Otherwise we risk "leaking" deleted pages by making them non-recyclable
indefinitely.  Commit 6655a729 did the same thing for deleted pages in
GiST indexes.  That work was used as a starting point here.

Stop storing an XID indicating the oldest bpto.xact across all deleted
though unrecycled pages in nbtree metapages.  There is no longer any
reason to care about that condition/the oldest XID.  It only ever made
sense when wraparound was something _bt_vacuum_needs_cleanup() had to
consider.

The btm_oldest_btpo_xact metapage field has been repurposed and renamed.
It is now btm_last_cleanup_num_delpages, which is used to remember how
many non-recycled deleted pages remain from the last VACUUM (in practice
its value is usually the precise number of pages that were _newly
deleted_ during the specific VACUUM operation that last set the field).

The general idea behind storing btm_last_cleanup_num_delpages is to use
it to give _some_ consideration to non-recycled deleted pages inside
_bt_vacuum_needs_cleanup() -- though never too much.  We only really
need to avoid leaving a truly excessive number of deleted pages in an
unrecycled state forever.  We only do this to cover certain narrow cases
where no other factor makes VACUUM do a full scan, and yet the index
continues to grow (and so actually misses out on recycling existing
deleted pages).

These metapage changes result in a clear user-visible benefit: We no
longer trigger full index scans during VACUUM operations solely due to
the presence of only 1 or 2 known deleted (though unrecycled) blocks
from a very large index.  All that matters now is keeping the costs and
benefits in balance over time.

Fix an issue that has been around since commit 857f9c36, which added the
"skip full scan of index" mechanism (i.e. the _bt_vacuum_needs_cleanup()
logic).  The accuracy of btm_last_cleanup_num_heap_tuples accidentally
hinged upon _when_ the source value gets stored.  We now always store
btm_last_cleanup_num_heap_tuples in btvacuumcleanup().  This fixes the
issue because IndexVacuumInfo.num_heap_tuples (the source field) is
expected to accurately indicate the state of the table _after_ the
VACUUM completes inside btvacuumcleanup().

A backpatchable fix cannot easily be extracted from this commit.  A
targeted fix for the issue will follow in a later commit, though that
won't happen today.

I (pgeoghegan) have chosen to remove any mention of deleted pages in the
documentation of the vacuum_cleanup_index_scale_factor GUC/param, since
the presence of deleted (though unrecycled) pages is no longer of much
concern to users.  The vacuum_cleanup_index_scale_factor description in
the docs now seems rather unclear in any case, and it should probably be
rewritten in the near future.  Perhaps some passing mention of page
deletion will be added back at the same time.

Bump XLOG_PAGE_MAGIC due to nbtree WAL records using full XIDs now.

Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/CAH2-WznpdHvujGUwYZ8sihX=d5u-tRYhi-F4wnV2uN2zHpMUXw@mail.gmail.com

Author: Sawada Masahiko
Reviewed-by: Amit Kapila
Discussion: https://postgr.es/m/CAD21AoA7ZEfsOXQ9HQqMv3QYGsEm2H5Wk5ic5S=mvzDf-3a3SA@mail.gmail.com

The portions fixing the documentation are backpatched where needed.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20210210235557.GQ20012@telsasoft.com
backpatch-through: 9.6

Don't quote type name placeholders.

This parameter description was previously confusing, telling that a
value of 0 disabled completely status updates.  This is not true as
there are cases where an update is sent while ignoring this parameter
value.  The documentation is improved to outline the difference of
treatment for scheduled status messages and when these are forced.

Reported-by: Dmitriy Kuzmin
Author: Michael Paquier
Reviewed-by: Euler Taveira
Discussion: https://postgr.es/m/161346024420.3455.1345266601055047937@wrigleys.postgresql.org

d2d8a229 introduced a new function generate_useful_gather_paths to
be used as a replacement for generate_gather_paths, but forgot to update
a couple of places that referenced the older function.

This is possibly not 100% complete (ref. create_ordered_paths), but it's
better than not changing anything.

Author: "Hou, Zhijie" <houzj.fnst@cn.fujitsu.com>
Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Discussion: https://postgr.es/m/4ce1d5116fe746a699a6d29858c6a39a@G08CNEXMBPEKD05.g08.fujitsu.local

Commit 866e24d4 added an assert that HEAP_XMAX_LOCK_ONLY and
HEAP_KEYS_UPDATED cannot appear together, on the faulty assumption that
the latter necessarily referred to an update and not a tuple lock; but
that's wrong, because SELECT FOR UPDATE can use precisely that
combination, as evidenced by the amcheck test case added here.

