Whilst poking at nodeModifyTable.c, I chanced to notice that while
its calls to ExecBR*Triggers and ExecIR*Triggers are protected by
tests to see if there are any relevant triggers to fire, its calls
to ExecAR*Triggers are not; the latter functions do the equivalent
tests themselves.  This seems possibly reasonable given the more
complex conditions involved, but what's less reasonable is that
the ExecAR* functions aren't careful to do no work when there is
no work to be done.  ExecARInsertTriggers gets this right, but the
other two will both force creation of a slot that the query may
have no use for.  ExecARUpdateTriggers additionally performed a
usually-useless ExecClearTuple() on that slot.  This is probably
all pretty microscopic in real workloads, but a cycle shaved is a
cycle earned.

Seems the -1/singular output is used in the dblink regression tests.

Reported-by: Álvaro Herrera

Discussion: https://postgr.es/m/20210330231506.GA10666@alvherre.pgsql

The libpq_pipeline program recently introduced by commit acb7e4eb
is well equipped to test the PQtrace() functionality, so let's make it
do that.

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20210327192812.GA25115@alvherre.pgsql

Transform the PQtrace output format from its ancient (and mostly
useless) byte-level output format to a logical-message-level output,
making it much more usable.  This implementation allows the printing
code to be written (as it indeed was) by looking at the protocol
documentation, which gives more confidence that the three (docs, trace
code and actual code) actually match.

Author: 岩田 彩 (Aya Iwata) <iwata.aya@fujitsu.com>
Reviewed-by: 綱川 貴之 (Takayuki Tsunakawa) <tsunakawa.takay@fujitsu.com>
Reviewed-by: Kirk Jamison <k.jamison@fujitsu.com>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: 黒田 隼人 (Hayato Kuroda) <kuroda.hayato@fujitsu.com>
Reviewed-by: "Nagaura, Ryohei" <nagaura.ryohei@jp.fujitsu.com>
Reviewed-by: Ryo Matsumura <matsumura.ryo@fujitsu.com>
Reviewed-by: Greg Nancarrow <gregn4422@gmail.com>
Reviewed-by: Jim Doty <jdoty@pivotal.io>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/71E660EB361DF14299875B198D4CE5423DE3FBA4@g01jpexmbkw25

This outputs "-1 year", not "-1 years".

Reported-by: neverov.max@gmail.com

Bug: 16939

Discussion: https://postgr.es/m/16939-cceeb03fb72736ee@postgresql.org

This exercises a special case in the implementations of
date_part('epoch', timestamp[tz]) that was previously not tested.

Instead of using pg_usleep() in vacuum_delay_point(), use a WaitLatch.
This has the advantage that we will realize if the postmaster has been
killed since the last time we decided to sleep while vacuuming.

Reviewed-by: Thomas Munro
Discussion: https://postgr.es/m/CAFh8B=kcdk8k-Y21RfXPu5dX=bgPqJ8TC3p_qxR_ygdBS=JN5w@mail.gmail.com

As committed in bbe0a81d, pg_dump from a pre-v14 server effectively
acts as though you'd said --no-toast-compression.  I think the right
thing is for it to act as though default_toast_compression is set to
"pglz", instead, so that the tables' toast compression behavior is
preserved.  You can always get the other behavior, if you want that,
by giving the switch.

Discussion: https://postgr.es/m/1112852.1616609702@sss.pgh.pa.us

Here we add a new output parameter to estimate_num_groups() to allow it to
inform the caller of additional, possibly useful information about the
estimation.

The new output parameter is a struct that currently contains just a single
field with a set of flags.  This was done rather than having the flags as
an output parameter to allow future fields to be added without having to
change the signature of the function at a later date when we want to pass
back further information that might not be suitable to store in the flags
field.

It seems reasonable that one day in the future that the planner would want
to know more about the estimation. For example, how many individual sets
of statistics was the estimation generated from?  The planner may want to
take that into account if we ever want to consider risks as well as costs
when generating plans.

For now, there's only 1 flag we set in the flags field.  This is to
indicate if the estimation fell back on using the hard-coded constants in
any part of the estimation. Callers may like to change their behavior if
this is set, and this gives them the ability to do so.  Callers may pass
the flag pointer as NULL if they have no interest in obtaining any
additional information about the estimate.

We're not adding any actual usages of these flags here.  Some follow-up
commits will make use of this feature.  Additionally, we're also not
making any changes to add support for clauselist_selectivity() and
clauselist_selectivity_ext().  However, if this is required in the future
then the same struct being added here should be fine to use as a new
output argument for those functions too.

