Now that commit 62f34097 attached BKI_LOOKUP annotation to all the
namespace and role OID columns in the catalogs, there's no real reason
to have the magic PGNSP and PGUID symbols.  Get rid of them in favor
of implementing those lookups according to genbki.pl's normal pattern.

This means that in the catalog headers, BKI_DEFAULT(PGNSP) becomes
BKI_DEFAULT(pg_catalog), which seems a lot more transparent.
BKI_DEFAULT(PGUID) becomes BKI_DEFAULT(POSTGRES), which is perhaps
less so; but you can look into pg_authid.dat to discover that
POSTGRES is the nonce name for the bootstrap superuser.

This change also means that if we ever need cross-references in the
initial catalog data to any of the other built-in roles besides
POSTGRES, or to some other built-in schema besides pg_catalog,
we can just do it.

No catversion bump here, as there's no actual change in the contents
of postgres.bki.

Discussion: https://postgr.es/m/3240355.1612129197@sss.pgh.pa.us

Generation expressions of generated columns are always inherited, so
there is no need to set them separately in child tables, and there is
no syntax to do so either.  The code previously used the code paths
for the handling of default values, for which different rules apply;
in particular it might want to set a default value explicitly for an
inherited column.  This resulted in unrestorable dumps.  For generated
columns, just skip them in inherited tables.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/15830.1575468847%40sss.pgh.pa.us

In the wake of commit 62f34097, we no longer need this tool.

Discussion: https://postgr.es/m/3240355.1612129197@sss.pgh.pa.us

This follows in the spirit of commit dfb75e47, which created primary
key and uniqueness constraints to improve the visibility of constraints
imposed on the system catalogs.  While our catalogs contain many
foreign-key-like relationships, they don't quite follow SQL semantics,
in that the convention for an omitted reference is to write zero not
NULL.  Plus, we have some cases in which there are arrays each of whose
elements is supposed to be an FK reference; SQL has no way to model that.
So we can't create actual foreign key constraints to describe the
situation.  Nonetheless, we can collect and use knowledge about these
relationships.

This patch therefore adds annotations to the catalog header files to
declare foreign-key relationships.  (The BKI_LOOKUP annotations cover
simple cases, but we weren't previously distinguishing which such
columns are allowed to contain zeroes; we also need new markings for
multi-column FK references.)  Then, Catalog.pm and genbki.pl are
taught to collect this information into a table in a new generated
header "system_fk_info.h".  The only user of that at the moment is
a new SQL function pg_get_catalog_foreign_keys(), which exposes the
table to SQL.  The oidjoins regression test is rewritten to use
pg_get_catalog_foreign_keys() to find out which columns to check.
Aside from removing the need for manual maintenance of that test
script, this allows it to cover numerous relationships that were not
checked by the old implementation based on findoidjoins.  (As of this
commit, 217 relationships are checked by the test, versus 181 before.)

Discussion: https://postgr.es/m/3240355.1612129197@sss.pgh.pa.us

Not all OID-reference columns that can contain zeroes (indicating
"no reference") were explicitly marked in catalogs.sgml.  Fix that,
and try to make the style a little more consistent while at it ---
for example, consistently write "zero" not "0" for these cases.

Joel Jacobson and Tom Lane

Discussion: https://postgr.es/m/4ed9a372-7bf9-479a-926c-ae8e774717a8@www.fastmail.com

This left gaps in the internal statement numbering, which is not
terribly harmful (else we'd have noticed sooner), but it's not
great either.

Oversight in bbd5c207; backpatch to v12 where that came in.

Pavel Stehule

Discussion: https://postgr.es/m/CAFj8pRDXyQaJmpotNTQVc-t-WxdWZC35V2PnmwOaV1-taidFWA@mail.gmail.com

The ExecutorEnd hook is invoked in a context that could be quite
long-lived, not the executor's own per-query context as I think
we were sort of assuming.  Thus, any cruft generated while producing
the EXPLAIN output could accumulate over multiple queries.  This can
result in spectacular leakage if log_nested_statements is on, and
even without that I'm surprised nobody complained before.

