| Commit message (Collapse) | Author | Age |
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It is equivalent in ANSI C to write (*funcptr) () and funcptr(). These
two styles have been applied inconsistently. After discussion, we'll
use the more verbose style for plain function pointer variables, to make
it clear that it's a variable, and the shorter style when the function
pointer is in a struct (s.func() or s->func()), because then it's clear
that it's not a plain function name, and otherwise the excessive
punctuation makes some of those invocations hard to read.
Discussion: https://www.postgresql.org/message-id/f52c16db-14ed-757d-4b48-7ef360b1631d@2ndquadrant.com
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This doesn't allow routing tuple to the foreign partitions themselves,
but it permits tuples to be routed to regular partitions despite the
presence of foreign partitions in the same inheritance hierarchy.
Etsuro Fujita, reviewed by Amit Langote and by me.
Discussion: http://postgr.es/m/bc3db4c1-1693-3b8a-559f-33ad2b50b7ad@lab.ntt.co.jp
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Issuing a savepoint-related command in a Query message that contains
multiple SQL statements led to a FATAL exit with a complaint about
"unexpected state STARTED". This is a shortcoming of commit 4f896dac1,
which attempted to prevent such misbehaviors in multi-statement strings;
its quick hack of marking the individual statements as "not top-level"
does the wrong thing in this case, and isn't a very accurate description
of the situation anyway.
To fix, let's introduce into xact.c an explicit model of what happens for
multi-statement Query strings. This is an "implicit transaction block
in progress" state, which for many purposes works like the normal
TBLOCK_INPROGRESS state --- in particular, IsTransactionBlock returns true,
causing the desired result that PreventTransactionChain will throw error.
But in case of error abort it works like TBLOCK_STARTED, allowing the
transaction to be cancelled without need for an explicit ROLLBACK command.
Commit 4f896dac1 is reverted in toto, so that we go back to treating the
individual statements as "top level". We could have left it as-is, but
this allows sharpening the error message for PreventTransactionChain
calls inside functions.
Except for getting a normal error instead of a FATAL exit for savepoint
commands, this patch should result in no user-visible behavioral change
(other than that one error message rewording). There are some things
we might want to do in the line of changing the appearance or wording of
error and warning messages around this behavior, which would be much
simpler to do now that it's an explicitly modeled state. But I haven't
done them here.
Although this fixes a long-standing bug, no backpatch. The consequences
of the bug don't seem severe enough to justify the risk that this commit
itself creates some new issue.
Patch by me, but it owes something to previous investigation by
Takayuki Tsunakawa, who also reported the bug in the first place.
Also thanks to Michael Paquier for reviewing.
Discussion: https://postgr.es/m/0A3221C70F24FB45833433255569204D1F6BE40D@G01JPEXMBYT05
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In the generic atomic ops that rely on a loop around a CAS primitive,
there's no need to force the initial read of the "old" value to be atomic.
In the typically-rare case that we get a torn value, that simply means
that the first CAS attempt will fail; but it will update "old" to the
atomically-read value, so the next attempt has a chance of succeeding.
It was already being done that way in pg_atomic_exchange_u64_impl(),
but let's duplicate the approach in the rest.
(Given the current coding of the pg_atomic_read functions, this change
is a no-op anyway on popular platforms; it only makes a difference where
pg_atomic_read_u64_impl() is implemented as a CAS.)
In passing, also remove unnecessary take-a-pointer-and-dereference-it
coding in the pg_atomic_read functions. That seems to have been based
on a misunderstanding of what the C standard requires. What actually
matters is that the pointer be declared as pointing to volatile, which
it is.
I don't believe this will change the assembly code at all on x86
platforms (even ignoring the likelihood that these implementations
get overridden by others); but it may help on less-mainstream CPUs.
Discussion: https://postgr.es/m/13707.1504718238@sss.pgh.pa.us
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recovery_target_time accepts timestamp input, though
does not allow use of special values, e.g. “today”.
Report a useful error message for these cases.
Reported-by: Piotr Stefaniak
Author: Simon Riggs
Discussion: https://postgr.es/m/CANP8+jJdKA+BkkYLWz9zAm16Y0s2ExBv0WfpAwXdTpPfWnA9Bg@mail.gmail.com
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Saves ~150 lines, costs little.
