We .gitignore'd this junk, but we didn't actually remove it.

The original placement of this module in src/fe_utils/ is ill-considered,
because several src/common/ modules have dependencies on it, meaning that
libpgcommon and libpgfeutils now have mutual dependencies.  That makes it
pointless to have distinct libraries at all.  The intended design is that
libpgcommon is lower-level than libpgfeutils, so only dependencies from
the latter to the former are acceptable.

We already have the precedent that fe_memutils and a couple of other
modules in src/common/ are frontend-only, so it's not stretching anything
out of whack to treat logging.c as a frontend-only module in src/common/.
To the extent that such modules help provide a common frontend/backend
environment for the rest of common/ to use, it's a reasonable design.
(logging.c does not yet provide an ereport() emulation, but one can
dream.)

Hence, move these files over, and revert basically all of the build-system
changes made by commit cc8d4151.  There are no places that need to grow
new dependencies on libpgcommon, further reinforcing the idea that this
is the right solution.

Discussion: https://postgr.es/m/a912ffff-f6e4-778a-c86a-cf5c47a12933@2ndquadrant.com

The existence of these files became rather confusing with the
introduction of a widely-known logging.h header in commit cc8d4151.
(Indeed, there's already some duplicative #includes here, perhaps
betraying such confusion.)  The only thing left in them, after that
commit, is a progress-reporting function that's neither general-purpose
nor tied in any way to other logging infrastructure.  Hence, let's just
move that function to pg_rewind.c, and get rid of the separate files.

Discussion: https://postgr.es/m/3971.1557787914@sss.pgh.pa.us

SQL's regular-expression substring() function is defined to have a
pattern argument that's separated into three subpatterns by escape-
double-quote markers; the function result is the part of the input
matching the second subpattern.  The standard makes it clear that
if there is ambiguity about how to match the input to the subpatterns,
the first and third subpatterns should be taken to match the smallest
possible amount of text (i.e., they're "non greedy", in the terms of
our regex code).  We were not doing it that way: the first subpattern
would eat the largest possible amount of text, causing the function
result to be shorter than what the spec requires.

Fix that by attaching explicit greediness quantifiers to the
subpatterns.  (This depends on the regex fix in commit 8a29ed05;
before that, this didn't reliably change the regex engine's behavior.)

Also, by adding parentheses around each subpattern, we ensure that
"|" (OR) in the subpatterns behave sanely.  Previously, "|" in the
first or third subpatterns didn't work.

This patch also makes the function throw error if you write more than
two escape-double-quote markers, and do something sane if you write
just one, and document that behavior.  Previously, an odd number of
markers led to a confusing complaint about unbalanced parentheses,
while extra pairs of markers were just ignored.  (Note that the spec
requires exactly two markers, but we've historically allowed there
to be none, and this patch preserves the old behavior for that case.)

In passing, adjust some substring() test cases that didn't really
prove what they said they were testing for: they used patterns
that didn't match the data string, so that the output would be
NULL whether or not the function was really strict.

Although this is certainly a bug fix, changing the behavior in back
branches seems undesirable: applications could perhaps be depending on
the old behavior, since it's not obviously wrong unless you read the
spec very closely.  Hence, no back-patch.

Discussion: https://postgr.es/m/5bb27a41-350d-37bf-901e-9d26f5592dd0@charter.net

Previously, the code pointed the standard process-termination signals
to postgres.c's die().  That would typically result in an attempt to
execute a transaction abort, which is not possible in bootstrap mode,
leading to PANIC.  This choice seems to be a leftover from an old code
structure in which the same signal-assignment code was used for many
sorts of auxiliary processes, including interactive standalone
backends.  It's not very sensible for bootstrap mode, which has no
interest in either interactivity or continuing after an error.  We can
get better behavior with less effort by just letting normal process
termination happen, after which the parent initdb process will clean up.

This is basically cosmetic in any case, since initdb will react the
same way whether bootstrap dies on a signal or abort().  Given the
lack of previous complaints, I don't feel a need to back-patch,
even though the behavior is old.

Discussion: https://postgr.es/m/3850b11a.5121.16aaf827e4a.Coremail.thunder1@126.com

This is mainly a light renumbering to match the sections in the
standard.

Per previous convention (see
ace397e9), drop SQL:2008 and only keep
the latest two standards and SQL-92.

Note: SQL:2016-2 lists a large number of non-reserved keywords that
are really just information_schema column names related to new
features.  Those kinds of thing have not previously been listed as
keywords, and this was apparently done here by mistake, since these
keywords have been removed again in post-2016 working drafts.  So in
order to avoid bloating the keywords table unnecessarily, I have
omitted these erroneous keywords here.

