Tuple conversion support in tupconvert.c is able to convert rowtypes
between two relations, inner and outer, which are logically equivalent
but have a different ordering or even dropped columns (used mainly for
inheritance tree and partitions).  This makes use of attribute mappings,
which are simple arrays made of AttrNumber elements with a length
matching the number of attributes of the outer relation.  The length of
the attribute mapping has been treated as completely independent of the
mapping itself until now, making it easy to pass down an incorrect
mapping length.

This commit refactors the code related to attribute mappings and moves
it into an independent facility called attmap.c, extracted from
tupconvert.c.  This merges the attribute mapping with its length,
avoiding to try to guess what is the length of a mapping to use as this
is computed once, when the map is built.

This will avoid mistakes like what has been fixed in dc816e58, which has
used an incorrect mapping length by matching it with the number of
attributes of an inner relation (a child partition) instead of an outer
relation (a partitioned table).

Author: Michael Paquier
Reviewed-by: Amit Langote
Discussion: https://postgr.es/m/20191121042556.GD153437@paquier.xyz

This patch allows building the local relmap cache for a subscribed
relation after processing pending invalidation messages and potential
relcache updates.  Without this, the attributes in the local cache don't
tally with the updated relcache entry leading to invalid memory access.

Reported-by Jehan-Guillaume de Rorthais
Author: Jehan-Guillaume de Rorthais and Vignesh C
Reviewed-by: Amit Kapila
Backpatch-through: 10
Discussion: https://postgr.es/m/20191025175929.7e90dbf5@firost

That's more consistent with the style we have been using with for
example EXPLAIN, VACUUM or ANALYZE (this one had only one option in
v11).  Based on a suggestion from Pavel Stehule.

Author: Josef Šimánek
Discussion: https://postgr.es/m/CAFj8pRCrUS+eMFvssVPGZN-VDEMP3XN+1Dop0=CmeBq2D+dqOg@mail.gmail.com
Discussion: https://postgr.es/m/CAFp7QwpeMPEtAR5AYpsG623ooMWX03wMjq5cpZn=X+6OCkfwJw@mail.gmail.com

These have been missed in 01368e5d, and count for plpython and the
backend's tsearch code.

Author: Mahendra Singh
Discussion: https://postgr.es/m/CAKYtNAo4mxRRyDB0YqE6QLh17XD7pPQotpGm3GnHS+gQKz4zQQ@mail.gmail.com

Reported-by: Ranier Vilela

Discussion: https://postgr.es/m/MN2PR18MB2927E73FADCA8967B2302469E3490@MN2PR18MB2927.namprd18.prod.outlook.com

Author: Ranier Vilela

Backpatch-through: master

This changes the routines in charge of recycling WAL segments past the
last redo LSN to not use anymore "RedoRecPtr" as a local variable, which
is also available in the context of the session as a static declaration,
replacing it with "lastredoptr".  This confusion has been introduced by
d9fadbf1, so backpatch down to v11 like the other commit.

Thanks to Tom Lane, Robert Haas, Alvaro Herrera, Mark Dilger and Kyotaro
Horiguchi for the input provided.

Author: Ranier Vilela
Discussion: https://postgr.es/m/MN2PR18MB2927F7B5F690065E1194B258E35D0@MN2PR18MB2927.namprd18.prod.outlook.com
Backpatch-through: 11

If CheckAttributeType() threw an error about the datatype of an
index expression column, it would report an empty column name,
which is pretty unhelpful and certainly not the intended behavior.
I (tgl) evidently broke this in commit cfc5008a, by not noticing
that the column's attname was used above where I'd placed the
assignment of it.

In HEAD and v12, this is trivially fixable by moving up the
assignment of attname.  Before v12 the code is a bit more messy;
to avoid doing substantial refactoring, I took the lazy way out
and just put in two copies of the assignment code.

Report and patch by Amit Langote.  Back-patch to all supported
branches.

Discussion: https://postgr.es/m/CA+HiwqFA+BGyBFimjiYXXMa2Hc3fcL0+OJOyzUNjhU4NCa_XXw@mail.gmail.com

Commit d5406dea used a slightly
novel, and wrong, approach to compute the length of the last
toast chunk. It worked fine unless the last chunk happened to
have the largest possible size.

