On both the frontend and backend, prepare for GSSAPI encryption
support by moving common code for error handling into a separate file.
Fix a TODO for handling multiple status messages in the process.
Eliminate the OIDs, which have not been needed for some time.

Add frontend and backend encryption support functions.  Keep the
context initiation for authentication-only separate on both the
frontend and backend in order to avoid concerns about changing the
requested flags to include encryption support.

In postmaster, pull GSSAPI authorization checking into a shared
function.  Also share the initiator name between the encryption and
non-encryption codepaths.

For HBA, add "hostgssenc" and "hostnogssenc" entries that behave
similarly to their SSL counterparts.  "hostgssenc" requires either
"gss", "trust", or "reject" for its authentication.

Similarly, add a "gssencmode" parameter to libpq.  Supported values are
"disable", "require", and "prefer".  Notably, negotiation will only be
attempted if credentials can be acquired.  Move credential acquisition
into its own function to support this behavior.

Add a simple pg_stat_gssapi view similar to pg_stat_ssl, for monitoring
if GSSAPI authentication was used, what principal was used, and if
encryption is being used on the connection.

Finally, add documentation for everything new, and update existing
documentation on connection security.

Thanks to Michael Paquier for the Windows fixes.

Author: Robbie Harwood, with changes to the read/write functions by me.
Reviewed in various forms and at different times by: Michael Paquier,
   Andres Freund, David Steele.
Discussion: https://www.postgresql.org/message-id/flat/jlg1tgq1ktm.fsf@thriss.redhat.com

We were passing a string owned by a syscache entry, which was released
before recursing.  Fix by pstrdup'ing the string.

Per buildfarm member prion.

Previously, while primary keys could be made on partitioned tables, it
was not possible to define foreign keys that reference those primary
keys.  Now it is possible to do that.

Author: Álvaro Herrera
Reviewed-by: Amit Langote, Jesper Pedersen
Discussion: https://postgr.es/m/20181102234158.735b3fevta63msbj@alvherre.pgsql

Instead of WAL-logging every modification during the build separately,
first build the index without any WAL-logging, and make a separate pass
through the index at the end, to write all pages to the WAL. This
significantly reduces the amount of WAL generated, and is usually also
faster, despite the extra I/O needed for the extra scan through the index.
WAL generated this way is also faster to replay.

For GiST, the LSN-NSN interlock makes this a little tricky. All pages must
be marked with a valid (i.e. non-zero) LSN, so that the parent-child
LSN-NSN interlock works correctly. We now use magic value 1 for that during
index build. Change the fake LSN counter to begin from 1000, so that 1 is
safely smaller than any real or fake LSN. 2 would've been enough for our
purposes, but let's reserve a bigger range, in case we need more special
values in the future.

Author: Anastasia Lubennikova, Andrey V. Lepikhov
Reviewed-by: Heikki Linnakangas, Dmitry Dolgov

Valgrind was rightly complaining that IndexVacuumInfo->report_progress
(added by commit ab0dfc96) was not being initialized in some code
paths.  Repair.

Per buildfarm member lousyjack.

Per buildfarm member longfin.

Pilot error in previous commit

This uses the progress reporting infrastructure added by c16dc1ac,
adding support for CREATE INDEX and CREATE INDEX CONCURRENTLY.

There are two pieces to this: one is index-AM-agnostic, and the other is
AM-specific.  The latter is fairly elaborate for btrees, including
reportage for parallel index builds and the separate phases that btree
index creation uses; other index AMs, which are much simpler in their
building procedures, have simplistic reporting only, but that seems
sufficient, at least for non-concurrent builds.

The index-AM-agnostic part is fairly complete, providing insight into
the CONCURRENTLY wait phases as well as block-based progress during the
index validation table scan.  (The index validation index scan requires
patching each AM, which has not been included here.)

Reviewers: Rahila Syed, Pavan Deolasee, Tatsuro Yamada
Discussion: https://postgr.es/m/20181220220022.mg63bhk26zdpvmcj@alvherre.pgsql

When asked for a slice of a TOAST entry, decompress enough to return the
slice instead of decompressing the entire object.