To fix, just switch into the executor's context so that anything we
allocate will be released when standard_ExecutorEnd frees the executor
state.  We might as well nuke the code's retail pfree of the explain
output string, too; that's laughably inadequate to the need.

Japin Li, per report from Jeff Janes.  This bug is old, so
back-patch to all supported branches.

Discussion: https://postgr.es/m/CAMkU=1wCVtbeRn0s9gt12KwQ7PLXovbpM8eg25SYocKW3BT4hg@mail.gmail.com

The prototype calls the second argument of
pgstat_progress_update_multi_param() "index", and some callers name
their local variable that way.  But when the surrounding code deals
with index relations, this is confusing, and in at least one case
shadowed another variable that is referring to an index relation.
Adjust those call sites to have clearer local variable naming, similar
to existing callers in indexcmds.c.

The initial tablesync done by logical replication used a query to fetch
the information of a relation's columns that included atttypmod, but it
was left unused.  This was added by 7c4f5240.

Author: Euler Taveira
Reviewed-by: Önder Kalacı, Amit Langote, Japin Li
Discussion: https://postgr.es/m/CAHE3wggb715X+mK_DitLXF25B=jE6xyNCH4YOwM860JR7HarGQ@mail.gmail.com

Writing unnecessary '.*' at start and end of a POSIX regex doesn't
do much except confuse the reader about whether that might be
necessary after all.  Make the examples in table 9.16 a tad more
realistic, and try to turn the next group of examples into something
self-contained.

Per gripe from rmzgrimes.  Back-patch to v13 because it's easy.

Discussion: https://postgr.es/m/161215841824.14653.8969016349304314299@wrigleys.postgresql.org

It turns out that the calculation of [Merge]AppendPath.partitioned_rels
in allpaths.c is faulty and sometimes omits relevant non-leaf partitions,
allowing an assertion added by commit a929e17e to trigger.  Rather
than fix that, it seems better to get rid of those fields altogether.
We don't really need the info until create_plan time, and calculating
it once for the selected plan should be cheaper than calculating it
for each append path we consider.

The preceding two commits did away with all use of the partitioned_rels
values; this commit just mechanically removes the fields and the code
that calculated them.

Discussion: https://postgr.es/m/87sg8tqhsl.fsf@aurora.ydns.eu
Discussion: https://postgr.es/m/CAJKUy5gCXDSmFs2c=R+VGgn7FiYcLCsEFEuDNNLGfoha=pBE_g@mail.gmail.com

It turns out that the calculation of [Merge]AppendPath.partitioned_rels
in allpaths.c is faulty and sometimes omits relevant non-leaf partitions,
allowing an assertion added by commit a929e17e to trigger.  Rather
than fix that, it seems better to get rid of those fields altogether.
We don't really need the info until create_plan time, and calculating
it once for the selected plan should be cheaper than calculating it
for each append path we consider.

This patch undoes a couple of very minor uses of the partitioned_rels
values.

createplan.c was testing for nil-ness to optimize away the preparatory
work for make_partition_pruneinfo().  That is worth doing if the check
is nigh free, but it's not worth going to any great lengths to avoid.

create_append_path() was testing for nil-ness as part of deciding how
to set up ParamPathInfo for an AppendPath.  I replaced that with a
check for the appendrel's parent rel being partitioned.  That's not
quite the same thing but should cover most cases.  If we note any
interesting loss of optimizations, we can dumb this down to just
always use the more expensive method when the parent is a baserel.