Rework some of the checks for bad TOAST chunks to be a bit simpler
and easier to understand. These checks verify that (1) we get all
and only the chunk numbers we expect to see and (2) each chunk has
the expected size. However, the existing code was a bit hard to
understand, at least for me; try to make it clearer.

As part of that, have toast_fetch_datum_slice check the relationship
between endchunk and totalchunks only with an Assert() rather than
checking every chunk number against both values. There's no need to
check that relationship in production builds because it's not a
function of whether on-disk corruption is present; it's just a
question of whether the code does the right math.

Also, have toast_fetch_datum_slice() use ereport(ERROR) rather than
elog(ERROR). Commit fd6ec93b made
the two functions inconsistent with each other.

Rename assorted variables for better clarity and consistency, and
move assorted variables from function scope to the function's main
loop. Remove a few variables that are used only once entirely.

Patch by me, reviewed by Peter Eisentraut.

Discussion: http://postgr.es/m/CA+TgmobBzxwFojJ0zV0Own3dr09y43hp+OzU2VW+nos4PMXWEg@mail.gmail.com

Commit 48995040 removed the largest
barrier to use of simplehash in frontend code, but there's one more
problem: it uses elog(ERROR, ...) or elog(LOG, ...) in a couple of
places. Work around that by changing those to pg_log_error() and
pg_log_info() when FRONTEND is defined.

Patch by me, reviewed by Andres Freund.

Discussion: http://postgr.es/m/CA+Tgmob8oyh02NrZW=xCScB+5GyJ-jVowE3+TWTUmPF=FsGWTA@mail.gmail.com

If the SH_RAW_ALLOCATOR is defined, it will be used to allocate bytes
for the hash table, and no dependencies on MemoryContext will exist.
This means, in particular, that the SH_CREATE function will not take
a MemoryContext argument.

Patch by me, reviewed by Andres Freund.

Discussion: http://postgr.es/m/CA+Tgmob8oyh02NrZW=xCScB+5GyJ-jVowE3+TWTUmPF=FsGWTA@mail.gmail.com

Commit 5910d6c7 got this wrong.

Report and patch by Andrew Gierth.

Discussion: http://postgr.es/m/8736diaj98.fsf@news-spur.riddles.org.uk

Where possible, share signal handler code and main loop interrupt
checking. This saves quite a bit of code and should simplify
maintenance, too.

This commit intends not to change the way anything works, even
though that might allow more code to be unified. It does unify
a bunch of individual variables into a ShutdownRequestPending
flag that has is now used by a bunch of different process types,
though.

Patch by me, reviewed by Andres Freund and Daniel Gustafsson.

Discussion: http://postgr.es/m/CA+TgmoZwDk=BguVDVa+qdA6SBKef=PKbaKDQALTC_9qoz1mJqg@mail.gmail.com

There seems to be no reason for every background process to have
its own flag indicating that a config-file reload is needed.
Instead, let's just use ConfigFilePending for that purpose
everywhere.

Patch by me, reviewed by Andres Freund and Daniel Gustafsson.

Discussion: http://postgr.es/m/CA+TgmoZwDk=BguVDVa+qdA6SBKef=PKbaKDQALTC_9qoz1mJqg@mail.gmail.com

Some auxiliary processes, as well as the autovacuum launcher,
have interrupt handling code directly in their main loops.
Try to abstract things a little better by moving it into
separate functions.

This doesn't make any functional difference, and leaves
in place relatively large differences among processes in how
interrupts are handled, but hopefully it at least makes it
easier to see the commonalities and differences across
process types.

Patch by me, reviewed by Andres Freund and Daniel Gustafsson.

Discussion: http://postgr.es/m/CA+TgmoZwDk=BguVDVa+qdA6SBKef=PKbaKDQALTC_9qoz1mJqg@mail.gmail.com

This Assert thought that an overflowed transaction can never get registered
for the group update.  But that is not true, because even when the number
of children for a transaction got reduced, the overflow flag is not
changed.  And, for group update, we only care about the current number of
children for a transaction that is being committed.

Based on comments by Andres Freund, remove a redundant Assert in
TransactionIdSetPageStatus as we already had a static Assert for the same
condition a few lines earlier.

Reported-by: Vignesh C
Author: Dilip Kumar
Reviewed-by: Amit Kapila
Backpatch-through: 11
Discussion: https://postgr.es/m/CAFiTN-s5=uJw-Z6JC9gcqtBSjXsrHnU63PXBrA=pnBjqnkm5UA@mail.gmail.com

Rename two function-style macros, removing the word "inner".  This makes
things more consistent.

