Up to now, there's been hard-wired assumptions that normal aggregates'
final functions never modify their transition states, while ordered-set
aggregates' final functions always do. This has always been a bit
limiting, and in particular it's getting in the way of improving the
built-in ordered-set aggregates to allow merging of transition states.
Therefore, let's introduce catalog and CREATE AGGREGATE infrastructure
that lets the finalfn's behavior be declared explicitly.
There are now three possibilities for the finalfn behavior: it's purely
read-only, it trashes the transition state irrecoverably, or it changes
the state in such a way that no more transfn calls are possible but the
state can still be passed to other, compatible finalfns. There are no
examples of this third case today, but we'll shortly make the built-in
OSAs act like that.
This change allows user-defined aggregates to explicitly disclaim support
for use as window functions, and/or to prevent transition state merging,
if their implementations cannot handle that. While it was previously
possible to handle the window case with a run-time error check, there was
not any way to prevent transition state merging, which in retrospect is
something commit 804163bc2 should have provided for. But better late
than never.
In passing, split out pg_aggregate.c's extern function declarations into
a new header file pg_aggregate_fn.h, similarly to what we've done for
some other catalog headers, so that pg_aggregate.h itself can be safe
for frontend files to include. This lets pg_dump use the symbolic
names for relevant constants.
Discussion: https://postgr.es/m/4834.1507849699@sss.pgh.pa.us
In c3d9a66024, the genhtml --prefix option
was removed to get slightly better behavior for vpath builds. genhtml
would then automatically pick a suitable prefix. However, for non-vpath
builds, this makes the coverage output dependent on the length of the
path where the source code happens to be, leading to confusingly
arbitrary results. So put the --prefix option back for non-vpath
builds.
A few command line options accepted by pg_regress were not being output
by help(), including --help itself. Add that one, as well as --version
and --bindir, and the corresponding short options for the first two.
We could consider this for backpatching, but it did not seem worthwhile
and no one else advocated for it, so apply only to master for now.
Author: Joe Conway
Reviewed-By: Tom Lane
Discussion: https://postgr.es/m/dd519469-06d7-2662-83ef-c926f6c4f0f1%40joeconway.com
The following are the individual improvements:
1) Avoidance of FunctionCallInfo based function calls, replaced by
more efficient functions with a native C argument interface.
2) Don't extract columns from a cache entry's tuple whenever matching
entries - instead store them as a Datum array. This also allows to
get rid of having to build dummy tuples for negative & list
entries, and of a hack for dealing with cstring vs. text weirdness.
3) Reorder members of catcache.h struct, so imortant entries are more
likely to be on one cacheline.
4) Allowing the compiler to specialize critical SearchCatCache for a
specific number of attributes allows to unroll loops and avoid
other nkeys dependant initialization.
5) Only initializing the ScanKey when necessary, i.e. catcache misses,
greatly reduces cache unnecessary cpu cache misses.
6) Split of the cache-miss case from the hash lookup, reducing stack
allocations etc in the common case.
7) CatCTup and their corresponding heaptuple are allocated in one
piece.
This results in making cache lookups themselves roughly three times as
fast - full-system benchmarks obviously improve less than that.
I've also evaluated further techniques:
- replace open coded hash with simplehash - the list walk right now
shows up in profiles. Unfortunately it's not easy to do so safely as
an entry's memory location can change at various times, which
doesn't work well with the refcounting and cache invalidation.
- Cacheline-aligning CatCTup entries - helps some with performance,
but the win isn't big and the code for it is ugly, because the
tuples have to be freed as well.
- add more proper functions, rather than macros for
SearchSysCacheCopyN etc., but right now they don't show up in
profiles.
The reason the macro wrapper for syscache.c/h have to be changed,
rather than just catcache, is that doing otherwise would require
exposing the SysCache array to the outside. That might be a good idea
anyway, but it's for another day.
Author: Andres Freund
Reviewed-By: Robert Haas
Discussion: https://postgr.es/m/20170914061207.zxotvyopetm7lrrp@alap3.anarazel.de
Forcing a function not to be inlined can be useful if it's the
slow-path of a performance critical function, or should be visible in
profiles to allow for proper cost attribution.