Discussion: https://postgr.es/m/87sg8tqhsl.fsf@aurora.ydns.eu
Discussion: https://postgr.es/m/CAJKUy5gCXDSmFs2c=R+VGgn7FiYcLCsEFEuDNNLGfoha=pBE_g@mail.gmail.com

It turns out that the calculation of [Merge]AppendPath.partitioned_rels
in allpaths.c is faulty and sometimes omits relevant non-leaf partitions,
allowing an assertion added by commit a929e17e to trigger.  Rather
than fix that, it seems better to get rid of those fields altogether.
We don't really need the info until create_plan time, and calculating
it once for the selected plan should be cheaper than calculating it
for each append path we consider.

As a first step, teach make_partition_pruneinfo to collect the relevant
partitioned tables for itself.  It's not hard to do so by traversing
from child tables up to parents using the AppendRelInfo links.

While here, make some minor stylistic improvements; mainly, don't use
the "Relids" alias for bitmapsets that are not identities of any
relation considered by the planner.  Try to document the logic better,
too.

No backpatch, as there does not seem to be a live problem before
a929e17e.  Also no new regression test; the code where the bug
was will be gone at the end of this patch series, so it seems a
bit pointless to memorialize the issue.

Tom Lane and David Rowley, per reports from Andreas Seltenreich
and Jaime Casanova.

Discussion: https://postgr.es/m/87sg8tqhsl.fsf@aurora.ydns.eu
Discussion: https://postgr.es/m/CAJKUy5gCXDSmFs2c=R+VGgn7FiYcLCsEFEuDNNLGfoha=pBE_g@mail.gmail.com

This adds the SQL standard feature that adds the SEARCH and CYCLE
clauses to recursive queries to be able to do produce breadth- or
depth-first search orders and detect cycles.  These clauses can be
rewritten into queries using existing syntax, and that is what this
patch does in the rewriter.
Reviewed-by: Vik Fearing <vik@postgresfriends.org>
Reviewed-by: Pavel Stehule <pavel.stehule@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/db80ceee-6f97-9b4a-8ee8-3ba0c58e5be2@2ndquadrant.com

Current code allocates memory for JsonbValue, but it could be placed locally.

This is a replacement for the existing --with-openssl, extending the
logic to make easier the addition of new SSL libraries.  The grammar is
chosen to be similar to --with-uuid, where multiple values can be
chosen, with "openssl" as the only supported value for now.

The original switch, --with-openssl, is kept for compatibility.

Author: Daniel Gustafsson, Michael Paquier
Reviewed-by: Jacob Champion
Discussion: https://postgr.es/m/FAB21FC8-0F62-434F-AA78-6BD9336D630A@yesql.se

On machines where sizeof(Datum) > sizeof(Oid) (that is, any 64-bit
platform), the previous coding would compute a misaligned
workspace->index pointer if nupper is odd.  Architectures where
misaligned access is a hard no-no would then fail.  This appears
to explain why thorntail is unhappy but other buildfarm members
are not.

During the jsonb subscripting assignment, the provided path might assume an
object or an array where the source jsonb has a scalar value.  Initial
subscripting assignment logic will skip such an update operation with no
message shown.  This commit makes it throw an error to indicate this type
of situation.

Discussion: https://postgr.es/m/CA%2Bq6zcV8qvGcDXurwwgUbwACV86Th7G80pnubg42e-p9gsSf%3Dg%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcX3mdxGCgdThzuySwH-ApyHHM-G4oB1R0fn0j2hZqqkLQ%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcVDuGBv%3DM0FqBYX8DPebS3F_0KQ6OVFobGJPM507_SZ_w%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcVovR%2BXY4mfk-7oNk-rF91gH0PebnNfuUjuuDsyHjOcVA%40mail.gmail.com
Author: Dmitry Dolgov
Reviewed-by: Tom Lane, Arthur Zakirov, Pavel Stehule, Dian M Fay
Reviewed-by: Andrew Dunstan, Chapman Flack, Merlin Moncure, Peter Geoghegan
Reviewed-by: Alvaro Herrera, Jim Nasby, Josh Berkus, Victor Wagner
Reviewed-by: Aleksander Alekseev, Robert Haas, Oleg Bartunov

This commit introduces two new flags for jsonb assignment:

* JB_PATH_FILL_GAPS: Appending array elements on the specified position, gaps
  are filled with nulls (similar to the JavaScript behavior).  This mode also
  instructs to   create the whole path in a jsonb object if some part of the
  path (more than just the last element) is not present.