Author: David Rowley
Discussion: https://postgr.es/m/CAApHDvqQqpk=1W-G_ds7A9CsXX3BggWj_7okinzkLVhDubQzjA@mail.gmail.com

Some compilers are not aware that elog/ereport ERROR does not return.

Previously simplehash.h only exposed a method to perform a hash table
delete using the hash table key. This meant that the delete function had
to perform a hash lookup in order to find the entry to delete.  Here we
add a new function so that users of simplehash.h can perform a hash delete
directly using the entry pointer, thus saving the hash lookup.

An upcoming patch that uses simplehash.h already has performed the hash
lookup so already has the entry pointer.  This change will allow the
code in that patch to perform the hash delete without the code in
simplehash.h having to perform an additional hash lookup.

Author: David Rowley
Reviewed-by: Andres Freund
Discussion: https://postgr.es/m/CAApHDvqFLXXge153WmPsjke5VGOSt7Ez0yD0c7eBXLfmWxs3Kw@mail.gmail.com

The existing regression tests only tested the lower boundary of the
range supported by the timestamp and timestamptz types because "The
upper boundary differs between integer and float timestamps, so no
check".  Since this is obsolete, add similar tests for the upper
boundary.

Along with gid, this provides a different way to identify the transaction.
The users that use xid in some way to prepare the transactions can use it
to filter prepare transactions. The later commands COMMIT PREPARED or
ROLLBACK PREPARED carries both identifiers, providing an output plugin the
choice of what to use.

Author: Markus Wanner
Reviewed-by: Vignesh C, Amit Kapila
Discussion: https://postgr.es/m/ee280000-7355-c4dc-e47b-2436e7be959c@enterprisedb.com

Back-patch to all supported branches.

Author: Etsuro Fujita
Discussion: https://postgr.es/m/CAPmGK17DwzaSf%2BB71dhL2apXdtG-OmD6u2AL9Cq2ZmAR0%2BzapQ%40mail.gmail.com

We were never doing clearerr() on the output stream, which results in a
message being printed after each result once an EOF is seen:

could not print result table: Success

This message was added by commit b0343699 (in the pg13 era); before
that, the error indicator would never be examined.  So backpatch only
that far back, even though the actual bug (to wit: the fact that the
error indicator is never cleared) is older.

The design of the data structures which allow storage of the per-worker
memory during parallel seq scans were not ideal. The work done in
56788d21 required an additional data structure to allow workers to
remember the range of pages that had been allocated to them for
processing during a parallel seqscan.  That commit added a void pointer
field to TableScanDescData to allow heapam to store the per-worker
allocation information.  However putting the field there made very little
sense given that we have AM specific structs for that, e.g.
HeapScanDescData.

Here we remove the void pointer field from TableScanDescData and add a
dedicated field for this purpose to HeapScanDescData.

Previously we also allocated memory for this parallel per-worker data for
all scans, regardless if it was a parallel scan or not.  This was just a
wasted allocation for non-parallel scans, so here we make the allocation
conditional on the scan being parallel.

Also, add previously missing pfree() to free the per-worker data in
heap_endscan().

Reported-by: Andres Freund
Reviewed-by: Andres Freund
Discussion: https://postgr.es/m/20210317023101.anvejcfotwka6gaa@alap3.anarazel.de

Currently we only recognize the Common Name (CN) of a certificate's
subject to be matched against the user name. Thus certificates with
subjects '/OU=eng/CN=fred' and '/OU=sales/CN=fred' will have the same
connection rights. This patch provides an option to match the whole
Distinguished Name (DN) instead of just the CN. On any hba line using
client certificate identity, there is an option 'clientname' which can
have values of 'DN' or 'CN'. The default is 'CN', the current procedure.

The DN is matched against the RFC2253 formatted DN, which looks like
'CN=fred,OU=eng'.

This facility of probably best used in conjunction with an ident map.

Discussion: https://postgr.es/m/92e70110-9273-d93c-5913-0bccb6562740@dunslane.net

Reviewed-By: Michael Paquier, Daniel Gustafsson, Jacob Champion

Some tests for timestamp and timestamptz were in the date.sql test
file.  Move them to their appropriate files, or drop tests cases that
were already present there.

This allows decoding a string with Unicode escape sequences.  It is
similar to Unicode escape strings, but offers some more flexibility.