Remove the Assert(), and also patch amcheck's verify_heapam.c to not
complain if the combination is found.  Also, out of overabundance of
caution, update (across all branches) README.tuplock to be more explicit
about this.

Author: Julien Rouhaud <rjuju123@gmail.com>
Reviewed-by: Mahendra Singh Thalor <mahi6run@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Discussion: https://postgr.es/m/20210124061758.GA11756@nol

gcc 10 is smart enough to notice that control could reach this
"hasmatch[depth]" assignment with depth < 0, but not smart enough
to know that that would require a badly broken NFA graph.  Change
the assert() to a plain runtime test to shut it up.

Per report from Andres Freund.

Discussion: https://postgr.es/m/20210223173437.b3ywijygsy6q42gq@alap3.anarazel.de

As envisioned in commit c98763bf, it is possible for VACUUM to
ignore certain transactions that are executing CREATE INDEX CONCURRENTLY
and REINDEX CONCURRENTLY for the purposes of computing Xmin; that's
because we know those transactions are not going to examine any other
tables, and are not going to execute anything else in the same
transaction.  (Only operations on "safe" indexes can be ignored: those
on indexes that are neither partial nor expressional).

This is extremely useful in cases where CIC/RC can run for a very long
time, because that used to be a significant headache for concurrent
vacuuming of other tables.
Reviewed-by: Matthias van de Meent <boekewurm+postgres@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/20210115133858.GA18931@alvherre.pgsql

Add a macro LSN_FORMAT_ARGS for use in printf-style printing of LSNs.
Convert all applicable code to use it.
Reviewed-by: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://www.postgresql.org/message-id/flat/CAExHW5ub5NaTELZ3hJUCE6amuvqAtsSxc7O+uK7y4t9Rrk23cw@mail.gmail.com

We don't have anything to decode in a transaction if ReorderBufferTXN
doesn't exist by the time we decode the commit prepared. So don't create a
new ReorderBufferTXN here. This is an oversight in commit a271a1b5.

Reported-by: Markus Wanner
Discussion: https://postgr.es/m/dbec82e2-dbd7-95a2-c6b6-e488cbbdf853@bluegap.ch

The authentication failure error message wasn't distinguishing whether
it is a physical replication or logical replication connection failure and
was giving incomplete information on what led to failure in case of logical
replication connection.

Author: Paul Martinez and Amit Kapila
Reviewed-by: Euler Taveira and Amit Kapila
Discussion: https://postgr.es/m/CACqFVBYahrAi2OPdJfUA3YCvn3QMzzxZdw0ibSJ8wouWeDtiyQ@mail.gmail.com

Pavan Deolasee recently noted that a few of the
HeapTupleHeaderIndicatesMovedPartitions calls added by commit
5db6df0c are useless, since they are done after comparing t_self
with t_ctid.  But because t_self can never be set to the magical values
that indicate that the tuple moved partition, this can never succeed: if
the first test fails (so we know t_self equals t_ctid), necessarily the
second test will also fail.

So these checks can be removed and no harm is done.  There's no bug
here, just a code legibility issue.
Reported-by: Pavan Deolasee <pavan.deolasee@gmail.com>
Discussion: https://postgr.es/m/20200929164411.GA15497@alvherre.pgsql

Building the docs with STYLE=website referenced a stylesheet that long
longer exists on the website, since we changed it to use versioned
references.

To make it less likely for this to happen again, point to a single
stylesheet on the website which will in turn import the required one.
That puts the process entirely within the scope of the website
repository, so next time a version is switched that's the only place
changes have to be made, making them less likely to be missed.

Per (off-list) discussion with Peter Geoghegan and Jonathan Katz.

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/20210117215940.GE8560%40telsasoft.com

The code paths for three different OSes finished up with three different
ways of excluding C[.xxx] and POSIX from consideration.  Merge them.
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/20210117215940.GE8560%40telsasoft.com

The new name seems a bit more natural.

Discussion: https://postgr.es/m/20210117215940.GE8560%40telsasoft.com

Instead of an unsightly internal "cache lookup failed" message, just
return NULL for bad OIDs, as is the convention for other similar things.
Reported-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/20210117215940.GE8560%40telsasoft.com

Commit 46d6e5f5 added the atomic variable "waitStart" into PGPROC struct,
to store the time at which wait for lock acquisition started. Previously
this variable was initialized every time each backend started. Instead,
this commit makes postmaster initialize it at the startup, to ensure that
the variable should be initialized before any use of it.