* JB_PATH_CONSISTENT_POSITION: Assigning keeps array positions consistent by
  preventing prepending of elements.

Both flags are used only in jsonb subscripting assignment.

Initially proposed by Nikita Glukhov based on polymorphic subscripting
patch, but transformed into an independent change.

Discussion: https://postgr.es/m/CA%2Bq6zcV8qvGcDXurwwgUbwACV86Th7G80pnubg42e-p9gsSf%3Dg%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcX3mdxGCgdThzuySwH-ApyHHM-G4oB1R0fn0j2hZqqkLQ%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcVDuGBv%3DM0FqBYX8DPebS3F_0KQ6OVFobGJPM507_SZ_w%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcVovR%2BXY4mfk-7oNk-rF91gH0PebnNfuUjuuDsyHjOcVA%40mail.gmail.com
Author: Dmitry Dolgov
Reviewed-by: Tom Lane, Arthur Zakirov, Pavel Stehule, Dian M Fay
Reviewed-by: Andrew Dunstan, Chapman Flack, Merlin Moncure, Peter Geoghegan
Reviewed-by: Alvaro Herrera, Jim Nasby, Josh Berkus, Victor Wagner
Reviewed-by: Aleksander Alekseev, Robert Haas, Oleg Bartunov

Subscripting for jsonb does not support slices, does not have a limit for the
number of subscripts, and an assignment expects a replace value to have jsonb
type.  There is also one functional difference between assignment via
subscripting and assignment via jsonb_set().  When an original jsonb container
is NULL, the subscripting replaces it with an empty jsonb and proceeds with
an assignment.

For the sake of code reuse, we rearrange some parts of jsonb functionality
to allow the usage of the same functions for jsonb_set and assign subscripting
operation.

The original idea belongs to Oleg Bartunov.

Catversion is bumped.

Discussion: https://postgr.es/m/CA%2Bq6zcV8qvGcDXurwwgUbwACV86Th7G80pnubg42e-p9gsSf%3Dg%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcX3mdxGCgdThzuySwH-ApyHHM-G4oB1R0fn0j2hZqqkLQ%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcVDuGBv%3DM0FqBYX8DPebS3F_0KQ6OVFobGJPM507_SZ_w%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcVovR%2BXY4mfk-7oNk-rF91gH0PebnNfuUjuuDsyHjOcVA%40mail.gmail.com
Author: Dmitry Dolgov
Reviewed-by: Tom Lane, Arthur Zakirov, Pavel Stehule, Dian M Fay
Reviewed-by: Andrew Dunstan, Chapman Flack, Merlin Moncure, Peter Geoghegan
Reviewed-by: Alvaro Herrera, Jim Nasby, Josh Berkus, Victor Wagner
Reviewed-by: Aleksander Alekseev, Robert Haas, Oleg Bartunov

The latestRemovedXid values used by nbtree deletion operations are
determined by _bt_delitems_delete()'s caller, so there is no reason to
pass a separate heapRel argument.

Oversight in commit d168b666.

When to_tsquery() or websearch_to_tsquery() meet a complex morph containing
multiple words residing adjacent position, these words are connected
with OP_AND operator.  That leads to surprising results.  For instace,
both websearch_to_tsquery('"pg_class pg"') and to_tsquery('pg_class <-> pg')
produce '( pg & class ) <-> pg' tsquery.  This tsquery requires
'pg' and 'class' words to reside on the same position and doesn't match
to to_tsvector('pg_class pg').  It appears to be ridiculous behavior, which
needs to be fixed.

