jsonb_object_field_text and jsonb_array_element_text both contained
identical copies of this code, so extract that into new routine
JsonbValueAsText.  This can also be used in other places, to measurable
performance benefit: the jsonb_each() and jsonb_array_elements()
functions can use it for outputting text forms instead of their less
efficient current implementation (because we no longer need to build
intermediate a jsonb representation of each value).

Author: Nikita Glukhov
Discussion: https://postgr.es/m/7c417f90-f95f-247e-ba63-d95e39c0ad14@postgrespro.ru

Although the SQL/JSON tech report makes reference to ECMAScript which
allows both single- and double-quoted strings, all the rest of the
report speaks only of double-quoted string literals in jsonpaths.
That's more compatible with JSON itself; moreover single-quoted strings
are hard to use inside a jsonpath that is itself a single-quoted SQL
literal.  So guess that the intent is to allow only double-quoted
literals, and remove lexer support for single-quoted literals.
It'll be less painful to add this again later if we're wrong, than to
remove a shipped feature.

Also, adjust the lexer so that unrecognized backslash sequences are
treated as just meaning the escaped character, not as errors.  This
change has much better support in the standards, as JSON, JavaScript
and ECMAScript all make it plain that that's what's supposed to
happen.

Back-patch to v12.

Discussion: https://postgr.es/m/CAPpHfdvDci4iqNF9fhRkTqhe-5_8HmzeLt56drH%2B_Rv2rNRqfg@mail.gmail.com

This reverts commit bd7c95f0,
along with assorted follow-on fixes.  There are some questions
about the definition and implementation of that statement, and
we don't have time to resolve them before v13 release.  Rather
than ship the feature and then have backwards-compatibility
concerns constraining any redesign, let's remove it for now
and try again later.

Discussion: https://postgr.es/m/TY2PR01MB2443EC8286995378AEB7D9F8F5B10@TY2PR01MB2443.jpnprd01.prod.outlook.com

I (Álvaro) broke that in commit 6212276e -- forgot to set the
necessary flag.  Repair.

Author: Amit Langote
Discussion: https://postgr.es/m/CA+HiwqEaM2tV5awKhP1vSbgjQe_uXVU15Oi4sTgwgempwMiT8g@mail.gmail.com

f5f084fc has removed test because of its instability.  This commit provides
alternative test with determined ordering using extra ORDER BY expression.

Backpatch-through: 12

Reported-By: Kuntal Ghosh (off-list)
Backpatch-through: 9.4, like 82fa3ff8

6cae9d2c introduced test for NULL values in KNN SP-GiST.  This test relies on
undetermined ordering showing different results on various platforms.  This
commit removes that test.  Will be replaced with better test later.

Discussion: https://postgr.es/m/6d51305e1159241cabee132f7efc7eff%40xs4all.nl
Backpatch-through: 12

6cae9d2c has added an error in freeing old values in
index_store_float8_orderby_distances() function.  It looks for old value in
scan->xs_orderbynulls[i] after setting a new value there.
This commit fixes that.  Also it removes short-circuit in handling
distances == NULL situation.  Now distances == NULL will be treated the same
way as array with all null distances.  That is, previous values will be freed
if any.

Reported-by: Tom Lane, Nikita Glukhov
Discussion: https://postgr.es/m/CAPpHfdu2wcoAVAm3Ek66rP%3Duo_C-D84%2B%2Buf1VEcbyi_caBXWCA%40mail.gmail.com
Discussion: https://postgr.es/m/426580d3-a668-b9d1-7b8e-f74d1a6524e0%40postgrespro.ru
Backpatch-through: 12

This commit improves subject in two ways:

 * It removes ugliness of 02f90879, which stores distance values and null
   flags in two separate arrays after GISTSearchItem struct.  Instead we pack
   both distance value and null flag in IndexOrderByDistance struct.  Alignment
   overhead should be negligible, because we typically deal with at most few
   "col op const" expressions in ORDER BY clause.
 * It fixes handling of "col op NULL" expression in KNN-SP-GiST.  Now, these
   expression are not passed to support functions, which can't deal with them.
   Instead, NULL result is implicitly assumed.  It future we may decide to
   teach support functions to deal with NULL arguments, but current solution is
   bugfix suitable for backpatch.

Reported-by: Nikita Glukhov
Discussion: https://postgr.es/m/826f57ee-afc7-8977-c44c-6111d18b02ec%40postgrespro.ru
Author: Nikita Glukhov
Reviewed-by: Alexander Korotkov
Backpatch-through: 9.4

Provide some documentation about the differences between XQuery
regular expressions and those supported by Spencer's regex engine.
Since SQL now exposes XQuery regexps with the LIKE_REGEX operator,
I made this a standalone section designed to help somebody who
has to translate a LIKE_REGEX query to Postgres.  (Eventually we might
extend Spencer's engine to allow precise implementation of XQuery,
but not today.)