Fabien Coelho, reviewed by Victor Drobny
Discussion: https://postgr.es/m/alpine.DEB.2.20.1703311958001.14355@lancre
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Index columns are referenced by ordinal number rather than name, e.g.
CREATE INDEX coord_idx ON measured (x, y, (z + t));
ALTER INDEX coord_idx ALTER COLUMN 3 SET STATISTICS 1000;
Incompatibility note for release notes:
\d+ for indexes now also displays Stats Target
Authors: Alexander Korotkov, with contribution by Adrien NAYRAT
Review: Adrien NAYRAT, Simon Riggs
Wordsmith: Simon Riggs
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In addition to __sync_fetch_and_add, gcc offers __sync_fetch_and_sub,
__sync_fetch_and_and, and __sync_fetch_and_or, which correspond directly
to primitive atomic ops that we want. Testing shows that in some cases
they generate better code than our generic implementations, so use them.
We've assumed that configure's test for __sync_val_compare_and_swap is
sufficient to allow assuming that __sync_fetch_and_add is available, so
make the same assumption for these functions. Should that prove to be
wrong, we can add more configure tests.
Yura Sokolov, reviewed by Jesper Pedersen and myself
Discussion: https://postgr.es/m/7f65886daca545067f82bf2b463b218d@postgrespro.ru
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The pg_atomic_compare_exchange_xxx functions are defined to update
*expected to whatever they read from the target variable. Therefore,
there's no need to do additional explicit reads after we've initialized
the "old" variable. The actual benefit of this is somewhat debatable,
but it seems fairly unlikely to hurt anything, especially since we
will override the generic implementations in most performance-sensitive
cases.
Yura Sokolov, reviewed by Jesper Pedersen and myself
Discussion: https://postgr.es/m/7f65886daca545067f82bf2b463b218d@postgrespro.ru
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The NAMEDTUPLESTORE patch piggybacked on the infrastructure for
TABLEFUNC/VALUES/CTE RTEs, none of which can ever have dropped columns,
so the possibility was ignored most places. Fix that, including adding a
specification to parsenodes.h about what it's supposed to look like.
In passing, clean up assorted comments that hadn't been maintained
properly by said patch.
Per bug #14799 from Philippe Beaudoin. Back-patch to v10.
Discussion: https://postgr.es/m/20170906120005.25630.84360@wrigleys.postgresql.org
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This command acts somewhat like \g, but instead of executing the query
buffer, it merely prints a description of the columns that the query
result would have. (Of course, this still requires parsing the query;
if parse analysis fails, you get an error anyway.) We accomplish this
using an unnamed prepared statement, which should be invisible to psql
users.
Pavel Stehule, reviewed by Fabien Coelho
Discussion: https://postgr.es/m/CAFj8pRBhYVvO34FU=EKb=nAF5t3b++krKt1FneCmR0kuF5m-QA@mail.gmail.com
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There's no particular reason to target this module for the first
wholesale application of these macros; but we gotta start somewhere.
Ashutosh Bapat and Jeevan Chalke
Discussion: https://postgr.es/m/CAFjFpRcNr3r=u0ni=7A4GD9NnHQVq+dkFafzqo2rS6zy=dt1eg@mail.gmail.com
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It has not been used in a long time, and it doesn't seem safe anyway, so
drop it.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
Reviewed-by: Ryan Murphy <ryanfmurphy@gmail.com>
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The parenthesized style has only been used in a few modules. Change
that to use the style that is predominant across the whole tree.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
Reviewed-by: Ryan Murphy <ryanfmurphy@gmail.com>
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Surely everyone has that by now.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
Reviewed-by: Ryan Murphy <ryanfmurphy@gmail.com>
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This moves the data directories from using temporary directories with
randomness in the directory name to a static name, to make it easier to
debug. The data directory will be retained if tests fail or the test
code dies/exits with failure, and is automatically removed on the next
make check.
If the environment variable PG_TEST_NOCLEAN is defined, the data
directories will be retained regardless of test or exit status.