This commit makes to_tsquery() or websearch_to_tsquery() connect words
residing adjacent position with OP_PHRASE.  Therefore, now those words are
normally chained with other OP_PHRASE operator.  The examples of above now
produces 'pg <-> class <-> pg' tsquery, which matches to
to_tsvector('pg_class pg').

Another effect of this commit is that complex morph word positions now need to
match the tsvector even if there is no surrounding OP_PHRASE.  This behavior
change generally looks like an improvement but making this commit not
backpatchable.

Reported-by: Barry Pederson
Bug: #16592
Discussion: https://postgr.es/m/16592-70b110ff9731c07d@postgresql.org
Discussion: https://postgr.es/m/CAPpHfdv0EzVhf6CWfB1_TTZqXV_2Sn-jSY3zSd7ePH%3D-%2B1V2DQ%40mail.gmail.com
Author: Alexander Korotkov
Reviewed-by: Tom Lane, Neil Chen

For those system catalogs that have a unique indexes, make a primary
key and unique constraint, using ALTER TABLE ... PRIMARY KEY/UNIQUE
USING INDEX.

This can be helpful for GUI tools that look for a primary key, and it
might in the future allow declaring foreign keys, for making schema
diagrams.

The constraint creation statements are automatically created by
genbki.pl from DECLARE_UNIQUE_INDEX directives.  To specify which one
of the available unique indexes is the primary key, use the new
directive DECLARE_UNIQUE_INDEX_PKEY instead.  By convention, we
usually make a catalog's OID column its primary key, if it has one.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/dc5f44d9-5ec1-a596-0251-dadadcdede98@2ndquadrant.com

The documentation as well as source code comments weren't entirely
clear whether SELECT INTO was truly deprecated (thus in theory
destined to be removed eventually), or just a less recommended
variant.  After discussion, it appears that other implementations also
use SELECT INTO in direct SQL in a way similar to PostgreSQL, so it
seems worth keeping it for compatibility.  Update the language in the
documentation to that effect.

Discussion: https://www.postgresql.org/message-id/flat/96dc0df3-e13a-a85d-d045-d6e2c85218da%40enterprisedb.com

The SQL standard allows a GRANTED BY clause on GRANT and
REVOKE (privilege) statements that can specify CURRENT_USER or
CURRENT_ROLE.  In PostgreSQL, both of these are the default behavior.
Since we already have all the parsing support for this for the
GRANT (role) statement, we might as well add basic support for this
for the privilege variant as well.  This allows us to check off SQL
feature T332.  In the future, perhaps more interesting things could be
done with this, too.
Reviewed-by: Simon Riggs <simon@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/f2feac44-b4c5-f38f-3699-2851d6a76dc9@2ndquadrant.com

Given a permanent relation rewritten in the current transaction, the
old_snapshot_threshold mechanism assumed the relation had never been
subject to early pruning.  Hence, a query could fail to report "snapshot
too old" when the rewrite followed an early truncation.  ALTER TABLE SET
TABLESPACE is probably the only rewrite mechanism capable of exposing
this bug.  REINDEX sets indcheckxmin, avoiding the problem.  CLUSTER has
zeroed page LSNs since before old_snapshot_threshold existed, so
old_snapshot_threshold has never cooperated with it.  ALTER TABLE
... SET DATA TYPE makes the table look empty to every past snapshot,
which is strictly worse.  Back-patch to v13, where commit
c6b92041 broke this.

Kyotaro Horiguchi and Noah Misch

Discussion: https://postgr.es/m/20210113.160705.2225256954956139776.horikyota.ntt@gmail.com

CREATE PUBLICATION has failed spuriously when applied to a permanent
relation created or rewritten in the current transaction.  Make the same
change to another site having the same semantic intent; the second
instance has no user-visible consequences.  Back-patch to v13, where
commit c6b92041 broke this.

