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
d9fadbf, 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 cfc5008a5, 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 d5406dea25 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 fd6ec93bf8 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 48995040d5 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
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
The refactoring done in a4fd3aa 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 a4fd3aa, 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 5935917ce
back into the originally intended form (cf. 776a2c887, 22864f6e0).
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
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 36da3cfb45 as a global
because its method of operation was devilishly intrincate. Commit
c945af80cf 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 a7ee7c8513 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 f14413b684 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
This has been introduced by c16dc1a 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 4be058fe9 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 22251686f0. 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 9155580fd5. 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 776a2c887, 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 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 258ee1b63, 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 6ef77cf46 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.
The buildfarm says this produces some unexpected output with
force_parallel_mode = regress. There's probably a bug underneath
that, but for the moment just delete the test case to make the
buildfarm green again.
(I now notice that the case had also failed to get updated to follow
commit d52eaa094, which made plan_cache_mode = force_generic_plan
prevail throughout partition_prune.sql; it was thereby managing to
break a later test. When/if we put this back in, *don't* include the
SET and RESET commands.)
Previously, if the startup pruning logic proved that all child nodes
of an Append or MergeAppend could be pruned, we still kept one, just
to keep EXPLAIN from failing. The previous commit removed the
ruleutils.c limitation that required this kluge, so drop it. That
results in less-confusing EXPLAIN output, as per a complaint from
Yuzuko Hosoya.
David Rowley
Discussion: https://postgr.es/m/001001d4f44b$2a2cca50$7e865ef0$@lab.ntt.co.jp
This patch causes EXPLAIN to always assign a separate table alias to the
parent RTE of an append relation (inheritance set); before, such RTEs
were ignored if not actually scanned by the plan. Since the child RTEs
now always have that same alias to start with (cf. commit 55a1954da),
the net effect is that the parent RTE usually gets the alias used or
implied by the query text, and the children all get that alias with "_N"
appended. (The exception to "usually" is if there are duplicate aliases
in different subtrees of the original query; then some of those original
RTEs will also have "_N" appended.)
This results in more uniform output for partitioned-table plans than
we had before: the partitioned table itself gets the original alias,
and all child tables have aliases with "_N", rather than the previous
behavior where one of the children would get an alias without "_N".
The reason for giving the parent RTE an alias, even if it isn't scanned
by the plan, is that we now use the parent's alias to qualify Vars that
refer to an appendrel output column and appear above the Append or
MergeAppend that computes the appendrel. But below the append, Vars
refer to some one of the child relations, and are displayed that way.
This seems clearer than the old behavior where a Var that could carry
values from any child relation was displayed as if it referred to only
one of them.
While at it, change ruleutils.c so that the code paths used by EXPLAIN
deal in Plan trees not PlanState trees. This effectively reverts a
decision made in commit 1cc29fe7c, which seemed like a good idea at
the time to make ruleutils.c consistent with explain.c. However,
it's problematic because we'd really like to allow executor startup
pruning to remove all the children of an append node when possible,
leaving no child PlanState to resolve Vars against. (That's not done
here, but will be in the next patch.) This requires different handling
of subplans and initplans than before, but is otherwise a pretty
straightforward change.
Discussion: https://postgr.es/m/001001d4f44b$2a2cca50$7e865ef0$@lab.ntt.co.jp
This makes such log entries more useful, since the cause of the error
can be dependent on the parameter values.
Author: Alexey Bashtanov, Álvaro Herrera
Discussion: https://postgr.es/m/0146a67b-a22a-0519-9082-bc29756b93a2@imap.cc
Reviewed-by: Peter Eisentraut, Andres Freund, Tom Lane
Since its inception, our Windows signal emulation code has worked by
running a main signal thread that just watches for incoming signal
requests, and then spawns a new thread to handle each such request.
That design is meant for servers in which requests can take substantial
effort to process, and it's worth parallelizing the handling of
requests. But those assumptions are just bogus for our signal code.
It's not much more than pg_queue_signal(), which is cheap and can't
parallelize at all, plus we don't really expect lots of signals to
arrive at the same backend at once. More importantly, this approach
creates failure modes that we could do without: either inability to
spawn a new thread or inability to create a new pipe handle will risk
loss of signals. Hence, dispense with the separate per-signal threads
and just service each request in-line in the main signal thread. This
should be a bit faster (for the normal case of one signal at a time)
as well as more robust.
Patch by me; thanks to Andrew Dunstan for testing and Amit Kapila
for review.
Discussion: https://postgr.es/m/4412.1575748586@sss.pgh.pa.us
It was once possible to do ALTER TABLE ... SET STATISTICS on system
tables without allow_sytem_table_mods. This was changed apparently by
accident between PostgreSQL 9.1 and 9.2, but a code comment still
claimed this was possible. Without that functionality, having a
separate ATPrepSetStatistics() is useless, so use the generic
ATSimplePermissions() instead and move the remaining custom code into
ATExecSetStatistics().