Author: Daniel Gustafsson <daniel@yesql.se>
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This allows the user's environment to set up a psql-specific choice
of pager, in much the same way that we provide PSQL_EDITOR to allow
a psql-specific override of the more widely known EDITOR variable.
Pavel Stehule, reviewed by Thomas Munro
Discussion: https://postgr.es/m/CAFj8pRD3RRk9S1eRbnGm_T6brc3Ss5mohraNzTSJquzx+pmtKA@mail.gmail.com
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Throttling for sending a base backup in walsender is broken for the case
where there is a lot of WAL traffic, because the latch used to put the
walsender to sleep is also signalled by regular WAL traffic (and each
signal causes an additional batch of data to be sent); the net effect is
that there is no or little actual throttling. This is undesirable, so
rewrite the sleep into a loop to achieve the desired effeect.
Author: Jeff Janes, small tweaks by me
Reviewed-by: Antonin Houska
Discussion: https://postgr.es/m/CAMkU=1xH6mde-yL-Eo1TKBGNd0PB1-TMxvrNvqcAkN-qr2E9mw@mail.gmail.com
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We already had a psql variable VERSION that shows the verbose form of
psql's own version. Add VERSION_NAME to show the short form (e.g.,
"11devel") and VERSION_NUM to show the numeric form (e.g., 110000).
Also add SERVER_VERSION_NAME and SERVER_VERSION_NUM to show the short and
numeric forms of the server's version. (We'd probably add SERVER_VERSION
with the verbose string if it were readily available; but adding another
network round trip to get it seems too expensive.)
The numeric forms, in particular, are expected to be useful for scripting
purposes, now that psql can do conditional tests.
Fabien Coelho, reviewed by Pavel Stehule
Discussion: https://postgr.es/m/alpine.DEB.2.20.1704020917220.4632@lancre
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The previous format with variable names and descriptions in separate
columns was extremely constraining about the length of the descriptions.
We'd dealt with that in several inconsistent ways over the years,
including letting the lines run over 80 characters, breaking descriptions
into multiple lines, or shoving the description onto a separate line.
But it's been a long time since the output could realistically fit onto
a single screen vertically, so let's just rely even more heavily on the
pager to deal with the vertical distance, and split each entry into two
(or more) lines, in the format
variable-name
variable description goes here
Each variable name + description remains a single translatable string,
in hopes of reducing translator confusion; we're just changing the
embedded whitespace.
I failed to resist the temptation to copy-edit one or two of the
descriptions while at it.
Discussion: https://postgr.es/m/2947.1504542679@sss.pgh.pa.us
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process_backslash_command would drop the last character of the input
command on the assumption that it was a newline. Given a non newline
terminated input file, this could result in dropping the last character
of the command. Fix that by doing an actual test that we're removing
a newline.
While at it, allow for Windows newlines (\r\n), and suppress multiple
newlines if any. I do not think either of those cases really occur,
since (a) we read script files in text mode and (b) the lexer stops
when it hits a newline. But it's cheap enough and it provides a
stronger guarantee about what the result string looks like.
This is just cosmetic, I think, since the possibly-overly-chomped
line was only used for display not for further processing. So
it doesn't seem necessary to back-patch.
Fabien Coelho, reviewed by Nikolay Shaplov, whacked around a bit by me
Discussion: https://postgr.es/m/alpine.DEB.2.20.1704171422500.4025@lancre
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With --latency-limit, transactions might get skipped even beyond the
transaction count limit specified by -t, throwing off the expected
number of transactions and thus the denominator for later stats.
Be sure to stop skipping transactions once -t is reached.
Also, include skipped transactions in the "cnt" fields; this requires
discounting them again in a couple of places, but most places are
better off with this definition. In particular this is needed to
get correct overall stats for the combination of -R/-L/-t options.
Merge some more processing into processXactStats() to simplify this.
In passing, add a check that --progress-timestamp is specified only
when --progress is.
We might consider back-patching this, but given that it only matters
for a combination of options, and given the lack of field complaints,
consensus seems to be not to bother.
Fabien Coelho, reviewed by Nikolay Shaplov
Discussion: https://postgr.es/m/alpine.DEB.2.20.1704171422500.4025@lancre
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This puts it in sync with psql's notion of what is a valid variable name.