Author: Andres Freund
Discussion: https://postgr.es/m/20170914061207.zxotvyopetm7lrrp@alap3.anarazel.de
Per buildfarm animal Hornet and followup manual testing by Noah Misch,
it appears xlc miscompiles code using "restrict" in at least some
cases. Allow disabling restrict usage with FORCE_DISABLE_RESTRICT=yes
in template files, and do so for aix/xlc.
Author: Andres Freund and Tom Lane
Discussion: https://postgr.es/m/1820.1507918762@sss.pgh.pa.us
If a Parallel Bitmap Heap scan's chain of leftmost descendents
includes a BitmapOr whose first child is a BitmapAnd, the prior coding
would mistakenly create a non-shared TIDBitmap and then try to perform
shared iteration.
Report by Tomas Vondra. Patch by Dilip Kumar.
Discussion: http://postgr.es/m/50e89684-8ad9-dead-8767-c9545bafd3b6@2ndquadrant.com
I (tgl) objected to the obscure implementation introduced in commit
1c497fa72. This one seems a bit less action-at-a-distance-y, at the
price of repeating a few lines of code.
Improve the comments about what the function is doing, too.
Amit Khandekar, whacked around a bit more by me
Discussion: https://postgr.es/m/CAJ3gD9egYTyHUH0nTMxm8-1m3RvdqEbaTyGC-CUNtYf7tKNDaQ@mail.gmail.com
In each of the pq_writeintN functions, the three uses of sizeof() should
surely all be consistent. I started out to make them all sizeof(ni),
but on reflection let's make them sizeof(typename) instead. That's more
like our usual style elsewhere, and it's just barely possible that the
failures buildfarm member hornet has shown since 4c119fbcd went in are
caused by the compiler getting confused about sizeof() a parameter that
it's optimizing away.
In passing, improve a couple of comments.
Discussion: https://postgr.es/m/E1e2RML-0002do-Lc@gemulon.postgresql.org
After calling ldap_unbind_s() we probably shouldn't try to use the LDAP
connection again to call ldap_get_option(), even if it failed. The OpenLDAP
man page for ldap_unbind[_s] says "Once it is called, the connection to the
LDAP server is closed, and the ld structure is invalid." Otherwise, as a
general rule we should probably call ldap_unbind() before returning in all
paths to avoid leaking resources. It is unlikely there is any practical
leak problem since failure to authenticate currently results in the backend
exiting soon afterwards.
Author: Thomas Munro
Reviewed-By: Alvaro Herrera, Peter Eisentraut
Discussion: https://postgr.es/m/20170914141205.eup4kxzlkagtmfac%40alvherre.pgsql
Unfortunately using 'restrict' plainly causes problems with MSVC,
which supports restrict only as '__restrict'. Defining 'restrict' to
'__restrict' unfortunately causes a conflict with MSVC's usage of
__declspec(restrict) in headers.
Therefore define pg_restrict to the appropriate keyword instead, and
replace existing usages.
This replaces the temporary workaround introduced in 36b4b91ba0.
Author: Andres Freund
Discussion: https://postgr.es/m/2656.1507830907@sss.pgh.pa.us
The previous convention doesn't lend itself to creating ResultRelInfos
lazily, as we already do in ExecGetTriggerResultRel. This patch
doesn't make anything lazier than before, but the pending patch for
UPDATE tuple routing proposes to do so (and there might be other
opportunities as well).
Amit Khandekar with some adjustments by me.
Discussion: http://postgr.es/m/CA+TgmoYPVP9Lyf6vUFA5DwxS4c--x6LOj2y36BsJaYtp62eXPQ@mail.gmail.com
If we merge the transition calculations for two different aggregates,
it's reasonable to assume that the transition function should not care
which of those Aggref structs it gets from AggGetAggref(). It is not
reasonable to make the same assumption about an aggregate final function,
however. Commit 804163bc2 broke this, as it will pass whichever Aggref
was first associated with the transition state in both cases.
This doesn't create an observable bug so far as the core system is
concerned, because the only existing uses of AggGetAggref() are in
ordered-set aggregates that happen to not pay attention to anything
but the input properties of the Aggref; and besides that, we disabled
sharing of transition calculations for OSAs yesterday. Nonetheless,
if some third-party code were using AggGetAggref() in a normal aggregate,
they would be entitled to call this a bug. Hence, back-patch the fix
to 9.6 where the problem was introduced.