Reference that in the jsonpath docs, provide definitions of the
XQuery flag letters, and add a description of the JavaScript-inspired
string literal syntax used within jsonpath.  Also point out explicitly
that backslashes used within like_regex patterns will need to be doubled.

This also syncs the docs with the decision implemented in commit
d5b90cd6 to desupport XQuery's 'x' flag for now.

Jonathan Katz and Tom Lane

Discussion: https://postgr.es/m/CAPpHfdvDci4iqNF9fhRkTqhe-5_8HmzeLt56drH%2B_Rv2rNRqfg@mail.gmail.com

Make the error messages around GSSAPI encryption a bit clearer.  Tweak
some messages to avoid plural problems.

Also make a code change for clarity.  Using "conf" for "confidential"
is quite confusing.  Using "conf_state" is perhaps not much better but
that's what the GSSAPI documentation uses, so there is at least some
hope of understanding it.

Reported-by: Filip Rembiałkowski
Author: Filip Rembiałkowski
Backpatch-through: 12, where it was introduced
Discussion: https://postgr.es/m/CAP_rwwmSNy1=_82rwGe3-X4PjWqPSFXtzNf43DCtGzD7SazdXA@mail.gmail.com

The major version of ecpglib was changed in
bd7c95f0, apparently without
justification.  Revert this, since nothing has changed in this library
except some added functions.

Discussion: https://www.postgresql.org/message-id/flat/48ee4c56-e1df-b39d-2cad-c7d80b120eb5%402ndquadrant.com

This fixes an inconsistency with this parameter name not listed in the
command synopsis, and connection_name is the parameter name more
commonly used in the docs for ECPG commands.

Reported-by: Yusuke Egashita
Discussion: https://postgr.es/m/156870956796.1259.11456186889345212399@wrigleys.postgresql.org
Backpatch-through: 9.4

It's important users be able to know (without looking at the source code)
that running DDL or DDL-like commands can interrupt autovacuum which can
lead to a lot of dead tuples and hence slower database operations.

Reported-by: James Coleman
Author: James Coleman
Reviewed-by: Amit Kapila
Backpatch-through: 9.4
Discussion: https://postgr.es/m/CAAaqYe-XYyNwML1=f=gnd0qWg46PnvD=BDrCZ5-L94B887XVxQ@mail.gmail.com

After more discussion, the new function added by ddbd5d87 could have been
designed in a better way.  Based on an idea from Álvaro, instead of
returning one column which includes both the raw and combined flags, use
two columns, with one for the raw flags and one for the combined flags.

This also takes care of some issues with HEAP_LOCKED_UPGRADED and
HEAP_XMAX_IS_LOCKED_ONLY which are not really combined flags as they
depend on conditions defined by other raw bits, as mentioned by Amit.

While on it, fix an extra issue with combined flags.  A combined flag
was returned if at least one of its bits was set, but all its bits need
to be set to include it in the result.

Author: Michael Paquier
Reviewed-by: Álvaro Herrera, Amit Kapila
Discussion: https://postgr.es/m/20190913114950.GA3824@alvherre.pgsql

Fixup for previous commit: actually, the complete source for
testlibpq3.c appears in SGML docs, so we need to patch that also.
Go figure.

The sample output assumes non-standard-conforming interpretation of
backslashes in input literals, so the actual output didn't match.

Noticed while perusing another patch that touches this file.

Evidently this code is seldom checked, so I'm not going to bother
backpatching this fix.

Lack of quotes results in failure to run the test under older Solaris.

Author: Marina Polyakova, Victor Wagner
Discussion: https://postgr.es/m/feba89f89e8925b3535cb7d72b9e05e1@postgrespro.ru

smgrdounlinkfork() became dead code as the result of commit ece01aae,
but it was left in place just in case we want it someday. However no users
have appeared in 7 years, so it's time to remove this unused function.

Author: Kirk Jamison
Discussion: https://www.postgresql.org/message-id/D09B13F772D2274BB348A310EE3027C64E2067@g01jpexmbkw24

1. Commit 7086be6e should have documented the limitation that the direct
   modification is disabled when WCO constraints are present, but didn't,
   which is definitely my fault.  Update the documentation (Postgres 9.6
   onwards).

2. Commit fc22b662 should have documented the limitation that the direct
   modification is disabled when generated columns are defined, but
   didn't.  Update the documentation (Postgres 12 onwards).