Like psql, we document that "non-Latin letters" are allowed, but actually
any non-ASCII character is accepted.
Fabien Coelho
Discussion: https://postgr.es/m/20170405.094548.1184280384967203518.t-ishii@sraoss.co.jp
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Discussion: https://postgr.es/m/20170828130545.sdajqlpr37hmmd6a@alvherre.pgsql
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Some compilers complain, not unreasonably, about left-shifting an
int32 "1" and then assigning the result to an int64. In practice
I sure hope that this data structure never gets large enough that
an overflow would actually occur; but let's cast the constant to
the right type to avoid the hazard.
In passing, fix a typo in dshash.h.
Amit Kapila, adjusted as per comment from Thomas Munro.
Discussion: https://postgr.es/m/CAA4eK1+5vfVMYtjK_NX8O3-42yM3o80qdqWnQzGquPrbq6mb+A@mail.gmail.com
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In commit 9d6b160d7, I tweaked pg_config.h.win32 to use
"#define HAVE_LONG_LONG_INT_64 1" rather than defining it as empty,
for consistency with what happens in an autoconf'd build.
But Solution.pm injects another definition of that macro into
ecpg_config.h, leading to justifiable (though harmless) compiler whining.
Make that one consistent too. Back-patch, like the previous patch.
Discussion: https://postgr.es/m/CAEepm=1dWsXROuSbRg8PbKLh0S=8Ou-V8sr05DxmJOF5chBxqQ@mail.gmail.com
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Move the responsibility for creating/destroying TupleQueueReaders into
execParallel.c, to avoid duplicative coding in nodeGather.c and
nodeGatherMerge.c. Also, instead of having DestroyTupleQueueReader do
shm_mq_detach, do it in the caller (which is now only ExecParallelFinish).
This means execParallel.c does both the attaching and detaching of the
tuple-queue-reader shm_mqs, which seems less weird than the previous
arrangement.
These changes also eliminate a vestigial memory leak (of the pei->tqueue
array). It's now demonstrable that rescans of Gather or GatherMerge don't
leak memory.
Discussion: https://postgr.es/m/8670.1504192177@sss.pgh.pa.us
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Add the maxrss field to the getrusage output (log_*_stats). This was
previously omitted because of portability concerns, but we feel this
might not be a concern anymore.
based on patch by Justin Pryzby <pryzby@telsasoft.com>
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This probably doesn't save anything meaningful in terms of
performance, but making the code simpler is a good idea anyway.
Code by Beena Emerson, extracted from a larger patch by Jeevan
Ladhe, slightly adjusted by me.
Discussion: http://postgr.es/m/CAOgcT0ONgwajdtkoq+AuYkdTPY9cLWWLjxt_k4SXue3eieAr+g@mail.gmail.com
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Instead of using a cast to force the constant to be the right width,
assume we can plaster on an L, UL, LL, or ULL suffix as appropriate.
The old approach to this is very hoary, dating from before we were
willing to require compilers to have working int64 types.
This fix makes the PG_INT64_MIN, PG_INT64_MAX, and PG_UINT64_MAX
constants safe to use in preprocessor conditions, where a cast
doesn't work. Other symbolic constants that might be defined using
[U]INT64CONST are likewise safer than before.
Also fix the SIZE_MAX macro to be similarly safe, if we are forced
to provide a definition for that. The test added in commit 2e70d6b5e
happens to do what we want even with the hack "(size_t) -1" definition,
but we could easily get burnt on other tests in future.
Back-patch to all supported branches, like the previous commits.
Discussion: https://postgr.es/m/15883.1504278595@sss.pgh.pa.us
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Pre-C99 platforms may lack <stdint.h> and thereby SIZE_MAX. We have
a couple of places using the hack "(size_t) -1" as a fallback, but
it wasn't universally available; which means the code added in commit
2e70d6b5e fails to compile everywhere. Move that hack to c.h so that
we can rely on having SIZE_MAX everywhere.
Per discussion, it'd be a good idea to make the macro's value safe
for use in #if-tests, but that will take a bit more work. This is
just a quick expedient to get the buildfarm green again.