The refactoring done in a4fd3aa7 for query cancellation has messed up
with the logic in psql by mixing CancelRequested and cancel_pressed,
breaking for example \watch.  The former would be switched to true if a
cancellation request has been attempted and that it actually succeeded,
and the latter tracks if a cancellation attempt has been done.

This commit brings back the code of psql to a state consistent to what
it was before a4fd3aa7, without giving up on the refactoring pieces
introduced.  It should be actually possible to merge more both flags as
their concepts are close enough, however note that psql's --single-step
mode relies on cancel_pressed to be always set, so this requires more
careful analysis left for later.

While on it, fix the declarations of CancelRequested (in cancel.c) and
cancel_pressed (in psql) to be volatile sig_atomic_t.  Previously,
both were declared as booleans, which should be fine on modern
platforms, but the C standard recommends the use of sig_atomic_t for
variables used in signal handlers.  Note that since its introduction in
a1792320, CancelRequested declaration was not volatile.

Reported-by: Jeff Janes
Author: Michael Paquier
Discussion: https://postgr.es/m/CAMkU=1zpoUDGKqWKuMWkj7t-bOCaJDx0r=5te_-d0B2HVLABXg@mail.gmail.com

force_parallel_mode = regress is supposed to force use of a Gather
node without having any impact on EXPLAIN output.  But it failed to
accomplish that if both ANALYZE and VERBOSE are given, because that
enables per-worker output data that you wouldn't see if the Gather
hadn't been inserted.  Improve the logic so that we suppress the
per-worker data too.

This allows putting the new test case added by commit 5935917c
back into the originally intended form (cf. 776a2c88, 22864f6e).
We can also get rid of a kluge in subselect.sql, which previously
had to clean up after force_parallel_mode's failure to do what it
said on the tin.

Discussion: https://postgr.es/m/18445.1576177309@sss.pgh.pa.us

get_actual_variable_range() hasn't used a dirty snapshot since commit
3ca930fc, which invented a new snapshot type specifically to meet
selfuncs.c's requirements (HeapTupleSatisfiesNonVacuumable() type
snapshots were added).

Discussion: https://postgr.es/m/CAH2-Wzn2pSqEOcBDAA40CnO82oEy-EOpE2bNh_XL_cfFoA86jw@mail.gmail.com

Attempting to open a file fails with ERROR_ACCESS_DENIED if the file
is flagged for deletion but not yet actually gone (another in a long
list of reasons why Windows is broken, if you ask me).  This seems
likely to explain a lot of irreproducible failures we see in the
buildfarm.  This state generally persists for only a millisecond or so,
so just wait a bit and retry.  If it's a real permissions problem,
we'll eventually give up and report it as such.  If it's the pending
deletion case, we'll see file-not-found and report that after the
deletion completes, and the caller will treat that in an appropriate
way.

In passing, rejigger the existing retry logic for some other error
cases so that we don't uselessly wait an extra time when we're
not going to retry anymore.

Alexander Lakhin (with cosmetic tweaks by me).  Back-patch to all
supported branches, since this seems like a pretty safe change and
the problem is definitely real.

Discussion: https://postgr.es/m/16161-7a985d2f1bbe8f71@postgresql.org

recoveryDelayUntilTime was introduced by commit 36da3cfb as a global
because its method of operation was devilishly intrincate.  Commit
c945af80 removed all that complexity and could have turned it into a
local variable, but didn't.  Do so now.

Discussion: https://postgr.es/m/20191213200751.GA10731@alvherre.pgsql
Reviewed-by: Michaël Paquier, Daniel Gustafsson

Commit a7ee7c85 fixed a bug in GiST page split during index creation,
where we failed to re-find the position of a downlink after the page
containing it was split. However, that fix was incomplete; the other call
to gistinserttuples() in the same function needs to also clear
'downlinkoffnum'.

Fixes bug #16134 reported by Alexander Lakhin, for real this time. The
previous fix was enough to fix the crash with the reproducer script for
bug #16162, but the original script for #16134 was still crashing.

Backpatch to v12, like the previous incomplete fix.

Discussion: https://www.postgresql.org/message-id/d869f537-abe4-d2ea-0510-38cd053f5152%40gmail.com

Commit f14413b6 broke the build of
Perl-using modules on Windows.