Author: Pavel Stehule <pavel.stehule@gmail.com>
Reviewed-by: Asif Rehman <asifr.rehman@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAFj8pRA5GnKT+gDVwbVRH2ep451H_myBt+NTz8RkYUARE9+qOQ@mail.gmail.com

After some tests relating to standard_conforming_strings behavior, the
value was not reset to the default value.  Therefore, the rest of the
tests in that file ran with the nondefault setting, which affected the
results of some tests.  For clarity, reset the value and run the rest
of the tests with the default setting again.

Assert that LP_UNUSED items have no storage.  If it's worth having
defensive code in non-assert builds then it's worth having an assertion
as well.

Here we aim to reduce duplicate work done by contain_volatile_functions()
by caching whether PathTargets and RestrictInfos contain any volatile
functions the first time contain_volatile_functions() is called for them.
Any future calls for these nodes just use the cached value rather than
going to the trouble of recursively checking the sub-node all over again.
Thanks to Tom Lane for the idea.

Any locations in the code which make changes to a PathTarget or
RestrictInfo which could change the outcome of the volatility check must
change the cached value back to VOLATILITY_UNKNOWN again.
contain_volatile_functions() is the only code in charge of setting the
cache value to either VOLATILITY_VOLATILE or VOLATILITY_NOVOLATILE.

Some existing code does benefit from this additional caching, however,
this change is mainly aimed at an upcoming patch that must check for
volatility during the join search.  Repeated volatility checks in that
case can become very expensive when the join search contains more than a
few relations.

Author: David Rowley
Discussion: https://postgr.es/m/3795226.1614059027@sss.pgh.pa.us

Commit c6763156 added an acronym reference for "TLS" but the definition
was never added.

Author: Daniel Gustafsson
Reviewed-by: Michael Paquier
Backpatch-through: 9.6
Discussion: https://postgr.es/m/27109504-82DB-41A8-8E63-C0498314F5B0@yesql.se

The tests used string concatenation to test statistics on expressions,
but that made the tests locale-dependent, e.g. because the ordering of
'11' and '1X' depends on the collation. This affected both the estimated
and actual row couts, breaking some of the tests.

Fixed by replacing the string concatenation with upper() function call,
so that the text values contain only digits.

Discussion: https://postgr.es/m/b650920b-2767-fbc3-c87a-cb8b5d693cbf%40enterprisedb.com

Allow defining extended statistics on expressions, not just just on
simple column references.  With this commit, expressions are supported
by all existing extended statistics kinds, improving the same types of
estimates. A simple example may look like this:

  CREATE TABLE t (a int);
  CREATE STATISTICS s ON mod(a,10), mod(a,20) FROM t;
  ANALYZE t;

The collected statistics are useful e.g. to estimate queries with those
expressions in WHERE or GROUP BY clauses:

  SELECT * FROM t WHERE mod(a,10) = 0 AND mod(a,20) = 0;

  SELECT 1 FROM t GROUP BY mod(a,10), mod(a,20);

This introduces new internal statistics kind 'e' (expressions) which is
built automatically when the statistics object definition includes any
expressions. This represents single-expression statistics, as if there
was an expression index (but without the index maintenance overhead).
The statistics is stored in pg_statistics_ext_data as an array of
composite types, which is possible thanks to 79f6a942.

CREATE STATISTICS allows building statistics on a single expression, in
which case in which case it's not possible to specify statistics kinds.

A new system view pg_stats_ext_exprs can be used to display expression
statistics, similarly to pg_stats and pg_stats_ext views.

ALTER TABLE ... ALTER COLUMN ... TYPE now treats indexes the same way it
treats indexes, i.e. it drops and recreates the statistics. This means
all statistics are reset, and we no longer try to preserve at least the
functional dependencies. This should not be a major issue in practice,
as the functional dependencies actually rely on per-column statistics,
which were always reset anyway.

Author: Tomas Vondra
Reviewed-by: Justin Pryzby, Dean Rasheed, Zhihong Yu
Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com

The regression tests of extended statistics were taking a fair amount of
time, due to using fairly large data sets with a couple thousand rows.
So far this was fine, but with tests for statistics on expressions the
duration would get a bit excessive.  So reduce the size of some of the
tests that will be used to test expressions, to keep the duration under
control.  Done in a separate commit before adding the statistics on
expressions, to make it clear which estimates are expected to change.