This commit also moves the code to initialize "waitStart" variable for
prepare transaction, from TwoPhaseGetDummyProc() to MarkAsPreparingGuts().
Because MarkAsPreparingGuts() is more proper place to do that since
it initializes other PGPROC variables.

Author: Fujii Masao
Reviewed-by: Atsushi Torikoshi
Discussion: https://postgr.es/m/1df88660-6f08-cc6e-b7e2-f85296a2bdab@oss.nttdata.com

For the error message "every hash partition modulus must be a factor
of the next larger modulus", add a detail message that shows the
particular numbers and existing partition involved.  Also comment the
code more.
Reviewed-by: Amit Langote <amitlangote09@gmail.com>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Discussion: https://www.postgresql.org/message-id/flat/bb9d60b4-aadb-607a-1a9d-fdc3434dddcd%40enterprisedb.com

This commit changes one code path in REINDEX INDEX and one code path
in CREATE INDEX CONCURRENTLY to report the progress of each operation
using pgstat_progress_update_multi_param() rather than
multiple calls to pgstat_progress_update_param().  This has the
advantage to make the progress report more consistent to the end-user
without impacting the amount of information provided.

Author: Bharath Rupireddy
Discussion: https://postgr.es/m/CALj2ACV5zW7GxD8D_tyO==bcj6ZktQchEKWKPBOAGKiLhAQo=w@mail.gmail.com

Commit b09ff536 left behind some outdated advice in the long_desc field
of the GUC "effective_io_concurrency".  Remove it.

Back-patch to 13.
Reported-by: Andrew Gierth <andrew@tao11.riddles.org.uk>
Reviewed-by: Julien Rouhaud <rjuju123@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKGJyyWqFBxL9gEj-qtjBThGjhAOBE8GBnF8MUJOJ3vrfag%40mail.gmail.com

Coverity complained that functions in regexec.c might leak DFA
storage.  It's wrong, but this logic is confusing enough that it's
not so surprising Coverity couldn't make sense of it.  Rewrite
in hopes of making it more legible to humans as well as machines.

Brown-paper-bag bug in 08c0d6ad: I missed one place that needed
to guard against RAINBOW arc colors.  Remarkably, nothing noticed
the invalid array access except buildfarm member thorntail.

Thanks to Noah Misch for assistance with tracking this down.

Previously, each pair of capturing parentheses gave rise to a separate
subre tree node, whose only function was to identify that we ought to
capture the match details for this particular sub-expression.  In
most cases we don't really need that, since we can perfectly well
put a "capture this" annotation on the child node that does the real
matching work.  As with the two preceding commits, the main value
of this is to avoid generating and optimizing an NFA for a tree node
that's not really pulling its weight.

The chosen data representation only allows one capture annotation
per subre node.  In the legal-per-spec, but seemingly not very useful,
case where there are multiple capturing parens around the exact same
bit of the regex (i.e. "((xyz))"), wrap the child node in N-1 capture
nodes that act the same as before.  We could work harder at that but
I'll refrain, pending some evidence that such cases are worth troubling
over.

In passing, improve the comments in regex.h to say what all the
different re_info bits mean.  Some of them were pretty obvious
but others not so much, so reverse-engineer some documentation.

This is part of a patch series that in total reduces the regex engine's
runtime by about a factor of four on a large corpus of real-world regexes.

Patch by me, reviewed by Joel Jacobson

Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us

Instead of having left and right child links in subre structs,
have a single child link plus a sibling link.  Multiple children
of a tree node are now reached by chasing the sibling chain.

The beneficiary of this is alternation tree nodes.  A regular
expression with N (>1) branches is now represented by one alternation
node with N children, rather than a tree that includes N alternation
nodes as well as N children.  While the old representation didn't
really cost anything extra at execution time, it was pretty horrid
for compilation purposes, because each of the alternation nodes had
its own NFA, which we were too stupid not to separately optimize.
(To make matters worse, all of those NFAs described the entire
alternation pattern, not just the portion of it that one might
expect from the tree structure.)

We continue to require concatenation nodes to have exactly two
children.  This data structure is now prepared to support more,
but the executor's logic would need some careful redesign, and
it's not clear that a lot of benefit could be had.

This is part of a patch series that in total reduces the regex engine's
runtime by about a factor of four on a large corpus of real-world regexes.