Back-patch to all supported branches, like the previous commit.
Discussion: https://postgr.es/m/15883.1504278595@sss.pgh.pa.us
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Michael Paquier, reviewed by Fabien Coelho
Discussion: http://postgr.es/m/CAB7nPqQcYWmrm2n-dVaMUhYPKFU_DxQwPuUGuC4ZF+8B=dS5xQ@mail.gmail.com
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Commit 0e141c0fbb211bdd23783afa731e3eef95c9ad7a introduced a mechanism
to reduce contention on ProcArrayLock by having a single process clear
XIDs in the procArray on behalf of multiple processes, reducing the
need to hand the lock around. A previous attempt to introduce a similar
mechanism for CLogControlLock in ccce90b398673d55b0387b3de66639b1b30d451b
crashed and burned, but the design problem which resulted in those
failures is believed to have been corrected in this version.
Amit Kapila, with some cosmetic changes by me. See the previous commit
message for additional credits.
Discussion: http://postgr.es/m/CAA4eK1KudxzgWhuywY_X=yeSAhJMT4DwCjroV5Ay60xaeB2Eew@mail.gmail.com
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The original code had a race condition because it never ensured the
standby was caught up before proceeding; add a wait similar to every
other place that does this.
Author: Michaël Paquier
Discussion: https://postgr.es/m/CAB7nPqTm9p+LCm1mVJYvgpwagRK+uibT-pKq0O2-paOWxT62jw@mail.gmail.com
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Do for replication origins what the previous commit did for replication
slots: restore the original behavior of replication origin drop to raise
an error rather than blocking, because users might be depending on the
original behavior. Maintain the blocking behavior when invoked
internally from logical replication subscription handling.
Discussion: https://postgr.es/m/20170830133922.tlpo3lgfejm4n2cs@alvherre.pgsql
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Wait for slot to become inactive before continuing.
Author: Petr Jelinek
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Commit 9915de6c1cb2 changed the default behavior of
DROP_REPLICATION_SLOT so that it would wait until any session holding
the slot active would release it, instead of raising an error. But
users are already depending on the original behavior, so revert to it by
default and add a WAIT option to invoke the new behavior.
Per complaint from Simone Gotti, in
Discussion: https://postgr.es/m/CAEvsy6Wgdf90O6pUvg2wSVXL2omH5OPC-38OD4Zzgk-FXavj3Q@mail.gmail.com
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Bugs introduced by commit 81c5e46c490e2426db243eada186995da5bb0ba7
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This will be useful for hash partitioning, which needs a way to seed
the hash functions to avoid problems such as a hash index on a hash
partitioned table clumping all values into a small portion of the
bucket space; it's also useful for anything that wants a 64-bit hash
value rather than a 32-bit hash value.
Just in case somebody wants a 64-bit hash value that is compatible
with the existing 32-bit hash values, make the low 32-bits of the
64-bit hash value match the 32-bit hash value when the seed is 0.
Robert Haas and Amul Sul
Discussion: http://postgr.es/m/CA+Tgmoafx2yoJuhCQQOL5CocEi-w_uG4S2xT0EtgiJnPGcHW3g@mail.gmail.com
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Rescanning a GatherMerge led to leaking some memory in the executor's
query-lifespan context, because most of the node's working data structures
were simply abandoned and rebuilt from scratch. In practice, this might
never amount to much, given the cost of relaunching worker processes ---
but it's still pretty messy, so let's fix it.
We can rearrange things so that the tuple arrays are simply cleared and
reused, and we don't need to rebuild the TupleTableSlots either, just
clear them. One small complication is that because we might get a
different number of workers on each iteration, we can't keep the old
convention that the leader's gm_slots[] entry is the last one; the leader
might clobber a TupleTableSlot that we need for a worker in a future
iteration. Hence, adjust the logic so that the leader has slot 0 always,
while the active workers have slots 1..n.
Back-patch to v10 to keep all the existing versions of nodeGatherMerge.c
in sync --- because of the renumbering of the slots, there would otherwise
be a very large risk that any future backpatches in this module would
introduce bugs.
