This patch makes a number of interrelated changes to reduce the overhead
involved in creating/deleting memory contexts. The key ideas are:
* Include the AllocSetContext header of an aset.c context in its first
malloc request, rather than allocating it separately in TopMemoryContext.
This means that we now always create an initial or "keeper" block in an
aset, even if it never receives any allocation requests.
* Create freelists in which we can save and recycle recently-destroyed
asets (this idea is due to Robert Haas).
* In the common case where the name of a context is a constant string,
just store a pointer to it in the context header, rather than copying
the string.
The first change eliminates a palloc/pfree cycle per context, and
also avoids bloat in TopMemoryContext, at the price that creating
a context now involves a malloc/free cycle even if the context never
receives any allocations. That would be a loser for some common
usage patterns, but recycling short-lived contexts via the freelist
eliminates that pain.
Avoiding copying constant strings not only saves strlen() and strcpy()
overhead, but is an essential part of the freelist optimization because
it makes the context header size constant. Currently we make no
attempt to use the freelist for contexts with non-constant names.
(Perhaps someday we'll need to think harder about that, but in current
usage, most contexts with custom names are long-lived anyway.)
The freelist management in this initial commit is pretty simplistic,
and we might want to refine it later --- but in common workloads that
will never matter because the freelists will never get full anyway.
To create a context with a non-constant name, one is now required to
call AllocSetContextCreateExtended and specify the MEMCONTEXT_COPY_NAME
option. AllocSetContextCreate becomes a wrapper macro, and it includes
a test that will complain about non-string-literal context name
parameters on gcc and similar compilers.
An unfortunate side effect of making AllocSetContextCreate a macro is
that one is now *required* to use the size parameter abstraction macros
(ALLOCSET_DEFAULT_SIZES and friends) with it; the pre-9.6 habit of
writing out individual size parameters no longer works unless you
switch to AllocSetContextCreateExtended.
Internally to the memory-context-related modules, the context creation
APIs are simplified, removing the rather baroque original design whereby
a context-type module called mcxt.c which then called back into the
context-type module. That saved a bit of code duplication, but not much,
and it prevented context-type modules from exercising control over the
allocation of context headers.
In passing, I converted the test-and-elog validation of aset size
parameters into Asserts to save a few more cycles. The original thought
was that callers might compute size parameters on the fly, but in practice
nobody does that, so it's useless to expend cycles on checking those
numbers in production builds.
Also, mark the memory context method-pointer structs "const",
just for cleanliness.
Discussion: https://postgr.es/m/2264.1512870796@sss.pgh.pa.us
port.h redirects isnan() to _isnan() on windows, which in turn is
provided by float.h rather than math.h. Therefore include the latter
as well.
Per buildfarm.
A previous commit added inline functions that provide fast(er) and
correct overflow checks for signed integer math. Use them in a
significant portion of backend code. There's more to touch in both
backend and frontend code, but these were the easily identifiable
cases.
The old overflow checks are noticeable in integer heavy workloads.
A secondary benefit is that getting rid of overflow checks that rely
on signed integer overflow wrapping around, will allow us to get rid
of -fwrapv in the future. Which in turn slows down other code.
Author: Andres Freund
Discussion: https://postgr.es/m/20171024103954.ztmatprlglz3rwke@alap3.anarazel.de
Commit 8b304b8b72 removed replacement
selection, but left behind this comment text. The optimization to
which the comment refers is not relevant without replacement
selection, because if we had so few tuples as to require only one
tape, we would have just completed the sort in memory.
Peter Geoghegan
Discussion: http://postgr.es/m/CAH2-WznqupLA8CMjp+vqzoe0yXu0DYYbQSNZxmgN76tLnAOZ_w@mail.gmail.com
I noticed that _SPI_execute_plan initially sets spierrcontext.arg = NULL,
and only fills it in some time later. If an error were to happen in
between, _SPI_error_callback would try to dereference the null pointer.
This is unlikely --- there's not much between those points except
push-snapshot calls --- but it's clearly not impossible. Tweak the
callback to do nothing if the pointer isn't set yet.
It's been like this for awhile, so back-patch to all supported branches.
Those cases currently crash and supporting them is more work then
originally thought, so we'll just prohibit these scenarios for now.