Perl might have its own definitions of uid_t and gid_t, so we hide
ours, but then we can't use ours in our header files such as port.h
which don't see the Perl definition.

Hide our definition of getpeereid() on Windows in Perl-using modules,
using PLPERL_HAVE_UID_GID define.  That means we can't portably use
getpeeruid() is such modules right now, but there is no need anyway.

The getpeereid() uses have so far been protected by HAVE_UNIX_SOCKETS,
so they didn't ever care about Windows support.  But in anticipation
of Unix-domain socket support on Windows, that needs to be handled
differently.

Windows doesn't support getpeereid() at this time, so we use the
existing not-supported code path.  We let configure do its usual thing
of picking up the replacement from libpgport, instead of the custom
overrides that it was doing before.

But then Windows doesn't have struct passwd, so this patch sprinkles
some additional #ifdef WIN32 around to make it work.  This is similar
to existing code that deals with this issue.
Reviewed-by: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/5974caea-1267-7708-40f2-6009a9d653b0@2ndquadrant.com

Also, add a comment explaining a test case.

Back-patch to 11 where the regression test was added.

Discussion: https://postgr.es/m/CAPmGK15adZPh2B%2BmGUjSOMH%2BH39ogDRWfCfm4G6jncZCAs9V_Q%40mail.gmail.com

This has been introduced by c16dc1ac since progress reporting for VACUUM
has been added.  As this issue just causes some extra work and is
harmless, no backpatch is done.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20191213030831.GT2082@telsasoft.com

It appears that a concurrent autovacuum/autoanalyze run can cause
changes in the plans expected by this test.  To prevent that, change
the tables it uses to be temp tables --- there's no need for them
to be permanent, and this should save a few cycles too.

Discussion: https://postgr.es/m/3244.1576160824@sss.pgh.pa.us

The RTE_RESULT simplification logic added by commit 4be058fe had a
flaw: it would collapse out a RTE_RESULT that is due to compute a
PlaceHolderVar, and reassign the PHV to the parent join level, even if
another input relation of the join contained a lateral reference to
the PHV.  That can't work because the PHV would be computed too late.
In practice it led to failures of internal sanity checks later in
planning (either assertion failures or errors such as "failed to
construct the join relation").

To fix, add code to check for the presence of such PHVs in relevant
portions of the query tree.  Notably, this required refactoring
range_table_walker so that a caller could ask to walk individual RTEs
not the whole list.  (It might be a good idea to refactor
range_table_mutator in the same way, if only to keep those functions
looking similar; but I didn't do so here as it wasn't necessary for
the bug fix.)

This exercise also taught me that find_dependent_phvs(), as it stood,
could only safely be used on the entire Query, not on subtrees.
Adjust its API to reflect that; which in passing allows it to have
a fast path for the common case of no PHVs anywhere.

Per report from Will Leinweber.  Back-patch to v12 where the bug
was introduced.

Discussion: https://postgr.es/m/CALLb-4xJMd4GZt2YCecMC95H-PafuWNKcmps4HLRx2NHNBfB4g@mail.gmail.com

When loading DH parameters used for the generation of ephemeral DH keys
in the backend, the code has never bothered releasing the memory used
for the DH information loaded from a file or from libpq's default.  This
commit makes sure that the information is properly free()'d.

Note that as SSL parameters can be reloaded, this can cause an accumulation
of memory leaked.  As the leak is minor, no backpatch is done.

Reported-by: Dmitry Uspenskiy
Discussion: https://postgr.es/m/16160-18367e56e9a28264@postgresql.org

The previous commit failed to consider that FileGetRawDesc() might
not return a valid fd, as discovered on the build farm.  Switch to
using the File interface only.

Back-patch to 12, like the previous commit.

_mdfd_getseg() opens all segments up to the requested one.  That
causes problems for mdsyncfiletag(), if mdunlinkfork() has
already unlinked other segment files.  Open the file we want
directly by name instead, if it's not already open.

The consequence of this bug was a rare panic in the checkpointer,
made more likely if you saturated the sync request queue so that
the SYNC_FORGET_REQUEST messages for a given relation were more
likely to be absorbed in separate cycles by the checkpointer.

Back-patch to 12.  Defect in commit 3eb77eba.