For use cases where the slice is at, or near, the beginning of the entry,
this avoids a lot of unnecessary decompression work.

This changes the signature of pglz_decompress() by adding a boolean to
indicate if it's ok for the call to finish before consuming all of the
source or destination buffers.

Author: Paul Ramsey
Reviewed-By: Rafia Sabih, Darafei Praliaskouski, Regina Obe
Discussion: https://postgr.es/m/CACowWR07EDm7Y4m2kbhN_jnys%3DBBf9A6768RyQdKm_%3DNpkcaWg%40mail.gmail.com

The upper-planner pathification allows FDWs to arrange to push down
different types of upper-stage operations to the remote side.  This
commit teaches postgres_fdw to do it for the (FINAL, NULL) upperrel,
which is responsible for doing LockRows, LIMIT, and/or ModifyTable.
This provides the ability for postgres_fdw to handle SELECT commands
so that it 1) skips the LockRows step (if any) (note that this is
safe since it performs early locking) and 2) pushes down the LIMIT
and/or OFFSET restrictions (if any) to the remote side.  This doesn't
handle the INSERT/UPDATE/DELETE cases.

Author: Etsuro Fujita
Reviewed-By: Antonin Houska and Jeff Janes
Discussion: https://postgr.es/m/87pnz1aby9.fsf@news-spur.riddles.org.uk

This is in preparation for an upcoming commit.

Author: Etsuro Fujita
Reviewed-By: Antonin Houska and Jeff Janes
Discussion: https://postgr.es/m/87pnz1aby9.fsf@news-spur.riddles.org.uk

This prevents the tests added by commit 4bbf6edf and adjusted by
commit 99f6a17d from being useless by plan changes created by an
upcoming commit.

Author: Etsuro Fujita
Discussion: https://postgr.es/m/87pnz1aby9.fsf@news-spur.riddles.org.uk

The upper-planner pathification allows FDWs to arrange to push down
different types of upper-stage operations to the remote side.  This
commit teaches postgres_fdw to do it for the (ORDERED, NULL) upperrel,
which is responsible for evaluating the query's ORDER BY ordering.
Since postgres_fdw is already able to evaluate that ordering remotely
for foreign baserels and foreign joinrels (see commit aa09cd24 et al.),
this adds support for that for foreign grouping relations.

Author: Etsuro Fujita
Reviewed-By: Antonin Houska and Jeff Janes
Discussion: https://postgr.es/m/87pnz1aby9.fsf@news-spur.riddles.org.uk

When accessing a table with RLS via a view, the RLS checks are
performed as the view owner. However, the code neglected to propagate
that to any subqueries in the RLS checks. Fix that by calling
setRuleCheckAsUser() for all RLS policy quals and withCheckOption
checks for RTEs with RLS.

Back-patch to 9.5 where RLS was added.

Per bug #15708 from daurnimator.

Discussion: https://postgr.es/m/15708-d65cab2ce9b1717a@postgresql.org

This adds a new option to pg_checksums called -P/--progress, showing
every second some information about the computation state of an
operation for --check and --enable (--disable only updates the control
file and is quick).  This requires a pre-scan of the data folder so as
the total size of checksummable items can be calculated, and then it
gets compared to the amount processed.

Similarly to what is done for pg_rewind and pg_basebackup, the
information printed in the progress report consists of the current
amount of data computed and the total amount of data to compute.  This
could be extended later on.

Author: Michael Banck, Bernd Helmle
Reviewed-by: Fabien Coelho, Michael Paquier
Discussion: https://postgr.es/m/1535719851.1286.17.camel@credativ.de

On at least ZFS, it can be beneficial to create new WAL files every
time and not to bother zero-filling them.  Since it's not clear which
other filesystems might benefit from one or both of those things,
add individual GUCs to control those two behaviors independently and
make only very general statements in the docs.