Kyotaro Horiguchi

Discussion: https://postgr.es/m/20210113.160705.2225256954956139776.horikyota.ntt@gmail.com

In a cluster having used CREATE INDEX CONCURRENTLY while having enabled
prepared transactions, queries that use the resulting index can silently
fail to find rows.  Fix this for future CREATE INDEX CONCURRENTLY by
making it wait for prepared transactions like it waits for ordinary
transactions.  This expands the VirtualTransactionId structure domain to
admit prepared transactions.  It may be necessary to reindex to recover
from past occurrences.  Back-patch to 9.5 (all supported versions).

Andrey Borodin, reviewed (in earlier versions) by Tom Lane and Michael
Paquier.

Discussion: https://postgr.es/m/2E712143-97F7-4890-B470-4A35142ABC82@yandex-team.ru

The regression tests added in commits 708d165d and 411ae649 caused
buildfarm failures when  CLOBBER_CACHE_ALWAYS was enabled.
This commit stabilizes those tests.

The foreign server connections established by postgres_fdw behaves
differently depending on whether CLOBBER_CACHE_ALWAYS is enabled or not.
If it's not enabled, those connections are cached. On the other hand,
if it's enabled, when the connections are established outside transaction
block, they are not cached (i.e., they are immediately closed at the end of
query that established them). So the subsequent postgres_fdw_get_connections()
cannot list those connections and postgres_fdw_disconnect() cannot close them
(because they are already closed).

When the connections are established inside transaction block, they are
cached whether CLOBBER_CACHE_ALWAYS was enabled or not. But if it's enabled,
they are immediately marked as invalid, otherwise not. This causes the
subsequent postgres_fdw_get_connections() to return different result in
"valid" column depending on whether CLOBBER_CACHE_ALWAYS was enabled or not.

This commit prevents the above differences of behavior from
affecting the regression tests.

Per buildfarm failure on trilobite.

Original patch by Bharath Rupireddy. I (Fujii Masao) extracted
the regression test fix from that and revised it a bit.

Reported-by: Tom Lane
Author: Bharath Rupireddy
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/2688508.1611865371@sss.pgh.pa.us

The corresponding functions set_config and current_setting were
mostly not hyperlinked.  Clarify their descriptions a tad, too.

Discussion: https://postgr.es/m/161183356250.4077.687338658090583892@wrigleys.postgresql.org

When the .** jsonpath accessor handles the array, it selects both array and
each of its elements.  When using lax mode, subsequent accessors automatically
unwrap arrays.  So, the content of each array element may be selected twice.

Even though this behavior is counterintuitive, it's correct because everything
works as designed.  This commit documents it.

Backpatch to 12 where the jsonpath language was introduced.

Reported-by: Thomas Kellerer
Bug: #16828
Discussion: https://postgr.es/m/16828-2b0229babfad2d8c%40postgresql.org
Discussion: https://postgr.es/m/CAPpHfdtS-nNidT%3DEqZbAYOPcnNOWh_sd6skVdu2CAQUGdvpT8Q%40mail.gmail.com
Author: Alexandex Korotkov, revised by Tom Lane
Reviewed-by: Alvaro Herrera, Thomas Kellerer, Tom Lane
Backpatch-through: 12

This documentation has been added in 98681675, so no backpatch is
needed.

Author: Justin Pryzby, Michael Paquier
Discussion: https://postgr.es/m/20201222041153.GK30237@telsasoft.com

4c9c359d, that introduced those two functions, has been overoptimistic on
the point that only ShareUpdateExclusiveLock would be required when
moving a relation to a new tablespace.  AccessExclusiveLock is a
requirement, but ShareUpdateExclusiveLock may be used under specific
conditions like REINDEX CONCURRENTLY where waits on past transactions
make the operation safe even with a lower-level lock.  The current code
does only the former, so update the existing comments to reflect that.