Patch by me, reviewed by Joel Jacobson

Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us

The comment for parsebranch() claims that it avoids generating
unnecessary concatenation nodes in the "subre" tree, but it missed
some significant cases.  Once we've decided that a given atom is
"messy" and can't be bundled with the preceding atom(s) of the
current regex branch, parseqatom() always generated two new concat
nodes, one to concat the messy atom to what follows it in the branch,
and an upper node to concatenate the preceding part of the branch
to that one.  But one or both of these could be unnecessary, if the
messy atom is the first, last, or only one in the branch.  Improve
the code to suppress such useless concat nodes, along with the
no-op child nodes representing empty chunks of a branch.

Reducing the number of subre tree nodes offers significant savings
not only at execution but during compilation, because each subre node
has its own NFA that has to be separately optimized.  (Maybe someday
we'll figure out how to share the optimization work across multiple
tree nodes, but it doesn't look easy.)  Eliminating upper tree nodes
is especially useful because they tend to have larger NFAs.

This is part of a patch series that in total reduces the regex engine's
runtime by about a factor of four on a large corpus of real-world regexes.

Patch by me, reviewed by Joel Jacobson

Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us

This builds on the previous "rainbow" patch to detect NFAs that will
match any string, though possibly with constraints on the string length.
This definition is chosen to match constructs such as ".*", ".+", and
".{1,100}".  Recognizing such an NFA after the optimization pass is
fairly cheap, since we basically just have to verify that all arcs
are RAINBOW arcs and count the number of steps to the end state.
(Well, there's a bit of complication with pseudo-color arcs for string
boundary conditions, but not much.)

Once we have these markings, the regex executor functions longest(),
shortest(), and matchuntil() don't have to expend per-character work
to determine whether a given substring satisfies such an NFA; they
just need to check its length against the bounds.  Since some matching
problems require O(N) invocations of these functions, we've reduced
the runtime for an N-character string from O(N^2) to O(N).  Of course,
this is no help for non-matchall sub-patterns, but those usually have
constraints that allow us to avoid needing O(N) substring checks in the
first place.  It's precisely the unconstrained "match-all" cases that
cause the most headaches.

This is part of a patch series that in total reduces the regex engine's
runtime by about a factor of four on a large corpus of real-world regexes.

Patch by me, reviewed by Joel Jacobson

Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us

Some regular expression constructs, most notably the "." match-anything
metacharacter, produce a sheaf of parallel NFA arcs covering all
possible colors (that is, character equivalence classes).  We can make
a noticeable improvement in the space and time needed to process large
regexes by replacing such cases with a single arc bearing the special
color code "RAINBOW".  This requires only minor additional complication
in places such as pull() and push().

Callers of pg_reg_getoutarcs() must now be prepared for the possibility
of seeing a RAINBOW arc.  For the one known user, contrib/pg_trgm,
that's a net benefit since it cuts the number of arcs to be dealt with,
and the handling isn't any different than for other colors that contain
too many characters to be dealt with individually.

This is part of a patch series that in total reduces the regex engine's
runtime by about a factor of four on a large corpus of real-world regexes.

Patch by me, reviewed by Joel Jacobson

Discussion: https://postgr.es/m/1340281.1613018383@sss.pgh.pa.us

REINDEX has recently gained support for partitions, so it can be
confusing to see those fields not being set.  Making useful reports for
for such relations is more complicated than it looks with the current
set of columns available in pg_stat_progress_create_index, and this
touches equally REINDEX DATABASE/SYSTEM/SCHEMA.  This commit documents
that those two columns are not touched during a REINDEX.

Reported-by: Justin Pryzby
Discussion: https://postgr.es/m/20210216064214.GI28165@telsasoft.com

This inconsistency was showing up after an autoreconf.

Reported-by: Antonin Houska
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/47255.1613716807@antos

When ON_ERROR_ROLLBACK is enabled, psql releases a temporary savepoint
if it's idle in a valid transaction block after executing a query. But psql
doesn't do that after RELEASE or ROLLBACK is executed because a temporary
savepoint has already been destroyed in that case.

This commit changes psql's ON_ERROR_ROLLBACK so that it doesn't release
a temporary savepoint also when COMMIT AND CHAIN is executed. A temporary
savepoint doesn't need to be released in that case because
COMMIT AND CHAIN also destroys any savepoints defined within the transaction
to commit. Otherwise psql tries to release the savepoint that
COMMIT AND CHAIN has already destroyed and cause an error
"ERROR:  savepoint "pg_psql_temporary_savepoint" does not exist".

Back-patch to v12 where transaction chaining was added.