Reported-by: Amit Langote

Discussion: https://postgr.es/m/b7954643-41ef-a174-479d-1f8d4834f40a@lab.ntt.co.jp

Reported-by: nickb@imap.cc

Discussion: https://postgr.es/m/6b3414e1-fcef-4ad9-b123-b3ab3702d3db@www.fastmail.com

As we descend the GiST tree during insertion, we modify any downlinks on
the way down to include the new tuple we're about to insert (if they don't
cover it already). Modifying an existing downlink might cause an internal
page to split, if the new downlink tuple is larger than the old one. If
that happens, we need to back up to the parent and re-choose a page to
insert to. We used to detect that situation, thanks to the NSN-LSN
interlock normally used to detect concurrent page splits, but that got
broken by commit 9155580f. With that commit, we now use a dummy constant
LSN value for every page during index build, so the LSN-NSN interlock no
longer works. I thought that was OK because there can't be any other
backends modifying the index during index build, but missed that the
insertion itself can modify the page we're inserting to. The consequence
was that we would sometimes insert the new tuple to an incorrect page, one
whose downlink doesn't cover the new tuple.

To fix, add a flag to the stack that keeps track of the state while
descending tree, to indicate that a page was split, and that we need to
retry the descend from the parent.

Thomas Munro first reported that the contrib/intarray regression test was
failing occasionally on the buildfarm after commit 9155580f. The failure
was intermittent, because the gistchoose() function is not deterministic,
and would only occasionally create the right circumstances for this bug to
cause the failure.

Patch by Anastasia Lubennikova, with some changes by me to make it work
correctly also when the internal page split also causes the "grandparent"
to be split.

Discussion: https://www.postgresql.org/message-id/CA%2BhUKGJRzLo7tZExWfSbwM3XuK7aAK7FhdBV0FLkbUG%2BW0v0zg%40mail.gmail.com

The conditions listed in this comment have changed several times, and at
some point the thing that the "if so" referred to was negated.

The text was OK up to 9.6. It was differently wrong in v10, v11 and
master, so fix in all those versions.

Reported-by: Justin Pryzby

Discussion: https://postgr.es/m/20190513174759.GE23251@telsasoft.com

Reported-by: Amit Langote

Discussion: https://postgr.es/m/d5267ae5-bd4a-3e96-c21b-56bfa9fec7e8@lab.ntt.co.jp

Reported-by: Fabien COELHO

Discussion: https://postgr.es/m/alpine.DEB.2.21.1905130839140.13487@lancre

Author: Stephen Amell
Discussion: https://postgr.es/m/539fa271-21b3-777e-a468-d96cffe9c768@gmail.com

The term "item pointer" should not be used to refer to ItemIdData
variables, since that is needlessly ambiguous.  Only
ItemPointerData/ItemPointer variables should be called item pointers.

To fix, establish the convention that ItemIdData variables should always
be referred to either as "item identifiers" or "line pointers".  The
term "item identifier" already predominates in docs and translatable
messages, and so should be the preferred alternative there.

Discussion: https://postgr.es/m/CAH2-Wz=c=MZQjUzde3o9+2PLAPuHTpVZPPdYxN=E4ndQ2--8ew@mail.gmail.com

An upcoming HEAD-only patch will standardize the terminology around
ItemIdData variables/line pointers, ending the practice of referring to
them as "item pointers".  Make the "Database Page Layout" docs
consistent with the new policy.  The term "item identifier" is already
used in the same section, so stick with that.

Discussion: https://postgr.es/m/CAH2-Wz=c=MZQjUzde3o9+2PLAPuHTpVZPPdYxN=E4ndQ2--8ew@mail.gmail.com
Backpatch: All supported branches.

Only hand-assigned type OIDs should be presumed to match across different
PG servers; those assigned during genbki.pl or during initdb are likely
to change due to addition or removal of unrelated objects.

This means that the cutoff should be FirstGenbkiObjectId (in HEAD)
or FirstBootstrapObjectId (before that), not FirstNormalObjectId.
Compare postgres_fdw's is_builtin() test.

It's likely that this error has no observable consequence in a
normally-functioning system, since ATM the only affected type OIDs are
system catalog rowtypes and information_schema types, which would not
typically be interesting for logical replication.  But you could
probably break it if you tried hard, so back-patch.

Discussion: https://postgr.es/m/15150.1557257111@sss.pgh.pa.us

The FirstNormalObjectId test here is a kluge that needs to go away,
but the only substitute we can think of is to add a column to pg_class,
which will take more work than can be handled right now.  Add some
commentary in the meanwhile.