Author: Tomas Vondra
Discussion: https://postgr.es/m/ad7891d2-e90c-b446-9fe2-7419143847d7%40enterprisedb.com

When estimating the number of groups using extended statistics, the code
was discarding information about system attributes. This led to strange
situation that

    SELECT 1 FROM t GROUP BY ctid;

could have produced higher estimate (equal to pg_class.reltuples) than

    SELECT 1 FROM t GROUP BY a, b, ctid;

with extended statistics on (a,b). Fixed by retaining information about
the system attribute.

Backpatch all the way to 10, where extended statistics were introduced.

Author: Tomas Vondra
Backpatch-through: 10

Membership consists, implicitly, of the current database owner.  Expect
use in template databases.  Once pg_database_owner has rights within a
template, each owner of a database instantiated from that template will
exercise those rights.

Reviewed by John Naylor.

Discussion: https://postgr.es/m/20201228043148.GA1053024@rfd.leadboat.com

The next commit would have complicated two or three algorithms, so take
this opportunity to consolidate.  No functional changes.

Reviewed by John Naylor.

Discussion: https://postgr.es/m/20201228043148.GA1053024@rfd.leadboat.com

The deserialization failed to ensure correct alignment, as it assumed it
can simply point into the serialized value. The serialization however
ignores alignment and copies just the significant bytes in order to make
the result as small as possible. This caused failures on systems that
are sensitive to mialigned addresses, like sparc, or with address
sanitizer enabled.

Fixed by copying the serialized data to ensure proper alignment. While
at it, fix an issue with serialization on big endian machines, using the
same store_att_byval/fetch_att trick as extended statistics.

Discussion: https://postgr.es/0c8c3304-d3dd-5e29-d5ac-b50589a23c8c%40enterprisedb.com

Adds BRIN opclasses similar to the existing minmax, except that instead
of summarizing the page range into a single [min,max] range, the summary
consists of multiple ranges and/or points, allowing gaps. This allows
more efficient handling of data with poor correlation to physical
location within the table and/or outlier values, for which the regular
minmax opclassed tend to work poorly.

It's possible to specify the number of values kept for each page range,
either as a single point or an interval boundary.

  CREATE TABLE t (a int);
  CREATE INDEX ON t
   USING brin (a int4_minmax_multi_ops(values_per_range=16));

When building the summary, the values are combined into intervals with
the goal to minimize the "covering" (sum of interval lengths), using a
support procedure computing distance between two values.

Bump catversion, due to various catalog changes.

Author: Tomas Vondra <tomas.vondra@postgresql.org>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Sokolov Yura <y.sokolov@postgrespro.ru>
Reviewed-by: John Naylor <john.naylor@enterprisedb.com>
Discussion: https://postgr.es/m/c1138ead-7668-f0e1-0638-c3be3237e812@2ndquadrant.com
Discussion: https://postgr.es/m/5d78b774-7e9c-c94e-12cf-fef51cc89b1a%402ndquadrant.com

Adds a BRIN opclass using a Bloom filter to summarize the range. Indexes
using the new opclasses allow only equality queries (similar to hash
indexes), but that works fine for data like UUID, MAC addresses etc. for
which range queries are not very common. This also means the indexes
work for data that is not well correlated to physical location within
the table, or perhaps even entirely random (which is a common issue with
existing BRIN minmax opclasses).

It's possible to specify opclass parameters with the usual Bloom filter
parameters, i.e. the desired false-positive rate and the expected number
of distinct values per page range.

  CREATE TABLE t (a int);
  CREATE INDEX ON t
   USING brin (a int4_bloom_ops(false_positive_rate = 0.05,
                                n_distinct_per_range = 100));

The opclasses do not operate on the indexed values directly, but compute
a 32-bit hash first, and the Bloom filter is built on the hash value.
Collisions should not be a huge issue though, as the number of distinct
values in a page ranges is usually fairly small.

Bump catversion, due to various catalog changes.

Author: Tomas Vondra <tomas.vondra@postgresql.org>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Sokolov Yura <y.sokolov@postgrespro.ru>
Reviewed-by: Nico Williams <nico@cryptonector.com>
Reviewed-by: John Naylor <john.naylor@enterprisedb.com>
Discussion: https://postgr.es/m/c1138ead-7668-f0e1-0638-c3be3237e812@2ndquadrant.com
Discussion: https://postgr.es/m/5d78b774-7e9c-c94e-12cf-fef51cc89b1a%402ndquadrant.com

Commit a1c649d8 changed the signature of the BRIN consistent function
by adding a new required parameter.  Treating the parameter as optional,
which would make the change backwards incompatibile, was rejected with
the justification that there are few out-of-core extensions, so it's not
worth adding making the code more complex, and it's better to deal with
that in the extension.