Reported-by: Arthur Nascimento
Author: Arthur Nascimento
Reviewed-by: Fujii Masao, Vik Fearing
Discussion: https://postgr.es/m/16867-3475744069228158@postgresql.org

This commit fixes COMMIT AND CHAIN command so that it starts new transaction
immediately even if savepoints are defined within the transaction to commit.
Previously COMMIT AND CHAIN command did not in that case because
commit 280a408b forgot to make CommitTransactionCommand() handle
a transaction chaining when the transaction state was TBLOCK_SUBCOMMIT.

Also this commit adds the regression test for COMMIT AND CHAIN command
when savepoints are defined.

Back-patch to v12 where transaction chaining was added.

Reported-by: Arthur Nascimento
Author: Fujii Masao
Reviewed-by: Arthur Nascimento, Vik Fearing
Discussion: https://postgr.es/m/16867-3475744069228158@postgresql.org

Update to snowball tag v2.1.0.  Major changes are new stemmers for
Armenian, Serbian, and Yiddish.

Consolidate discussion of how VACUUM places pages in the FSM for
recycling by adding a new section that comes after discussion of page
deletion.  This structure reflects the fact that page recycling is
explicitly decoupled from page deletion in Lanin & Shasha's paper.  Page
recycling in nbtree is an implementation of what the paper calls "the
drain technique".

This decoupling is an important concept for nbtree VACUUM.  Searchers
have to detect and recover from concurrent page deletions, but they will
never have to reason about concurrent page recycling.  Recycling can
almost always be thought of as a low level garbage collection operation
that asynchronously frees the physical space that backs a logical tree
node.  Almost all code need only concern itself with logical tree nodes.
(Note that "logical tree node" is not currently a term of art in the
nbtree code -- this all works implicitly.)

This is preparation for an upcoming patch that teaches nbtree VACUUM to
remember the details of pages that it deletes on the fly, in local
memory.  This enables the same VACUUM operation to consider placing its
own deleted pages in the FSM later on, when it reaches the end of
btvacuumscan().

While poking at the regex code, I happened to notice that the bug
squashed in commit afcc8772 had a sibling: next() failed to return
a specific value associated with the '}' token for a "\{m,n\}"
quantifier when parsing in basic RE mode.  Again, this could result
in treating the quantifier as non-greedy, which it never should be in
basic mode.  For that to happen, the last character before "\}" that
sets "nextvalue" would have to set it to zero, or it'd have to have
accidentally been zero from the start.  The failure can be provoked
repeatably with, for example, a bound ending in digit "0".

Like the previous patch, back-patch all the way.

Commit 2c8dd05d added the atomic variable writtenUpto into
walreceiver's shared memory information. It's initialized only
when walreceiver started up but could be read via pg_stat_wal_receiver
view anytime, i.e., even before it's initialized. In the server built
with --disable-atomics and --disable-spinlocks, this uninitialized
atomic variable read could cause "invalid spinlock number: 0" error.

This commit changed writtenUpto so that it's initialized at
the postmaster startup, to avoid the uninitialized variable read
via pg_stat_wal_receiver and fix the error.

Also this commit moved the read of writtenUpto after the release
of spinlock protecting walreceiver's shared variables. This is
necessary to prevent new spinlock from being taken by atomic
variable read while holding another spinlock, and to shorten
the spinlock duration. This change leads writtenUpto not to be
consistent with the other walreceiver's shared variables protected
by a spinlock. But this is OK because writtenUpto should not be
used for data integrity checks.

Back-patch to v13 where commit 2c8dd05d introduced the bug.

Author: Fujii Masao
Reviewed-by: Michael Paquier, Thomas Munro, Andres Freund
Discussion: https://postgr.es/m/7ef8708c-5b6b-edd3-2cf2-7783f1c7c175@oss.nttdata.com

Add test coverage for the following operations, which were previously
not tested at all:

bytea LIKE bytea (bytealike)
bytea NOT LIKE bytea (byteanlike)
ESCAPE clause for the above (like_escape_bytea)

also

name NOT ILIKE text (nameicnlike)

Discussion: https://www.postgresql.org/message-id/flat/4d13563a-2c8d-fd91-20d5-e71b7a4eaa87%40enterprisedb.com

Add another method to specify CRLs, hashed directory method, for both
server and client side.  This offers a means for server or libpq to
load only CRLs that are required to verify a certificate.  The CRL
directory is specifed by separate GUC variables or connection options
ssl_crl_dir and sslcrldir, alongside the existing ssl_crl_file and
sslcrl, so both methods can be used at the same time.

Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/20200731.173911.904649928639357911.horikyota.ntt@gmail.com