Author: Jerry Jelinek, with some adjustments by Thomas Munro
Reviewed-by: Alvaro Herrera, Andres Freund, Tomas Vondra, Robert Haas and others
Discussion: https://postgr.es/m/CACPQ5Fo00QR7LNAcd1ZjgoBi4y97%2BK760YABs0vQHH5dLdkkMA%40mail.gmail.com

Contrib modules pgrowlocks, pgstattuple and some functionality in
pageinspect currently only supports the heap table AM. As they are all
concerned with low-level details that aren't reasonably exposed via
tableam, error out if invoked on a non heap relation.

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

This replaces the previous calls of heap_sync() in places using
bulk-insert. By passing in the flags used for bulk-insert the AM can
decide (first at insert time and then during the finish call) which of
the optimizations apply to it, and what operations are necessary to
finish a bulk insert operation.

Also change HEAP_INSERT_* flags to TABLE_INSERT, and rename hi_options
to ti_options.

These changes are made even in copy.c, which hasn't yet been converted
to tableam. There's no harm in doing so.

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

Remove the code that supported zipfian distribution parameters less
than 1.0, as it had undocumented performance hazards, and it's not
clear that the case is useful enough to justify either fixing or
documenting those hazards.

Also, since the code path for parameter > 1.0 could perform badly
for values very close to 1.0, establish a minimum allowed value
of 1.001.  This solution seems superior to the previous vague
documentation warning about small values not performing well.

Fabien Coelho, per a gripe from Tomas Vondra

Discussion: https://postgr.es/m/b5e172e9-ad22-48a3-86a3-589afa20e8f7@2ndquadrant.com

We can't call code that uses syscache while we hold buffer locks
on a catalog relation.  If passed such a relation, just fall back
to the general effective_io_concurrency GUC rather than trying to
look up the containing tablespace's IO concurrency setting.

We might find a better way to control prefetching in follow-up
work, but for now this is enough to avoid the deadlock introduced
by commit 558a9165.

Reviewed-by: Andres Freund
Diagnosed-by: Peter Geoghegan
Discussion: https://postgr.es/m/CA%2BhUKGLCwPF0S4Mk7S8qw%2BDK0Bq65LueN9rofAA3HHSYikW-Zw%40mail.gmail.com
Discussion: https://postgr.es/m/962831d8-c18d-180d-75fb-8b842e3a2742%40chrullrich.net

Add a section explaining how our XML features depart from current
versions of the SQL standard.  Update and clarify the descriptions
of some XML functions.

Chapman Flack, reviewed by Ryan Lambert

Discussion: https://postgr.es/m/5BD1284C.1010305@anastigmatix.net
Discussion: https://postgr.es/m/5C81F8C0.6090901@anastigmatix.net
Discussion: https://postgr.es/m/CAN-V+g-6JqUQEQZ55Q3toXEN6d5Ez5uvzL4VR+8KtvJKj31taw@mail.gmail.com

Noted by Pavel Stehule

Discussion: https://postgr.es/m/CAFj8pRAaGO5FX7bnP3E=mRssoK8y5T78x7jKy-vDiyS68L888Q@mail.gmail.com

This unifies the various ad hoc logging (message printing, error
printing) systems used throughout the command-line programs.

Features:

- Program name is automatically prefixed.

- Message string does not end with newline.  This removes a common
  source of inconsistencies and omissions.

- Additionally, a final newline is automatically stripped, simplifying
  use of PQerrorMessage() etc., another common source of mistakes.

- I converted error message strings to use %m where possible.

- As a result of the above several points, more translatable message
  strings can be shared between different components and between
  frontends and backend, without gratuitous punctuation or whitespace
  differences.

- There is support for setting a "log level".  This is not meant to be
  user-facing, but can be used internally to implement debug or
  verbose modes.

- Lazy argument evaluation, so no significant overhead if logging at
  some level is disabled.

- Some color in the messages, similar to gcc and clang.  Set
  PG_COLOR=auto to try it out.  Some colors are predefined, but can be
  customized by setting PG_COLORS.