Once a REINDEX (TABLESPACE) is introduced, those comments would require
an extra refresh to mention their new use case.

While on it, fix an incorrect variable name.

Per discussion with Álvaro Herrera.

Discussion: https://postgr.es/m/20210127140741.GA14174@alvherre.pgsql

Following the removal of pg_standby, also remove the documentation
section that describes how to write your own "waiting restore_command"
along the same lines.

Discussion: https://postgr.es/m/20201029024412.GP5380%40telsasoft.comReviewed-by: Michael Paquier <michael@paquier.xyz>

pg_standby was useful more than a decade ago, but now it is obsolete.
It has been proposed that we retire it many times.  Now seems like a
good time to finally do it, because "waiting restore commands"
are incompatible with a proposed recovery prefetching feature.

Discussion: https://postgr.es/m/20201029024412.GP5380%40telsasoft.com
Author: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>

Per buildfarm and local experimentation, bleeding-edge gcc isn't
convinced that the MemSet in reorder_function_arguments() is safe.
Shut it up by adding an explicit check that pronargs isn't negative,
and by changing MemSet to memset.  (It appears that either change is
enough to quiet the warning at -O2, but let's do both to be sure.)

In trying to protect the user from inconsistent behavior, commit
487e9861 "Enable BEFORE row-level triggers for partitioned tables"
tried to prevent BEFORE UPDATE FOR EACH ROW triggers from moving the row
from one partition to another.  However, it turns out that the
restriction is wrong in two ways: first, it fails spuriously, preventing
valid situations from working, as in bug #16794; and second, they don't
protect from any misbehavior, because tuple routing would cope anyway.

Fix by removing that restriction.

We keep the same restriction on BEFORE INSERT FOR EACH ROW triggers,
though.  It is valid and useful there.  In the future we could remove it
by having tuple reroute work for inserts as it does for updates.

Backpatch to 13.

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reported-by: Phillip Menke <pg@pmenke.de>
Discussion: https://postgr.es/m/16794-350a655580fbb9ae@postgresql.org

perform_pruning_combine_step() was not taught about the number of
partition indexes used in hash partitioning; more embarrassingly,
get_matching_hash_bounds() also had it wrong.  These errors are masked
in the common case where all the partitions have the same modulus
and no partition is missing.  However, with missing or unequal-size
partitions, we could erroneously prune some partitions that need
to be scanned, leading to silently wrong query answers.

While a minimal-footprint fix for this could be to export
get_partition_bound_num_indexes and make the incorrect functions use it,
I'm of the opinion that that function should never have existed in the
first place.  It's not reasonable data structure design that
PartitionBoundInfoData lacks any explicit record of the length of
its indexes[] array.  Perhaps that was all right when it could always
be assumed equal to ndatums, but something should have been done about
it as soon as that stopped being true.  Putting in an explicit
"nindexes" field makes both partition_bounds_equal() and
partition_bounds_copy() simpler, safer, and faster than before,
and removes explicit knowledge of the number-of-partition-indexes
rules from some other places too.

This change also makes get_hash_partition_greatest_modulus obsolete.
I left that in place in case any external code uses it, but no core
code does anymore.

Per bug #16840 from Michał Albrycht.  Back-patch to v11 where the
hash partitioning code came in.  (In the back branches, add the new
field at the end of PartitionBoundInfoData to minimize ABI risks.)

Discussion: https://postgr.es/m/16840-571a22976f829ad4@postgresql.org

We had "short *mdy" in the extern declarations, but "short mdy[3]"
in the actual function definitions.  Per C99 these are equivalent,
but recent versions of gcc have started to issue warnings about
the inconsistency.  Clean it up before the warnings get any more
widespread.

Back-patch, in case anyone wants to build older PG versions with
bleeding-edge compilers.

Discussion: https://postgr.es/m/2401575.1611764534@sss.pgh.pa.us