Discussion: https://postgr.es/m/15150.1557257111@sss.pgh.pa.us

Commit 8fa30f90 reduced the elevel of a number of "can't happen"
_bt_split() errors from PANIC to ERROR.  At the same time, the new right
page buffer for the split could continue to be acquired well before the
critical section.  This was possible because it was relatively
straightforward to make sure that _bt_split() could not throw an error,
with a few specific exceptions.  The exceptional cases were safe because
they involved specific, well understood errors, making it possible to
consistently zero the right page before actually raising an error using
elog().  There was no danger of leaving around a junk page, provided
_bt_split() stuck to this coding rule.

Commit 8224de4f, which introduced INCLUDE indexes, added code to make
_bt_split() truncate away non-key attributes.  This happened at a point
that broke the rule around zeroing the right page in _bt_split().  If
truncation failed (perhaps due to palloc() failure), that would result
in an errant right page buffer with junk contents.  This could confuse
VACUUM when it attempted to delete the page, and should be avoided on
general principle.

To fix, reorganize _bt_split() so that truncation occurs before the new
right page buffer is even acquired.  A junk page/buffer will not be left
behind if _bt_nonkey_truncate()/_bt_truncate() raise an error.

Discussion: https://postgr.es/m/CAH2-WzkcWT_-NH7EeL=Az4efg0KCV+wArygW8zKB=+HoP=VWMw@mail.gmail.com
Backpatch: 11-, where INCLUDE indexes were introduced.

The comment implies that a 1 in the null bitmap indicates a null value,
but actually a 0 in the null bitmap indicates a null value. Try to
be more clear.

Patch by me; proposed wording reviewed by Alvaro Herrera and Tom Lane.

Discussion: http://postgr.es/m/CA+TgmobHOP8r6cG+UnsDFMrS30-m=jRrCBhgw-nFkn0k9QnFsg@mail.gmail.com

pgtls_read_pending is declared to return bool, but what the underlying
SSL_pending function returns is a count of available bytes.

This is actually somewhat harmless if we're using C99 bools, but in
the back branches it's a live bug: if the available-bytes count happened
to be a multiple of 256, it would get converted to a zero char value.
On machines where char is signed, counts of 128 and up could misbehave
as well.  The net effect is that when using SSL, libpq might block
waiting for data even though some has already been received.

Broken by careless refactoring in commit 4e86f1b1, so back-patch
to 9.5 where that came in.

Per bug #15802 from David Binderman.

Discussion: https://postgr.es/m/15802-f0911a97f0346526@postgresql.org

Reported-by: David Rowley

Discussion: https://postgr.es/m/CAKJS1f-ktEhmQ2zJQ1L1niuJ9KB8WPA-bE-AhGiFsSO6QASB_w@mail.gmail.com

Tighten section designations.

equalsJsonbScalarValue() uses a boolean as return type, however for one
code path -1 gets returned, which is confusing.  The origin of the
confusion is visibly that this code got copy-pasted from
compareJsonbScalarValue() since it has been introduced in d1d50bff.

No backpatch, as this is only cosmetic.

Author: Rikard Falkeborn
Discussion: https://postgr.es/m/CADRDgG7mJnek6HNW13f+LF6V=6gag9PM+P7H5dnyWZAv49aBGg@mail.gmail.com

A bounded quantifier with m = n = 1 might be thought a no-op.  But
according to our documentation (which traces back to Henry Spencer's
original man page) it still imposes greediness, or non-greediness in the
case of the non-greedy variant "{1,1}?", on whatever it's attached to.

This turns out not to work though, because parseqatom() optimizes away
the m = n = 1 case without regard for whether it's supposed to change
the greediness of the argument RE.

We can fix this by just not applying the optimization when the greediness
needs to change; the subsequent general cases handle it fine.

The three cases in which we can still apply the optimization are
(a) no quantifier, or quantifier does not impose a preference;
(b) atom has no greediness property, implying it cannot match a
variable amount of text anyway; or
(c) quantifier's greediness is same as atom's.
Note that in most cases where one of these applies, we'd have exited
earlier in the "not a messy case" fast path.  I think it's now only
possible to get to the optimization when the atom involves capturing
parentheses or a non-top-level backref.

Back-patch to all supported branches.  I'd ordinarily be hesitant to
put a subtle behavioral change into back branches, but in this case
it's very hard to see a reason why somebody would write "{1,1}?" unless
they're trying to get the documented change-of-greediness behavior.