In passing, improve some of the comments about transition state sharing.
Discussion: https://postgr.es/m/CAB4ELO5RZhOamuT9Xsf72ozbenDLLXZKSk07FiSVsuJNZB861A@mail.gmail.com
This ought to work, but the built-in OSAs are not capable of coping,
because their final-functions destructively modify their transition
state (specifically, the contained tuplesort object). That was fine
when those functions were written, but commit 804163bc2 moved the
goalposts without telling orderedsetaggs.c.
We should fix the built-in OSAs to support this, but it will take
a little work, especially if we don't want to sacrifice performance
in the normal non-shared-state case. Given that it took a year after
9.6 release for anyone to notice this bug, we should not prioritize
sharable-state over nonsharable-state performance. And a proper fix
is likely to be more complicated than we'd want to back-patch, too.
Therefore, let's just put in this stop-gap patch to prevent nodeAgg.c
from choosing to use shared state for OSAs. We can revert it in HEAD
when we get a better fix.
Report from Lukas Eder, diagnosis by me, patch by David Rowley.
Back-patch to 9.6 where the problem was introduced.
Discussion: https://postgr.es/m/CAB4ELO5RZhOamuT9Xsf72ozbenDLLXZKSk07FiSVsuJNZB861A@mail.gmail.com
It appears some versions of msvc use __declspec(restrict) in stdlib.h
and subsidiary headers. Including those after defining 'restrict' to
'__restrict' doesn't work. Try to get the buildfarm green to see
whether there's further problems, by including stdlib.h just before
said define.
Apparently MSVC requires a * before a restrict in a variable
declaration, even if the adorned type already is a pointer, just via
typedef.
As reported by buildfarm animal woodlouse.
Author: Andres Freund
Discussion: https://postgr.es/m/20171012001320.4putagiruuehtvb6@alap3.anarazel.de
There's three categories of changes leading to better performance:
- Splitting the per-attribute part of SendRowDescriptionMessage into a
v2 and a v3 version allows avoiding branches for every attribute.
- Preallocating the size of the buffer to be big enough for all
attributes and then using pq_write* avoids unnecessary buffer
size checks & resizing.
- Reusing a persistently allocated StringInfo for all
SendRowDescriptionMessage() invocations avoids repeated allocations
& reallocations.
Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de
This takes advantage of the infrastructure introduced by commit
81c5e46c49 to greatly reduce the
likelihood that two different queries will end up with the same query
ID. It's still possible, of course, but whereas before it the chances
of a collision reached 25% around 50,000 queries, it will now take
more than 3 billion queries.
Backward incompatibility: Because the type exposed at the SQL level is
int8, users may now see negative query IDs in the pg_stat_statements
view (and also, query IDs more than 4 billion, which was the old
limit).
Patch by me, reviewed by Michael Paquier and Peter Geoghegan.
Discussion: http://postgr.es/m/CA+TgmobG_Kp4cBKFmsznUAaM1GWW6hhRNiZC0KjRMOOeYnz5Yw@mail.gmail.com
This avoids newly allocating, and then possibly growing, the
stringbuffer for every row. For wide rows this can substantially
reduce memory allocator overhead, at the price of not immediately
reducing memory usage after outputting an especially wide row.
Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de
There's three prongs to achieve greater efficiency here:
1) Allow reusing a stringbuffer across pq_beginmessage/endmessage,
with the new pq_beginmessage_reuse/endmessage_reuse. This can be
beneficial both because it avoids allocating the initial buffer,
and because it's more likely to already have an correctly sized
buffer.
2) Replacing pq_sendint() with pq_sendint$width() inline
functions. Previously unnecessary and unpredictable branches in
pq_sendint() were needed. Additionally the replacement functions
are implemented more efficiently. pq_sendint is now deprecated, a
separate commit will convert all in-tree callers.
3) Add pq_writeint$width(), pq_writestring(). These rely on sufficient
space in the StringInfo's buffer, avoiding individual space checks
& potential individual resizing. To allow this to be used for
strings, expose mbutil.c's MAX_CONVERSION_GROWTH.
Followup commits will make use of these facilities.
Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de
In a lot of the places having appendBinaryStringInfo() maintain a
trailing NUL byte wasn't actually meaningful, e.g. when appending an
integer which can contain 0 in one of its bytes.