Author: Thomas Munro
Reported-by: Justin Pryzby
Discussion: https://postgr.es/m/20191119115759.GI30362%40telsasoft.com

The bug was similar to the one that was fixed in commit 22251686. When
we split page X and insert the downlink for the new page, the parent page
might also need to be split. When that happens, the downlink offset number
we remembered for X is no longer valid. We correctly called
gistFindCorrectParent() to re-find it, but gistFindCorrectParent() doesn't
do anything if the LSN of the page hasn't changed, and we stopped updating
LSNs during index build in commit 9155580f. The buggy codepath was taken
if the page was split into three or more pages, and inserting the downlink
caused the parent page to split. To fix, explicitly mark the downlink
offset number as invalid, to force gistFindCorrectParent() to re-find it.

Fixes bug #16134 reported by Alexander Lakhin, reported again as #16162 by
Andreas Kunert. Thanks to Jeff Janes, Tom Lane and Tomas Vondra for
debugging. Backpatch to v12, where we stopped WAL-logging during index
build.

Discussion: https://www.postgresql.org/message-id/16134-0423f729671dec64%40postgresql.org
Discussion: https://www.postgresql.org/message-id/16162-45d21b7b6c1a3105%40postgresql.org

Prefer to call "rl_filename_completion_function" and
"rl_completion_matches", rather than using the names without the rl_
prefix.  This matches Readline's documentation, and makes our code
a little clearer about which names are external.  On platforms that
only have the un-prefixed names (just some very ancient versions of
libedit, AFAICT), reverse the direction of the compatibility macro
definitions to match.

Also, remove our extern declaration of "filename_completion_function";
whatever libedit versions may have failed to declare that are surely
dead and buried.

Discussion: https://postgr.es/m/23608.1576248145@sss.pgh.pa.us

This undoes my hurried commit 776a2c88, restoring the removed test case
in a form that passes with or without force_parallel_mode = regress.

It turns out that force_parallel_mode = regress simply fails to mask
the Worker lines that will be produced by EXPLAIN (ANALYZE, VERBOSE).
I'd say that's a bug in that feature, as its entire alleged reason
for existence is to make the EXPLAIN output the same.  It's certainly
not a bug in the plan node pruning logic.  Fortunately, this test case
doesn't really need to use ANALYZE, so just drop that.

Discussion: https://postgr.es/m/18891.1576109690@sss.pgh.pa.us

The test cases added by commit 26ae3aa8 exposed an old oversight in
timestamp[tz]_part: they didn't correct the result of date2isoyear()
for BC years, so that we produced an off-by-one answer for such years.
Fix that, and back-patch to all supported branches.

Discussion: https://postgr.es/m/SG2PR06MB37762CAE45DB0F6CA7001EA9B6550@SG2PR06MB3776.apcprd06.prod.outlook.com

The DTK_DOW/DTK_ISODOW and DTK_DOY switch cases in timestamp_part() and
timestamptz_part() contained calls of timestamp2tm() that were fully
redundant with the ones done just above the switch.  This evidently crept
in during commit 258ee1b6, which relocated that code from another place
where the calls were indeed needed.  Just delete the redundant calls.

I (tgl) noted that our test coverage of these functions left quite a
bit to be desired, so extend timestamp.sql and timestamptz.sql to
cover all the branches.

Back-patch to all supported branches, as the previous commit was.
There's no real issue here other than some wasted cycles in some
not-too-heavily-used code paths, but the test coverage seems valuable.

Report and patch by Li Japin; test case adjustments by me.

Discussion: https://postgr.es/m/SG2PR06MB37762CAE45DB0F6CA7001EA9B6550@SG2PR06MB3776.apcprd06.prod.outlook.com

gcc-based Windows buildfarm animals are not happy about a multiline
regular expression I added recently.  Try to accomodate; existing
pg_basebackup tests suggest that \n should work instead of a bare
newline, but throw in \r also.  This being perl, TIMTOWTDI.
Also remove the pointless $ at the end of the pattern, for extra luck.

(If this doesn't work, I'll probably just split the regex in two.)

Per buildfarm members jacana and fairywren.

Discussion: https://postgr.es/m/3562.1576161217@sss.pgh.pa.us

This is made necessary by the fact that commit 6ef77cf4 added
AppendRelInfos to plan trees.  I'd concluded that this extra code was
not necessary because we don't transmit that data to parallel workers
... but I forgot about -DWRITE_READ_PARSE_PLAN_TREES.  Per buildfarm.