Discussion: https://postgr.es/m/5bb27a41-350d-37bf-901e-9d26f5592dd0@charter.net

The function had been interpreting SQL_ASCII messages as UTF8, throwing
an error when they were invalid UTF8.  The new behavior is consistent
with pg_do_encoding_conversion().  This affects LOG_DESTINATION_STDERR
and LOG_DESTINATION_EVENTLOG, which will send untranslated bytes to
write() and ReportEventA().  On buildfarm member bowerbird, enabling
log_connections caused an error whenever the role name was not valid
UTF8.  Back-patch to 9.4 (all supported versions).

Discussion: https://postgr.es/m/20190512015615.GD1124997@rfd.leadboat.com

We long ago decided to design the shared PgBackendStatus data structure to
minimize the cost of writing status updates, which means that writers just
have to increment the st_changecount field twice.  That isn't hooked into
any sort of resource management mechanism, which means that if something
were to throw error between the two increments, the st_changecount field
would be left odd indefinitely.  That would cause readers to lock up.
Now, since it's also a bad idea to leave the field odd for longer than
absolutely necessary (because readers will spin while we have it set),
the expectation was that we'd treat these segments like spinlock critical
sections, with only short, more or less straight-line, code in them.

That was fine as originally designed, but commit 9029f4b3 broke it
by inserting a significant amount of non-straight-line code into
pgstat_bestart(), code that is very capable of throwing errors, not to
mention taking a significant amount of time during which readers will spin.
We have a report from Neeraj Kumar of readers actually locking up, which
I suspect was due to an encoding conversion error in X509_NAME_to_cstring,
though conceivably it was just a garden-variety OOM failure.

Subsequent commits have loaded even more dubious code into pgstat_bestart's
critical section (and commit fc70a4b0 deserves some kind of booby prize
for managing to miss the critical section entirely, although the negative
consequences seem minimal given that the PgBackendStatus entry should be
seen by readers as inactive at that point).

The right way to fix this mess seems to be to compute all these values
into a local copy of the process' PgBackendStatus struct, and then just
copy the data back within the critical section proper.  This plan can't
be implemented completely cleanly because of the struct's heavy reliance
on out-of-line strings, which we must initialize separately within the
critical section.  But still, the critical section is far smaller and
safer than it was before.

In hopes of forestalling future errors of the same ilk, rename the
macros for st_changecount management to make it more apparent that
the writer-side macros create a critical section.  And to prevent
the worst consequences if we nonetheless manage to mess it up anyway,
adjust those macros so that they really are a critical section, ie
they now bump CritSectionCount.  That doesn't add much overhead, and
it guarantees that if we do somehow throw an error while the counter
is odd, it will lead to PANIC and a database restart to reset shared
memory.

Back-patch to 9.5 where the problem was introduced.

In HEAD, also fix an oversight in commit b0b39f72: it failed to teach
pgstat_read_current_status to copy st_gssstatus data from shared memory to
local memory.  Hence, subsequent use of that data within the transaction
would potentially see changing data that it shouldn't see.

Discussion: https://postgr.es/m/CAPR3Wj5Z17=+eeyrn_ZDG3NQGYgMEOY6JV6Y-WRRhGgwc16U3Q@mail.gmail.com

I already added that to the incompatibility section as a separate item.

Reported-by: Peter Geoghegan

Reported-by: Tom Lane

Discussion: https://postgr.es/m/28209.1556556696@sss.pgh.pa.us

This is because of the new tid in the index entry.

Reported-by: Peter Geoghegan

Reported-by: Andrew Gierth

Discussion: https://postgr.es/m/87r295hjur.fsf@news-spur.riddles.org.uk

The buildfarm client uses TEMP_CONFIG to implement its extra_config
setting.  Except for stats_temp_directory, extra_config now applies to
TAP suites; extra_config values seen in the past month are compatible
with this.  Back-patch to 9.6, where PostgresNode was introduced, so the
buildfarm can rely on it sooner.

Reviewed by Andrew Dunstan and Tom Lane.

Discussion: https://postgr.es/m/20181229021950.GA3302966@rfd.leadboat.com

When failing to reindex a table or an index, reindexdb would generate an
extra error message related to a database failure, which is misleading.

Backpatch all the way down, as this has been introduced by 85e9a5a0.

Discussion: https://postgr.es/m/CAOBaU_Yo61RwNO3cW6WVYWwH7EYMPuexhKqufb2nFGOdunbcHw@mail.gmail.com
Author: Julien Rouhaud
Reviewed-by: Daniel Gustafsson, Álvaro Herrera, Tom Lane, Michael
Paquier
Backpatch-through: 9.4