Removing this yields some small speedup, but more importantly will be
more consistent when providing faster variants of pq_sendint etc.
Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de
Will be used in later commits improving performance for a few key
routines where information about aliasing allows for significantly
better code generation.
This allows to use the C99 'restrict' keyword without breaking C89, or
for that matter C++, compilers. If not supported it's defined to be
empty.
Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de
resowner/README contained advice to use a PG_TRY block to restore the
old CurrentResourceOwner value anywhere that that variable is transiently
changed. That advice was only inconsistently followed, however, and
on reflection it seems like unnecessary overhead. We don't bother
with such a convention for transient CurrentMemoryContext changes,
on the grounds that any (sub)transaction abort will start out by
resetting CurrentMemoryContext to what it wants. But the same is
true of CurrentResourceOwner, so there seems no need to treat it
differently.
Hence, remove PG_TRY blocks that exist only to restore CurrentResourceOwner
before re-throwing the error. There are a couple of places that restore
it along with some other actions, and I left those alone; the restore is
probably unnecessary but no noticeable gain will result from removing it.
Discussion: https://postgr.es/m/5236.1507583529@sss.pgh.pa.us
The previous coding in ProcessInterrupts() could lead to
idle_in_transaction_session_timeout being ignored, when
statement_timeout occurred earlier.
The problem was that ProcessInterrupts() would return before
processing the transaction timeout if QueryCancelPending was set while
QueryCancelHoldoffCount != 0 - which is the case when reading new
commands from the client. Ergo when the idle transaction timeout would
hit.
Fix that by removing the early return. Alternatively the transaction
timeout code could have been moved up, but that early return seems
like an issue that could hit other cases too.
Author: Lukas Fittl
Bug: #14821
Discussion:
https://www.postgresql.org/message-id/20170921010956.17345.61461%40wrigleys.postgresql.orghttps://www.postgresql.org/message-id/CAP53PkxQnv3OWJpyNPGJYT62uY=n1=2CF_Lpc6gVOFnc0-gazw@mail.gmail.com
Backpatch: 9.6-, where idle_in_transaction_session_timeout was introduced.
The GRANT reference page, which lists the default privileges for new
objects, failed to mention that USAGE is granted by default for data
types and domains. As a lesser sin, it also did not specify anything
about the initial privileges for sequences, FDWs, foreign servers,
or large objects. Fix that, and add a comment to acldefault() in the
probably vain hope of getting people to maintain this list in future.
Noted by Laurenz Albe, though I editorialized on the wording a bit.
Back-patch to all supported branches, since they all have this behavior.
Discussion: https://postgr.es/m/1507620895.4152.1.camel@cybertec.at
Up to now async.c has used TransactionIdIsInProgress() to detect whether
a notify message's source transaction is still running. However, that
function has a quick-exit path that reports that XIDs before RecentXmin
are no longer running. If a listening backend is doing nothing but
listening, and not running any queries, there is nothing that will advance
its value of RecentXmin. Once 2 billion transactions elapse, the
RecentXmin check causes active transactions to be reported as not running.
If they aren't committed yet according to CLOG, async.c decides they
aborted and discards their messages. The timing for that is a bit tight
but it can happen when multiple backends are sending notifies concurrently.
The net symptom therefore is that a sufficiently-long-surviving
listen-only backend starts to miss some fraction of NOTIFY traffic,
but only under heavy load.
The only function that updates RecentXmin is GetSnapshotData().
A brute-force fix would therefore be to take a snapshot before
processing incoming notify messages. But that would add cycles,
as well as contention for the ProcArrayLock. We can be smarter:
having taken the snapshot, let's use that to check for running
XIDs, and not call TransactionIdIsInProgress() at all. In this
way we reduce the number of ProcArrayLock acquisitions from one
per message to one per notify interrupt; that's the same under
light load but should be a benefit under heavy load. Light testing
says that this change is a wash performance-wise for normal loads.
I looked around for other callers of TransactionIdIsInProgress()
that might be at similar risk, and didn't find any; all of them
are inside transactions that presumably have already taken a
snapshot.
Problem report and diagnosis by Marko Tiikkaja, patch by me.
Back-patch to all supported branches, since it's been like this
since 9.0.