But after further thought, that would be rather problematic, because
pg_upgrade simply dumps catalog contents and the same version of an
extension needs to work on both PostgreSQL versions. Supporting both
variants of the consistent function (with 3 or 4 arguments) makes that
possible.

The signature is not the only thing that changed, as commit 72ccf55c
moved handling of IS [NOT] NULL keys from the support procedures. But
this change is backward compatible - handling the keys in exension is
unnecessary, but harmless. The consistent function will do a bit of
unnecessary work, but it should be very cheap.

This also undoes most of the changes to the existing opclasses (minmax
and inclusion), making them use the old signature again. This should
make backpatching simpler.

Catversion bump, because of changes in pg_amproc.

Author: Tomas Vondra <tomas.vondra@postgresql.org>
Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Reviewed-by: Mark Dilger <hornschnorter@gmail.com>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Masahiko Sawada <masahiko.sawada@enterprisedb.com>
Reviewed-by: John Naylor <john.naylor@enterprisedb.com>
Discussion: https://postgr.es/m/c1138ead-7668-f0e1-0638-c3be3237e812@2ndquadrant.com

The BRIN minmax opclasses included amproc entries with mismatching left
and right types, but those happen to be unnecessary.  The opclasses only
need cross-type operators, not cross-type support procedures. Discovered
when trying to define equivalent BRIN operator families in an extension.

Catversion bump, because of pg_amproc changes.

Author: Tomas Vondra
Reviewed-by: Alvaro Herrera
Discussion: https://postgr.es/m/78c357ab-3395-8433-e7b3-b2cfcc9fdc23%40enterprisedb.com

Before, trying to compress a value for insertion into an expression
index would crash.

Dilip Kumar, with some editing by me. Report by Jaime Casanova.

Discussion: http://postgr.es/m/CAJKUy5gcs0zGOp6JXU2mMVdthYhuQpFk=S3V8DOKT=LZC1L36Q@mail.gmail.com

Allow a partition be detached from its partitioned table without
blocking concurrent queries, by running in two transactions and only
requiring ShareUpdateExclusive in the partitioned table.

Because it runs in two transactions, it cannot be used in a transaction
block.  This is the main reason to use dedicated syntax: so that users
can choose to use the original mode if they need it.  But also, it
doesn't work when a default partition exists (because an exclusive lock
would still need to be obtained on it, in order to change its partition
constraint.)

In case the second transaction is cancelled or a crash occurs, there's
ALTER TABLE .. DETACH PARTITION .. FINALIZE, which executes the final
steps.

The main trick to make this work is the addition of column
pg_inherits.inhdetachpending, initially false; can only be set true in
the first part of this command.  Once that is committed, concurrent
transactions that use a PartitionDirectory will include or ignore
partitions so marked: in optimizer they are ignored if the row is marked
committed for the snapshot; in executor they are always included.  As a
result, and because of the way PartitionDirectory caches partition
descriptors, queries that were planned before the detach will see the
rows in the detached partition and queries that are planned after the
detach, won't.

A CHECK constraint is created that duplicates the partition constraint.
This is probably not strictly necessary, and some users will prefer to
remove it afterwards, but if the partition is re-attached to a
partitioned table, the constraint needn't be rechecked.

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Amit Langote <amitlangote09@gmail.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql

On partition detach, we acquire a SHARE lock on all tables that
reference the partitioned table that we're detaching a partition from,
but failed to document this fact.  My oversight in commit f56f8f8d.
Repair.  Backpatch to 12.

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20210325180244.GA12738@alvherre.pgsql

The prior commit which introduced it was pretty squalid in terms of
code documentation, so add some comments.

Struct AlteredRelationInfo gains a new Relation member, to be used only
by Phase 2 (ATRewriteCatalogs); this allows ATExecCmd() subroutines open
and close the relation internally.

A future commit will use this facility to implement an ALTER TABLE
subcommand that closes and reopens the relation across transaction
boundaries.

(It is possible to keep the relation open past phase 2 to be used by
phase 3 instead of having to reopen it that point, but there are some
minor complications with that; it's not clear that there is much to be
won from doing that, though.)

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20200803234854.GA24158@alvherre.pgsql