- Common files (common/, fe_utils/, etc.) can handle logging much more
  simply by just using one API without worrying too much about the
  context of the calling program, requiring callbacks, or having to
  pass "progname" around everywhere.

- Some programs called setvbuf() to make sure that stderr is
  unbuffered, even on Windows.  But not all programs did that.  This
  is now done centrally.

Soft goals:

- Reduces vertical space use and visual complexity of error reporting
  in the source code.

- Encourages more deliberate classification of messages.  For example,
  in some cases it wasn't clear without analyzing the surrounding code
  whether a message was meant as an error or just an info.

- Concepts and terms are vaguely aligned with popular logging
  frameworks such as log4j and Python logging.

This is all just about printing stuff out.  Nothing affects program
flow (e.g., fatal exits).  The uses are just too varied to do that.
Some existing code had wrappers that do some kind of print-and-exit,
and I adapted those.

I tried to keep the output mostly the same, but there is a lot of
historical baggage to unwind and special cases to consider, and I
might not always have succeeded.  One significant change is that
pg_rewind used to write all error messages to stdout.  That is now
changed to stderr.
Reviewed-by: Donald Dong <xdong@csumb.edu>
Reviewed-by: Arthur Zakirov <a.zakirov@postgrespro.ru>
Discussion: https://www.postgresql.org/message-id/flat/6a609b43-4f57-7348-6480-bd022f924310@2ndquadrant.com

jsonb_path_match() checks if jsonb document matches jsonpath query.  Therefore,
jsonpath query should return single boolean.  Currently, if result of jsonpath
is not a single boolean, NULL is returned independently whether silent mode
is on or off.  But that appears to be wrong when silent mode is off.  This
commit makes jsonb_path_match() throw an error in this case.

Author: Nikita Glukhov

Jsonpath now accepts integers with leading zeroes and floats starting with
a dot.  However, SQL standard requires to follow JSON specification, which
doesn't allow none of these cases.  Our json[b] datatypes also restrict that.
So, restrict it in jsonpath altogether.

Author: Nikita Glukhov

This commit makes existing GIN operator classes jsonb_ops and json_path_ops
support "jsonb @@ jsonpath" and "jsonb @? jsonpath" operators.  Basic idea is
to extract statements of following form out of jsonpath.

 key1.key2. ... .keyN = const

The rest of jsonpath is rechecked from heap.

Catversion is bumped.

Discussion: https://postgr.es/m/fcc6fc6a-b497-f39a-923d-aa34d0c588e8%402ndQuadrant.com
Author: Nikita Glukhov, Alexander Korotkov
Reviewed-by: Jonathan Katz, Pavel Stehule

The syntax

    GENERATED BY DEFAULT AS (expr)

is not allowed but we have to accept it in the grammar to avoid
shift/reduce conflicts because of the similar syntax for identity
columns.  The existing code just ignored this, incorrectly.  Add an
explicit error check and a bespoke error message.
Reported-by: Justin Pryzby <pryzby@telsasoft.com>

Spotted by Coverity.

One should almost always terminate an old process, not use a manual
removal tool like ipcrm.  Removal of the ipcclean script eleven years
ago (39627b1a) and its non-replacement
corroborate that manual shm removal is now a niche goal.  Back-patch to
9.4 (all supported versions).

Reviewed by Daniel Gustafsson and Kyotaro HORIGUCHI.

Discussion: https://postgr.es/m/20180812064815.GB2301738@rfd.leadboat.com

This moves bitmap heap scan support to below an optional tableam
callback. It's optional as the whole concept of bitmap heapscans is
fairly block specific.

This basically moves the work previously done in bitgetpage() into the
new scan_bitmap_next_block callback, and the direct poking into the
buffer done in BitmapHeapNext() into the new scan_bitmap_next_tuple()
callback.

The abstraction is currently somewhat leaky because
nodeBitmapHeapscan.c's prefetching and visibilitymap based logic
remains - it's likely that we'll later have to move more into the
AM. But it's not trivial to do so without introducing a significant
amount of code duplication between the AMs, so that's a project for
later.

