPf_uanjF==gTGBMJrn8uCq52XYvAEorNkLrUdoawg@mail.gmail.com

Instead of locking all partitions to which we might route a tuple at
executor startup, just lock them as we use them.  In some cases such a
partition might get locked at executor startup anyway because it
appears in the query's range table for some other reason, but in other
cases this is a bit savings.

This changes the order in which partitions are locked in some cases,
which might conceivably create deadlock hazards that don't exist
today, but per discussion, it seems like such cases should be rare
enough that we can neglect them in favor of improving performance.

David Rowley, reviewed and tested by Tomas Vondra, Sho Kato, John
Naylor, Tom Lane, and me.

Discussion: http://postgr.es/m/CAKJS1f-=FnMqmQP6qitkD+xEddxw22ySLP-0xFk3JAqUX2yfMw@mail.gmail.com

In previous releases, the input file of dbtoepub was postgres.xml, and
dbtoepub knows to derive the output file name postgres.epub from that
automatically.  But now the intput file is postgres.sgml (since
postgres.sgml is itself an XML file and we no longer need the
intermediate postgres.xml file), but dbtoepub doesn't know how to deal
with the .sgml suffix, so the automatically derived output file name
becomes postgres.sgml.epub.  Fix by adding an explicit -o option.

Check ec_relids before bothering to iterate through the EC members.
On a perhaps extreme, but still real-world, query in which
match_eclasses_to_foreign_key_col() accounts for the bulk of the
planner's runtime, this saves nearly 40% of the runtime.  It's a bit
of a stopgap fix, but it's simple enough to be back-patched to 9.6
where this code came in; so let's do that.

David Rowley

Discussion: https://postgr.es/m/6970.1545327857@sss.pgh.pa.us