Author: Michael Paquier <michael.paquier@gmail.com>
Reviewed-by: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Reported-by: Мансур Галиев <gomer94@yandex.ru>
Bug: #14866
A COPY into a table should apply identity sequence values just like it
does for ordinary defaults. This was previously forgotten, leading to
null values being inserted, which in turn would fail because identity
columns have not-null constraints.
Author: Michael Paquier <michael.paquier@gmail.com>
Reported-by: Steven Winfield <steven.winfield@cantabcapital.com>
Bug: #14952
When a worker is flagged as BGW_NEVER_RESTART and we fail to start it,
or if it is not marked BGW_NEVER_RESTART but is terminated before
startup succeeds, what BgwHandleStatus should be reported? The
previous code really hadn't considered this possibility (as indicated
by the comments which ignore it completely) and would typically return
BGWH_NOT_YET_STARTED, but that's not a good answer, because then
there's no way for code using GetBackgroundWorkerPid() to tell the
difference between a worker that has not started but will start
later and a worker that has not started and will never be started.
So, when this case happens, return BGWH_STOPPED instead. Update the
comments to reflect this.
The preceding fix by itself is insufficient to fix the problem,
because the old code also didn't send a notification to the process
identified in bgw_notify_pid when startup failed. That might've
been technically correct under the theory that the status of the
worker was BGWH_NOT_YET_STARTED, because the status would indeed not
change when the worker failed to start, but now that we're more
usefully reporting BGWH_STOPPED, a notification is needed.
Without these fixes, code which starts background workers and then
uses the recommended APIs to wait for those background workers to
start would hang indefinitely if the postmaster failed to fork a
worker.
Amit Kapila and Robert Haas
Discussion: http://postgr.es/m/CAA4eK1KDfKkvrjxsKJi3WPyceVi3dH1VCkbTJji2fuwKuB=3uw@mail.gmail.com
When we create an Append node, we can spread out the workers over the
subplans instead of piling on to each subplan one at a time, which
should typically be a bit more efficient, both because the startup
cost of any plan executed entirely by one worker is paid only once and
also because of reduced contention. We can also construct Append
plans using a mix of partial and non-partial subplans, which may allow
for parallelism in places that otherwise couldn't support it.
Unfortunately, this patch doesn't handle the important case of
parallelizing UNION ALL by running each branch in a separate worker;
the executor infrastructure is added here, but more planner work is
needed.
Amit Khandekar, Robert Haas, Amul Sul, reviewed and tested by
Ashutosh Bapat, Amit Langote, Rafia Sabih, Amit Kapila, and
Rajkumar Raghuwanshi.
Discussion: http://postgr.es/m/CAJ3gD9dy0K_E8r727heqXoBmWZ83HwLFwdcaSSmBQ1+S+vRuUQ@mail.gmail.com
When a Gather or Gather Merge node is started and stopped multiple
times, the old code wouldn't reset the shared state between executions,
potentially resulting in dramatically inflated instrumentation data
for nodes beneath it. (The per-worker instrumentation ended up OK,
I think, but the overall totals were inflated.)
Report by hubert depesz lubaczewski. Analysis and fix by Amit Kapila,
reviewed and tweaked a bit by me.
Discussion: http://postgr.es/m/20171127175631.GA405@depesz.com
If a hash join appears in a parallel query, there may be no hash table
available for explain.c to inspect even though a hash table may have
been built in other processes. This could happen either because
parallel_leader_participation was set to off or because the leader
happened to hit the end of the outer relation immediately (even though
the complete relation is not empty) and decided not to build the hash
table.
Commit bf11e7ee introduced a way for workers to exchange
instrumentation via the DSM segment for Sort nodes even though they
are not parallel-aware. This commit does the same for Hash nodes, so
that explain.c has a way to find instrumentation data from an
arbitrary participant that actually built the hash table.
Author: Thomas Munro
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/CAEepm%3D3DUQC2-z252N55eOcZBer6DPdM%3DFzrxH9dZc5vYLsjaA%40mail.gmail.com
Previously, this code just reported such problems at LOG level and kept
going. The problem with this approach is that transient failures (e.g.,
ENFILE) could prevent us from resetting unlogged relations to empty,
yet allow recovery to appear to complete successfully. That seems like
a data corruption hazard large enough to treat such problems as reasons
to fail startup.