Author: Etsuro Fujita
Discussion: https://postgr.es/m/CAPmGK14AYCPunLb6TRz1CQsW5Le01Z2ox8LSOKH0P-cOVDcQRA%40mail.gmail.com

Author: Mark G <markg735@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAEeOP_YFVeFjq4zDZLDQbLSRFxBiTpwBQHxCNgGd%2Bp5VztTXyQ%40mail.gmail.com

The SQL spec defers to XQuery to define what the option flags are
for LIKE_REGEX patterns.  XQuery says that:
* 's' allows the dot character to match newlines, which by
  default it will not;
* 'm' allows ^ and $ to match at newlines, not only at the
  start/end of the whole string.
Thus, these are *not* inverses as they are for the similarly-named
POSIX options, and neither one corresponds to the POSIX 'n' option.
Fortunately, Spencer's library does expose these two behaviors as
separately twiddlable flags, so we just have to fix the mapping from
JSP flag bits to REG flag bits.  I also chose to rename the symbol
for 's' to DOTALL, to make it clearer that it's not the inverse
of MLINE.

Also, XQuery says that if the 'q' flag "is used together with the m, s,
or x flag, that flag has no effect".  I read this as saying that 'q'
overrides the other flags; whoever wrote our code seems to have read
it backwards.

Lastly, while XQuery's 'x' flag is related to what Spencer's code
does for REG_EXPANDED, it's not the same or a subset.  It seems best
to treat XQuery's 'x' as unimplemented for now.  Maybe later we can
expand our regex code to offer 'x'-style parsing as a separate option.

While at it, refactor the jsonpath code so that (a) there's only
one copy of the flag transformation logic not two, and (b) the
processing of flags is independent of the order in which the flags
are written.

We need some documentation updates to go with this, but I'll
tackle that separately.

Back-patch to v12 where this code originated.

Discussion: https://postgr.es/m/CAPpHfdvDci4iqNF9fhRkTqhe-5_8HmzeLt56drH%2B_Rv2rNRqfg@mail.gmail.com
Reference: https://www.w3.org/TR/2017/REC-xpath-functions-31-20170321/#flags

We believe that the issues that this was working around have been
fixed in MinGW more than 5 years ago, so this isn't necessary anymore.

Discussion: https://www.postgresql.org/message-id/flat/20190719050830.GK1859%40paquier.xyz

SQL Standard 2016 defines SSSSS format pattern for seconds past midnight in
jsonpath .datetime() method and CAST (... FORMAT ...) SQL clause.  In our
datetime parsing engine we currently support it with SSSS name.

This commit adds SSSSS as an alias for SSSS.  Alias is added in favor of
upcoming jsonpath .datetime() method.  But it's also supported in to_date()/
to_timestamp() as positive side effect.

Discussion: https://postgr.es/m/CAPpHfdsZgYEra_PeCLGNoXOWYx6iU-S3wF8aX0ObQUcZU%2B4XTw%40mail.gmail.com
Author: Nikita Glukhov, Alexander Korotkov
Reviewed-by: Anastasia Lubennikova, Peter Eisentraut

SQL Standard 2016 defines FF1-FF9 format patters for fractions of seconds in
jsonpath .datetime() method and CAST (... FORMAT ...) SQL clause.  Parsing
engine of upcoming .datetime() method will be shared with to_date()/
to_timestamp().

This patch implements FF1-FF6 format patterns for upcoming jsonpath .datetime()
method.  to_date()/to_timestamp() functions will also get support of this
format patterns as positive side effect.  FF7-FF9 are not supported due to
lack of precision in our internal timestamp representation.

Extracted from original patch by Nikita Glukhov, Teodor Sigaev, Oleg Bartunov.
Heavily revised by me.

Discussion: https://postgr.es/m/fcc6fc6a-b497-f39a-923d-aa34d0c588e8%402ndQuadrant.com
Discussion: https://postgr.es/m/CAPpHfdsZgYEra_PeCLGNoXOWYx6iU-S3wF8aX0ObQUcZU%2B4XTw%40mail.gmail.com
Author: Nikita Glukhov, Teodor Sigaev, Oleg Bartunov, Alexander Korotkov
Reviewed-by: Anastasia Lubennikova, Peter Eisentraut

Noted by Coverity.  Typo in 27cc7cd2, so back-patch to v12
as that was.

Commit d7f8d26d added new tests to the stats_ext regression test that
included creating a view in the public schema, without realising that
the stats_ext test runs in the same parallel group as the rules test,
which makes doing that unsafe.

This led to intermittent failures of the rules test on the buildfarm,
although I wasn't able to reproduce that locally. Fix by creating the
view in a different schema.

Tomas Vondra and Dean Rasheed, report and diagnosis by Thomas Munro.