Discussion: https://postgr.es/m/8670.1504192177@sss.pgh.pa.us
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Previously, we expanded the inheritance hierarchy in the order in
which find_all_inheritors had locked the tables, but that turns out
to block quite a bit of useful optimization. For example, a
partition-wise join can't count on two tables with matching bounds
to get expanded in the same order.
Where possible, this change results in expanding partitioned tables in
*bound* order. Bound order isn't well-defined for a list-partitioned
table with a null-accepting partition or for a list-partitioned table
where the bounds for a single partition are interleaved with other
partitions. However, when expansion in bound order is possible, it
opens up further opportunities for optimization, such as
strength-reducing MergeAppend to Append when the expansion order
matches the desired sort order.
Patch by me, with cosmetic revisions by Ashutosh Bapat.
Discussion: http://postgr.es/m/CA+TgmoZrKj7kEzcMSum3aXV4eyvvbh9WD=c6m=002WMheDyE3A@mail.gmail.com
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The logic around shm_mq_detach was a few bricks shy of a load, because
(contrary to the comments for shm_mq_attach) all it did was update the
shared shm_mq state. That left us leaking a bit of process-local
memory, but much worse, the on_dsm_detach callback for shm_mq_detach
was still armed. That means that whenever we ultimately detach from
the DSM segment, we'd run shm_mq_detach again for already-detached,
possibly long-dead queues. This accidentally fails to fail today,
because we only ever re-use a shm_mq's memory for another shm_mq, and
multiple detach attempts on the last such shm_mq are fairly harmless.
But it's gonna bite us someday, so let's clean it up.
To do that, change shm_mq_detach's API so it takes a shm_mq_handle
not the underlying shm_mq. This makes the callers simpler in most
cases anyway. Also fix a few places in parallel.c that were just
pfree'ing the handle structs rather than doing proper cleanup.
Back-patch to v10 because of the risk that the revenant shm_mq_detach
callbacks would cause a live bug sometime. Since this is an API
change, it's too late to do it in 9.6. (We could make a variant
patch that preserves API, but I'm not excited enough to do that.)
Discussion: https://postgr.es/m/8670.1504192177@sss.pgh.pa.us
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Make sure that rescans of parallel indexscans are tested.
Per code coverage report.
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PG_MODULE_MAGIC has been around since 8.2, with 8.1 long since in EOL,
so remove the mention of #ifdef guards for compiling against pre-8.2
sources from the documentation.
Author: Daniel Gustafsson <daniel@yesql.se>
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Comment the fields of GatherMergeState, and organize them a bit more
sensibly. Comment GMReaderTupleBuffer more usefully too. Improve
assorted other comments that were obsolete or just not very good English.
Get rid of the use of a GMReaderTupleBuffer for the leader process;
that was confusing, since only the "done" field was used, and that
in a way redundant with need_to_scan_locally.
In gather_merge_init, avoid calling load_tuple_array for
already-known-exhausted workers. I'm not sure if there's a live bug there,
but the case is unlikely to be well tested due to timing considerations.
Remove some useless code, such as duplicating the tts_isempty test done by
TupIsNull.
Remove useless initialization of ps.qual, replacing that with an assertion
that we have no qual to check. (If we did, the code would fail to check
it.)
Avoid applying heap_copytuple to a null tuple. While that fails to crash,
it's confusing and it makes the code less legible not more so IMO.
Propagate a couple of these changes into nodeGather.c, as well.
Back-patch to v10, partly because of the possibility that the
gather_merge_init change is fixing a live bug, but mostly to keep
the branches in sync to ease future bug fixes.
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Previously, the parallel executor logic did reinitialization of shared
state within the ExecReScan code for parallel-aware scan nodes. This is
problematic, because it means that the ExecReScan call has to occur
synchronously (ie, during the parent Gather node's ReScan call). That is
swimming very much against the tide so far as the ExecReScan machinery is
concerned; the fact that it works at all today depends on a lot of fragile
assumptions, such as that no plan node between Gather and a parallel-aware
scan node is parameterized. Another objection is that because ExecReScan
might be called in workers as well as the leader, hacky extra tests are
needed in some places to prevent unwanted shared-state resets.