For the same reason, treat unlink failures for unlogged files as hard
errors not just LOG messages. It's a little odd that we did it like that
when file-level errors in other steps (copy_file, fsync_fname) are ERRORs.
The sole case that I left alone is that ENOENT failure on a tablespace
(not database) directory is not an error, though it will now be logged
rather than just silently ignored. This is to cover the scenario where
a previous DROP TABLESPACE removed the tablespace directory but failed
before removing the pg_tblspc symlink. I'm not sure that that's very
likely in practice, but that seems like the only real excuse for the
old behavior here, so let's allow for it. (As coded, this will also
allow ENOENT on $PGDATA/base/. But since we'll fail soon enough if
that's gone, I don't think we need to complicate this code by
distinguishing that from a true tablespace case.)
Discussion: https://postgr.es/m/21040.1512418508@sss.pgh.pa.us
do_pg_start_backup() expects its callers to pass in an open DIR pointer
for the pg_tblspc directory, but there's no apparent advantage in that.
It complicates the callers without adding any flexibility, and there's no
robustness advantage, since we surely have to be prepared for errors during
the scan of pg_tblspc anyway. In fact, by holding an extra kernel resource
during operations like the preliminary checkpoint, we might be making
things a fraction more failure-prone not less. Hence, remove that argument
and open the directory just for the duration of the actual scan.
Discussion: https://postgr.es/m/28752.1512413887@sss.pgh.pa.us
Modify this function and its subsidiaries so that syscall failures are
reported via ereport(LOG), rather than silently ignored as before.
We don't want to throw a hard ERROR, as that would prevent database
startup, and getting rid of leftover temporary files is not important
enough for that. On the other hand, not reporting trouble at all
seems like an odd choice not in line with current project norms,
especially since any failure here is quite unexpected.
On the same reasoning, adjust these functions' AllocateDir/ReadDir calls
so that failure to scan a directory results in LOG not ERROR. I also
removed the previous practice of silently ignoring ENOENT failures during
directory opens --- there are some corner cases where that could happen
given a previous database crash, but that seems like a bad excuse for
ignoring a condition that isn't expected in most cases. A LOG message
during postmaster start seems OK in such situations, and better than
no output at all.
In passing, make RemovePgTempRelationFiles' test for "is the file name
all digits" look more like the way it's done elsewhere.
Discussion: https://postgr.es/m/19907.1512402254@sss.pgh.pa.us
This patch fixes a couple of low-probability bugs that could lead to
reporting an irrelevant errno value (and hence possibly a wrong SQLSTATE)
concerning directory-open or file-open failures. It also fixes places
where we took shortcuts in reporting such errors, either by using elog
instead of ereport or by using ereport but forgetting to specify an
errcode. And it eliminates a lot of just plain redundant error-handling
code.
In service of all this, export fd.c's formerly-static function
ReadDirExtended, so that external callers can make use of the coding
pattern
dir = AllocateDir(path);
while ((de = ReadDirExtended(dir, path, LOG)) != NULL)
if they'd like to treat directory-open failures as mere LOG conditions
rather than errors. Also fix FreeDir to be a no-op if we reach it
with dir == NULL, as such a coding pattern would cause.
Then, remove code at many call sites that was throwing an error or log
message for AllocateDir failure, as ReadDir or ReadDirExtended can handle
that job just fine. Aside from being a net code savings, this gets rid of
a lot of not-quite-up-to-snuff reports, as mentioned above. (In some
places these changes result in replacing a custom error message such as
"could not open tablespace directory" with more generic wording "could not
open directory", but it was agreed that the custom wording buys little as
long as we report the directory name.) In some other call sites where we
can't just remove code, change the error reports to be fully
project-style-compliant.
Also reorder code in restoreTwoPhaseData that was acquiring a lock
between AllocateDir and ReadDir; in the unlikely but surely not
impossible case that LWLockAcquire changes errno, AllocateDir failures
would be misreported. There is no great value in opening the directory
before acquiring TwoPhaseStateLock, so just do it in the other order.
Also fix CheckXLogRemoved to guarantee that it preserves errno,
as quite a number of call sites are implicitly assuming. (Again,
it's unlikely but I think not impossible that errno could change
during a SpinLockAcquire. If so, this function was broken for its
own purposes as well as breaking callers.)