Discussion: https://postgr.es/m/CA+hUKGKX9hFZrYA7rQzAMRE07L4hziCc-nO_b3taJpiuKyLLxg@mail.gmail.com

This reverts commit e7ff5968.  It
defined pg_atomic_fetch_add_u32_impl() without defining
pg_atomic_compare_exchange_u32_impl(), which is incompatible with
src/include/port/atomics/fallback.h.  Per buildfarm member prairiedog.

Discussion: https://postgr.es/m/7517.1568470247@sss.pgh.pa.us

This is more like how we handle s_lock.h and arch-x86.h.  This does not
materially affect code generation for gcc 7.2.0 or xlc 13.1.3.

Reviewed by Tom Lane.

Discussion: https://postgr.es/m/20190831071157.GA3251746@rfd.leadboat.com

PostgreSQL has been unusable when built with xlc 13 and newer, which are
incompatible with our use of __fetch_and_add().  Back-patch to 9.5,
which introduced pg_atomic_fetch_add_u32().

Reviewed by Tom Lane.

Discussion: https://postgr.es/m/20190831071157.GA3251746@rfd.leadboat.com

Back-patch to 9.5, which introduced these functions.

Reviewed by Tom Lane.

Discussion: https://postgr.es/m/20190831071157.GA3251746@rfd.leadboat.com

Add the comments that I griped were missing.  Also re-order tests
so that parallelism-related tests aren't randomly separated from
each other.

Discussion: https://postgr.es/m/CAAaqYe9GD__4Crm=ddz+-XXcNhfY_V5gFYdLdmkFNq=2VHO56Q@mail.gmail.com

Most WAL records are ignored in early SnapBuild snapshot build phases.
But it's critical to process some of them, so that later messages have
the correct transaction state after the snapshot is completely built; in
particular, XLOG_XACT_ASSIGNMENT messages are critical in order for
sub-transactions to be correctly assigned to their parent transactions,
or at least one assert misbehaves, as reported by Ildar Musin.

Diagnosed-by: Masahiko Sawada
Author: Masahiko Sawada
Discussion: https://postgr.es/m/CAONYFtOv+Er1p3WAuwUsy1zsCFrSYvpHLhapC_fMD-zNaRWxYg@mail.gmail.com

Lack of parens in the definitions could cause a statement using these
macros to have unexpected semantics.  In current code no bug is
apparent, but best to fix the definitions to avoid problems down the
line.

Reported-by: Tom Lane
Discussion: https://postgr.es/m/19795.1568400476@sss.pgh.pa.us

The progress state was being clobbered once the first index completed
being rebuilt, causing the final phases of the operation not show
anything in the progress view.  This was inadvertently broken in
03f9e5cb, which added progress tracking for REINDEX.

(The reason this bugfix is this small is that I had already noticed this
problem when writing monitoring for CREATE INDEX, and had already worked
around it, as can be seen in discussion starting at
https://postgr.es/m/20190329150218.GA25010@alvherre.pgsql Fixing the
problem is just a matter of fixing one place touched by the REINDEX
monitoring.)

Reported by: Álvaro Herrera
Author: Álvaro Herrera
Discussion: https://postgr.es/m/20190801184333.GA21369@alvherre.pgsql

Discussion: https://postgr.es/m/CAEkD-mDUZrRE%3Dk-FznEg4Ed2VdjpZCyHoyo%2Bp0%2B8KvHqR%3DpNVQ%40mail.gmail.com
Author: Liudmila Mantrova, Alexander Lakhin
Reviewed-by: Alexander Korotkov, Alvaro Herrera
Backpatch-through: 12

Besides cosmetic improvements it removes statement that operators necessary
need to be separated from operands with spaces, which is not really true.

Discussion: https://postgr.es/m/CAEkD-mDUZrRE%3Dk-FznEg4Ed2VdjpZCyHoyo%2Bp0%2B8KvHqR%3DpNVQ%40mail.gmail.com
Author: Liudmila Mantrova, Alexander Lakhin
Reviewed-by: Alexander Korotkov, Alvaro Herrera
Backpatch-through: 12

Author: Shenhao Wang
Discussion: https://postgr.es/m/63580B24E208E3429D94153A03C68E0901AA8002D5@G08CNEXMBPEKD02.g08.fujitsu.local

Include newitemoff in rmgr desc output for nbtree page split records.
In passing, correct an obsolete comment that claimed that newitemoff is
only logged for _L variant nbtree page split WAL records.

Both issues were oversights in commit 2c03216d, which revamped the
WAL format.

Author: Peter Geoghegan
Backpatch: 9.5-, where the WAL format was revamped.