Note that now nodeBitmapHeapscan.c and the associated node types are a
bit misnamed. But it's not clear whether renaming wouldn't be a cure
worse than the disease. Either way, that'd be best done in a separate
commit.

Author: Andres Freund
Reviewed-By: Robert Haas (in an older version)
Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de

This moves sample scan support to below tableam. It's not optional as
there is, in contrast to e.g. bitmap heap scans, no alternative way to
perform tablesample queries. If an AM can't deal with the block based
API, it will have to throw an ERROR.

The tableam callbacks for this are block based, but given the current
TsmRoutine interface, that seems to be required.

The new interface doesn't require TsmRoutines to perform visibility
checks anymore - that requires the TsmRoutine to know details about
the AM, which we want to avoid.  To continue to allow taking the
returned number of tuples account SampleScanState now has a donetuples
field (which previously e.g. existed in SystemRowsSamplerData), which
is only incremented after the visibility check succeeds.

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

The superflous heapam_xlog.h includes were reported by Peter
Geoghegan.

Commit 29b64d1d mishandled skipping over truncated high key attributes
during row comparisons.  The row comparison key matching loop would loop
forever when a truncated attribute was encountered for a row compare
subkey.  Fix by following the example of other code in the loop: advance
the current subkey, or break out of the loop when the last subkey is
reached.

Add test coverage for the relevant _bt_check_rowcompare() code path.
The new test case is somewhat tied to nbtree implementation details,
which isn't ideal, but seems unavoidable.

There was some debate about whether the code I'd added to remap
AppendRelInfos obtained from the initial SELECT planning run is
actually necessary.  Add a test case demonstrating that it is.

Discussion: https://postgr.es/m/23831.1553873385@sss.pgh.pa.us

We can set this up once and for all in subquery_planner's initial survey
of the flattened rangetable, rather than incrementally adjusting it in
build_simple_rel.  The previous approach made it rather hard to reason
about exactly when the value would be available, and we were definitely
using it in some places before the final value was computed.

Noted while fooling around with Amit Langote's patch to delay creation
of inheritance child rels.  That didn't break this code, but it made it
even more fragile, IMO.

An anti-wraparound vacuum has to be by definition aggressive as it needs
to work on all the pages of a relation.  However it can happen that due
to some concurrent activity an anti-wraparound vacuum is marked as
non-aggressive, which makes it redundant with a previous run, and
it is actually useless as an anti-wraparound vacuum should process all
the pages of a relation.  This commit makes such vacuums to be skipped.

An anti-wraparound vacuum not aggressive can be found easily by mixing
low values of autovacuum_freeze_max_age (to control anti-wraparound) and
autovacuum_freeze_table_age (to control the aggressiveness).

28a8fa98 has added some extra logging printing all the possible
combinations of anti-wraparound and aggressive vacuums, which now gets
simplified as an anti-wraparound vacuum also non-aggressive gets
skipped.

Per discussion mainly between Andrew Dunstan, Robert Haas, Álvaro
Herrera, Kyotaro Horiguchi, Masahiko Sawada, and myself.

Author: Kyotaro Horiguchi, Michael Paquier
Reviewed-by: Andrew Dunstan, Álvaro Herrera
Discussion: https://postgr.es/m/20180914153554.562muwr3uwujno75@alvherre.pgsql

Backpatch to 9.5, when pg_upgrade's location changed.

Discussion: https://postgr.es/m/5506b8fa-7dad-8483-053c-7ca7ef04f01a@2ndQuadrant.com

This just moves the table/matview[/toast] determination of relation
size to a callback, and uses a copy of the existing logic to implement
that callback for heap.

It probably would make sense to also move the index specific logic
into a callback, so the metapage handling (and probably more) can be
index specific. But that's a separate task.

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

This is a relatively straightforward move of the current
implementation to sit below tableam. As the current analyze sampling
implementation is pretty inherently block based, the tableam analyze
interface is as well. It might make sense to generalize that at some
point, but that seems like a larger project that shouldn't be
undertaken at the same time as the introduction of tableam.

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

Author: John Naylor