And change a few places that were using not-per-project-style messages,
such as "could not read directory" when "could not open directory" is
more correct.
Back-patch the exporting of ReadDirExtended, in case we have occasion
to back-patch some fix that makes use of it; it's not needed right now
but surely making it global is pretty harmless. Also back-patch the
restoreTwoPhaseData and CheckXLogRemoved fixes. The rest of this is
essentially cosmetic and need not get back-patched.
Michael Paquier, with a bit of additional work by me
Discussion: https://postgr.es/m/CAB7nPqRpOCxjiirHmebEFhXVTK7V5Jvw4bz82p7Oimtsm3TyZA@mail.gmail.com
Hopefully, the additional logging will help avoid confusion that
could otherwise result.
Nathan Bossart, reviewed by Michael Paquier, Fabrízio Mello, and me
There's no good reason that the multicolumn stats stuff shouldn't work on
booleans. But it looked only for "Var = pseudoconstant" clauses, and it
will seldom find those for boolean Vars, since earlier phases of planning
will fold "boolvar = true" or "boolvar = false" to just "boolvar" or
"NOT boolvar" respectively. Improve dependencies_clauselist_selectivity()
to recognize such clauses as equivalent to equality restrictions.
This fixes a failure of the extended stats mechanism to apply in a case
reported by Vitaliy Garnashevich. It's not a complete solution to his
problem because the bitmap-scan costing code isn't consulting extended
stats where it should, but that's surely an independent issue.
In passing, improve some comments, get rid of a NumRelids() test that's
redundant with the preceding bms_membership() test, and fix
dependencies_clauselist_selectivity() so that estimatedclauses actually
is a pure output argument as stated by its API contract.
Back-patch to v10 where this code was introduced.
Discussion: https://postgr.es/m/73a4936d-2814-dc08-ed0c-978f76f435b0@gmail.com
Before commit 6b65a7fe62, tqueue.c could
perform tuple remapping and thus leak memory, which is why commit
af33039317 made TupleQueueReaderNext
run in a short-lived context. Now, however, tqueue.c has been reduced
to a shadow of its former self, and there shouldn't be any chance of
leaks any more. Accordingly, remove some tuple copying and memory
context manipulation to speed up processing.
Patch by me, reviewed by Amit Kapila. Some testing by Rafia Sabih.
Discussion: http://postgr.es/m/CAA4eK1LSDydwrNjmYSNkfJ3ZivGSWH9SVswh6QpNzsMdj_oOQA@mail.gmail.com
Without this, when partdesc->nparts == 0, we end up calling
ExecBuildSlotPartitionKeyDescription without initializing values
and isnull.
Reported by Coverity via Michael Paquier. Patch by Michael Paquier,
reviewed and revised by Amit Langote.
Discussion: http://postgr.es/m/CAB7nPqQ3mwkdMoPY-ocgTpPnjd8TKOadMxdTtMLvEzF8480Zfg@mail.gmail.com
We need to check whether the channel-binding flag encoded in the
client-final-message is the same one sent in the client-first-message.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
This adds a new object type "procedure" that is similar to a function
but does not have a return type and is invoked by the new CALL statement
instead of SELECT or similar. This implementation is aligned with the
SQL standard and compatible with or similar to other SQL implementations.
This commit adds new commands CALL, CREATE/ALTER/DROP PROCEDURE, as well
as ALTER/DROP ROUTINE that can refer to either a function or a
procedure (or an aggregate function, as an extension to SQL). There is
also support for procedures in various utility commands such as COMMENT
and GRANT, as well as support in pg_dump and psql. Support for defining
procedures is available in all the languages supplied by the core
distribution.
While this commit is mainly syntax sugar around existing functionality,
future features will rely on having procedures as a separate object
type.
Reviewed-by: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>
Put the unique path in the same context as the owning RelOptInfo, rather
than the toplevel planner context. This is how this function worked
originally, but commit f41803bb39
changed it without explanation. mark_dummy_rel adopted the older (or
newer?) technique in commit eca75a12a2,
which also featured a much better explanation of why it is correct.
So, switch back to that technique here, with the same explanation
given there.
Although this fixes a possible memory leak when GEQO is in use, the
leak is minor and probably nobody cares, so no back-patch.