Discussion: https://postgr.es/m/20170926182935.14128.65278@wrigleys.postgresql.org
The previous placement of the fallback implementation in libpgcommon
was problematic, because libpqport functions need strnlen
functionality.
Move replacement into libpgport. Provide strnlen() under its posix
name, instead of pg_strnlen(). Fix stupid configure bug, executing the
test only when compiled with threading support.
Author: Andres Freund
Discussion: https://postgr.es/m/E1e1gR2-0005fB-SI@gemulon.postgresql.org
I noticed the tmp_check subdirectory wasn't getting cleaned up
after a check-world run. Apparently pgxs.mk will only do this
for you if you've defined REGRESS. The only other src/test/modules
Makefile that does not set that is snapshot_too_old, and it
does it like this.
Previously nodeProjectSet only released memory once per input tuple,
rather than once per returned tuple. If the computation of an
individual returned tuple requires a lot of memory, that can lead to
problems.
Instead change things so that the expression context can be reset once
per output tuple, which requires a new memory context to store SRF
arguments in.
This is a longstanding issue, but was hard to fix before 9.6, due to
the way tSRFs where evaluated. But it's fairly easy to fix now. We
could backpatch this into 10, but given there've been fewc omplaints
that doesn't seem worth the risk so far.
Reported-By: Lucas Fairchild
Author: Andres Freund, per discussion with Tom Lane
Discussion: https://postgr.es/m/4514.1507318623@sss.pgh.pa.us
copy_file() reads and writes data 64KB at a time (with default BLCKSZ),
and historically has issued a pg_flush_data request after each write.
This turns out to interact really badly with macOS's new APFS file
system: a large file copy takes over 100X longer than it ought to on
APFS, as reported by Brent Dearth. While that's arguably a macOS bug,
it's not clear whether Apple will do anything about it in the near
future, and in any case experimentation suggests that issuing flushes
a bit less often can be helpful on other platforms too.
Hence, rearrange the logic in copy_file() so that flush requests are
issued once per N writes rather than every time through the loop.
I set the FLUSH_DISTANCE to 32MB on macOS (any less than that still
results in a noticeable speed degradation on APFS), but 1MB elsewhere.
In limited testing on Linux and FreeBSD, this seems slightly faster
than the previous code, and certainly no worse. It helps noticeably
on macOS even with the older HFS filesystem.
A simpler change would have been to just increase the size of the
copy buffer without changing the loop logic, but that seems likely
to trash the processor cache without really helping much.
Back-patch to 9.6 where we introduced msync() as an implementation
option for pg_flush_data(). The problem seems specific to APFS's
mmap/msync support, so I don't think we need to go further back.
Discussion: https://postgr.es/m/CADkxhTNv-j2jw2g8H57deMeAbfRgYBoLmVuXkC=YCFBXRuCOww@mail.gmail.com
If the operator is a strict btree equality operator, and X isn't volatile,
then the clause must yield true for any non-null value of X, or null if X
is null. At top level of a WHERE clause, we can ignore the distinction
between false and null results, so it's valid to simplify the clause to
"X IS NOT NULL". This is a useful improvement mainly because we'll get
a far better selectivity estimate in most cases.
Because such cases seldom arise in well-written queries, it is unappetizing
to expend a lot of planner cycles looking for them ... but it turns out
that there's a place we can shoehorn this in practically for free, because
equivclass.c already has to detect and reject candidate equivalences of the
form X = X. That doesn't catch every place that it would be valid to
simplify to X IS NOT NULL, but it catches the typical case. Working harder
doesn't seem justified.
Patch by me, reviewed by Petr Jelinek
Discussion: https://postgr.es/m/CAMjNa7cC4X9YR-vAJS-jSYCajhRDvJQnN7m2sLH1wLh-_Z2bsw@mail.gmail.com
The previous coding here trashed the line buffer as it scanned it,
making it impossible to print the source line in subsequent error
messages. With a few save/restore/strdup pushups we can improve
that situation.
In passing, move the free'ing of the various strings that are collected
while processing one set of tests down to the bottom of the loop.
That's simpler, less surprising, and should make valgrind less unhappy
about the strings that were previously leaked by the last iteration.
Peter Eisentraut
Tom Lane
Joe Conway
Andres Freund
Robert Haas
Alvaro Herrera