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/cc8d2648-a0ec-7a86-13e5-db473484e19e%402ndquadrant.com
gcc-7 used with a sufficient optimization level complains about warnings
around do_to_timestamp() regarding the initialization and handling of
some of its variables. Recent commits 66c74f8 and d589f94 made things
made the interface more confusing, so document which variables are
always expected and initialize properly the optional ones when they are
set.
Author: Andrey Lepikhov, Michael Paquier
Discussion: https://postgr.es/m/a7e28b83-27b1-4e1c-c76b-4268c4b785bc@postgrespro.ru
Clean up some comments (some generated by old versions of autoconf)
and some random ordering differences, so it's easier to diff this
against the default pg_config.h or pg_config.h.in. Remove LOCALEDIR
handling from pg_config.h.win32 altogether because it's already in
pg_config_paths.h.
This provides a mechanism to emit literal values in informative
messages, such as query parameters. The new code is more complex than
what it replaces, primarily because it wants to be more efficient.
It also has the (currently unused) additional optional capability of
specifying a maximum size to print.
The new function lives out of common/stringinfo.c so that frontend users
of that file need not pull in unnecessary multibyte-encoding support
code.
Author: Álvaro Herrera and Alexey Bashtanov, after a suggestion from Andres Freund
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/20190920203905.xkv5udsd5dxfs6tr@alap3.anarazel.de
On Windows, we use CMD.EXE to redirect the postmaster's stdout/stderr
into a log file. CMD.EXE will open that file with non-sharing-friendly
parameters, and the file will remain open for a short time after the
postmaster has removed postmaster.pid. This can result in an
ERROR_SHARING_VIOLATION failure if we attempt to start a new postmaster
immediately with the same log file (e.g. during "pg_ctl restart").
This seems to explain intermittent buildfarm failures we've been seeing
on Windows machines.
To fix, just open and close the log file using our own pgwin32_open(),
which will wait if necessary to avoid the failure. (Perhaps someday
we should stop using CMD.EXE, but that would be a far more complex
patch, and it doesn't seem worth the trouble ... yet.)
Back-patch to v12. This only solves the problem when frontend fopen()
is redirected to pgwin32_fopen(), which has only been true since commit
0ba06e0bf. Hence, no point in back-patching further, unless we care
to back-patch that change too.
Diagnosis and patch by Alexander Lakhin (bug #16154).
Discussion: https://postgr.es/m/16154-1ccf0b537b24d5e0@postgresql.org
AfterTriggerExecute() retrieves a fresh tuple or pair of tuples from a
tuplestore and then stores the tuple(s) in the passed-in slot(s) if
AFTER_TRIGGER_FDW_FETCH, while it uses the most-recently-retrieved
tuple(s) stored in the slot(s) if AFTER_TRIGGER_FDW_REUSE. This was
done correctly before 12, but commit ff11e7f4b broke it by mistakenly
clearing the tuple(s) stored in the slot(s) in that function, leading to
an assertion failure as reported in bug #16139 from Alexander Lakhin.
Also, fix some other issues with the aforementioned commit in passing:
* For tg_newslot, which is a slot added to the TriggerData struct by the
commit to store new updated tuples, it didn't ensure the slot was NULL
if there was no such tuple.
* The commit failed to update the documentation about the trigger
interface.
Author: Etsuro Fujita
Backpatch-through: 12
Discussion: https://postgr.es/m/16139-94f9ccf0db6119ec%40postgresql.org
pg_signal_dispatch_thread() responded to the client (signal sender)
and disconnected the pipe before actually setting the shared variables
that make the signal visible to the backend process's main thread.
In the worst case, it seems, effective delivery of the signal could be
postponed for as long as the machine has any other work to do.
To fix, just move the pg_queue_signal() call so that we do it before
responding to the client. This essentially makes pgkill() synchronous,
which is a stronger guarantee than we have on Unix. That may be
overkill, but on the other hand we have not seen comparable timing bugs
on any Unix platform.
While at it, add some comments to this sadly underdocumented code.
Problem diagnosis and fix by Amit Kapila; I just added the comments.
Back-patch to all supported versions, as it appears that this can cause
visible NOTIFY timing oddities on all of them, and there might be
other misbehavior due to slow delivery of other signals.
Discussion: https://postgr.es/m/32745.1575303812@sss.pgh.pa.us
isolationtester.c had a hard-wired limit of 3 minutes per test step.
It now emerges that this isn't quite enough for some of the slowest
buildfarm animals. This isn't the first time we've had to raise
this limit (cf. 1db439ad4), so let's make it configurable. This
patch raises the default to 5 minutes, and introduces an environment
variable PGISOLATIONTIMEOUT that can be set if more time is needed,
following the precedent of PGCTLTIMEOUT.
Also, modify isolationtester so that when the timeout is hit,
it explicitly reports having sent a cancel. This makes the regression
failure log considerably more intelligible. (In the worst case, a
timed-out test might actually be reported as "passing" without this
extra output, so arguably this is a bug fix in itself.)
In passing, update the README file, which had apparently not gotten
touched when we added "make check" support here.
Back-patch to 9.6; older versions don't have comparable timeout logic.
Discussion: https://postgr.es/m/22964.1575842935@sss.pgh.pa.us