Ashutosh Bapat, reviewed by Tom Lane and by me
Discussion: http://postgr.es/m/CAFjFpRcXkHHrXyD9BCvkgGJV4TnHG2SWJ0PhJfrDu3NAcQvh7g@mail.gmail.com
Previously, this function estimated the selectivity as 1 minus eqjoinsel()
for the negator equality operator, regardless of join type (I think there
was an expectation that eqjoinsel would handle the join type). But
actually this is completely wrong for semijoin cases: the fraction of the
LHS that has a non-matching row is not one minus the fraction of the LHS
that has a matching row. In reality a semijoin with <> will nearly always
succeed: it can only fail when the RHS is empty, or it contains a single
distinct value that is equal to the particular LHS value, or the LHS value
is null. The only one of those things we should have much confidence in
estimating is the fraction of LHS values that are null, so let's just take
the selectivity as 1 minus outer nullfrac.
Per coding convention, antijoin should be estimated the same as semijoin.
Arguably this is a bug fix, but in view of the lack of field complaints
and the risk of destabilizing plans, no back-patch.
Thomas Munro, reviewed by Ashutosh Bapat
Discussion: https://postgr.es/m/CAEepm=270ze2hVxWkJw-5eKzc3AB4C9KpH3L2kih75R5pdSogg@mail.gmail.com
Provide support for dynamic or static parties of processes to wait for
all processes to reach point in the code before continuing.
This is similar to the mechanism of the same name in POSIX threads and
MPI, though has explicit phasing and dynamic party support like the
Java core library's Phaser.
This will be used by an upcoming patch adding support for parallel
hash joins.
Author: Thomas Munro
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/CAEepm=2_y7oi01OjA_wLvYcWMc9_d=LaoxrY3eiROCZkB_qakA@mail.gmail.com
This will be used by pending patches to improve partition pruning.
Amit Langote and Kyotaro Horiguchi, per a suggestion from David
Rowley. Review and testing of the larger patch set of which this is a
part by Ashutosh Bapat, David Rowley, Dilip Kumar, Jesper Pedersen,
Rajkumar Raghuwanshi, Beena Emerson, Amul Sul, and Kyotaro Horiguchi.
Discussion: http://postgr.es/m/098b9c71-1915-1a2a-8d52-1a7a50ce79e8@lab.ntt.co.jp
Commit d466335064 changed things so
that shm_toc_lookup would fail with an error rather than silently
returning NULL in the hope that such failures would be reported
in a useful way rather than via a system crash. However, it
overlooked the fact that the lookup of PARALLEL_KEY_ERROR_QUEUE
in ReinitializeParallelDSM is expected to fail when no DSM segment
was created in the first place; in that case, we end up with a
backend-private memory segment that still contains an entry for
PARALLEL_KEY_FIXED but no others. Consequently a benign failure
to initialize parallelism can escalate into an elog(ERROR);
repair.
Discussion: http://postgr.es/m/CA+Tgmob8LFw55DzH1QEREpBEA9RJ_W_amhBFCVZ6WMwUhVpOqg@mail.gmail.com
If we have a plan that uses parallelism but are unable to execute it
using parallelism, for example due to a lack of available DSM
segments, then the EState's es_query_dsa will be NULL. Parallel
bitmap heap scan needs to fall back to a non-parallel scan in such
cases.
Patch by me, reviewed by Dilip Kumar
Discussion: http://postgr.es/m/CAEepm=0kADK5inNf_KuemjX=HQ=PuTP0DykM--fO5jS5ePVFEA@mail.gmail.com
Non-default range partitions have a constraint which include null
tests, and both default and non-default list partitions also have a
constraint which includes null tests, but for some reason this was
missed for default range partitions. This could cause the partition
constraint to evaluate to false for rows that were (correctly) routed
to that partition by insert tuple routing, which could in turn
cause constraint exclusion to prune the default partition in cases
where it should not.
Amit Langote, reviewed by Kyotaro Horiguchi
Discussion: http://postgr.es/m/ba7aaeb1-4399-220e-70b4-62eade1522d0@lab.ntt.co.jp
Robert Haas
Tom Lane
Peter Eisentraut
Andres Freund
Magnus Hagander
Alvaro Herrera