Hence, let's separate this code into two functions, a ReInitializeDSM
call and the ReScan call proper. ReInitializeDSM is called only in
the leader and is guaranteed to run before we start new workers.
ReScan is returned to its traditional function of resetting only local
state, which means that ExecReScan's usual habits of delaying or
eliminating child rescan calls are safe again.
As with the preceding commit 7df2c1f8d, it doesn't seem to be necessary
to make these changes in 9.6, which is a good thing because the FDW and
CustomScan APIs are impacted.
Discussion: https://postgr.es/m/CAA4eK1JkByysFJNh9M349u_nNjqETuEnY_y1VUc_kJiU0bxtaQ@mail.gmail.com
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Revert the reversion commits a20aac890 and 9b644745c. In the wake of
commit 7df2c1f8d, we should get stable buildfarm results from this test;
if not, I'd like to know sooner not later.
Discussion: https://postgr.es/m/CAA4eK1JkByysFJNh9M349u_nNjqETuEnY_y1VUc_kJiU0bxtaQ@mail.gmail.com
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The ExecReScan machinery contains various optimizations for postponing
or skipping rescans of plan subtrees; for example a HashAgg node may
conclude that it can re-use the table it built before, instead of
re-reading its input subtree. But that is wrong if the input contains
a parallel-aware table scan node, since the portion of the table scanned
by the leader process is likely to vary from one rescan to the next.
This explains the timing-dependent buildfarm failures we saw after
commit a2b70c89c.
The established mechanism for showing that a plan node's output is
potentially variable is to mark it as depending on some runtime Param.
Hence, to fix this, invent a dummy Param (one that has a PARAM_EXEC
parameter number, but carries no actual value) associated with each Gather
or GatherMerge node, mark parallel-aware nodes below that node as dependent
on that Param, and arrange for ExecReScanGather[Merge] to flag that Param
as changed whenever the Gather[Merge] node is rescanned.
This solution breaks an undocumented assumption made by the parallel
executor logic, namely that all rescans of nodes below a Gather[Merge]
will happen synchronously during the ReScan of the top node itself.
But that's fundamentally contrary to the design of the ExecReScan code,
and so was doomed to fail someday anyway (even if you want to argue
that the bug being fixed here wasn't a failure of that assumption).
A follow-on patch will address that issue. In the meantime, the worst
that's expected to happen is that given very bad timing luck, the leader
might have to do all the work during a rescan, because workers think
they have nothing to do, if they are able to start up before the eventual
ReScan of the leader's parallel-aware table scan node has reset the
shared scan state.
Although this problem exists in 9.6, there does not seem to be any way
for it to manifest there. Without GatherMerge, it seems that a plan tree
that has a rescan-short-circuiting node below Gather will always also
have one above it that will short-circuit in the same cases, preventing
the Gather from being rescanned. Hence we won't take the risk of
back-patching this change into 9.6. But v10 needs it.
Discussion: https://postgr.es/m/CAA4eK1JkByysFJNh9M349u_nNjqETuEnY_y1VUc_kJiU0bxtaQ@mail.gmail.com
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Adding more than 1 billion rows to a PGresult would overflow its ntups and
tupArrSize fields, leading to client crashes. It'd be desirable to use
wider fields on 64-bit machines, but because all of libpq's external APIs
use plain "int" for row counters, that's going to be hard to accomplish
without an ABI break. Given the lack of complaints so far, and the general
pain that would be involved in using such huge PGresults, let's settle for
just preventing the overflow and reporting a useful error message if it
does happen. Also, for a couple more lines of code we can increase the
threshold of trouble from INT_MAX/2 to INT_MAX rows.
To do that, refactor pqAddTuple() to allow returning an error message that
replaces the default assumption that it failed because of out-of-memory.
Along the way, fix PQsetvalue() so that it reports all failures via
pqInternalNotice(). It already did so in the case of bad field number,
but neglected to report anything for other error causes.
Because of the potential for crashes, this seems like a back-patchable
bug fix, despite the lack of field reports.
Michael Paquier, per a complaint from Igor Korot.
Discussion: https://postgr.es/m/CA+FnnTxyLWyjY1goewmJNxC==HQCCF4fKkoCTa9qR36oRAHDPw@mail.gmail.com
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