For DocBook XML compatibility, don't use SGML empty tags (</>) anymore,
replace by the full tag name.  Add a warning option to catch future
occurrences.

Alexander Lakhin, Jürgen Purtz

Reported by: David G. Johnston
Discussion: https://postgr.es/m/CAKFQuwajWqjqEL9xc1xnnmTyBg32EdAZKJXijzigbosGSs_vag@mail.gmail.com

setTargetTable threw an error if the proposed target RangeVar's relname
matched any visible CTE or ENR.  This breaks backwards compatibility in
the CTE case, since pre-v10 we never looked for a CTE here at all, so that
CTE names did not mask regular tables.  It does seem like a good idea to
throw an error for the ENR case, though, thus causing ENRs to mask tables
for this purpose; ENRs are new in v10 so we're not breaking existing code,
and we may someday want to allow them to be the targets of DML.

To fix that, replace use of getRTEForSpecialRelationTypes, which was
overkill anyway, with use of scanNameSpaceForENR.

A second problem was that the check neglected to verify null schemaname,
so that a CTE or ENR could incorrectly be thought to match a qualified
RangeVar.  That happened because getRTEForSpecialRelationTypes relied
on its caller to have checked for null schemaname.  Even though the one
remaining caller got it right, this is obviously bug-prone, so move
the check inside getRTEForSpecialRelationTypes.

Also, revert commit 18ce3a4a's extremely poorly thought out decision to
add a NULL return case to parserOpenTable --- without either documenting
that or adjusting any of the callers to check for it.  The current bug
seems to have arisen in part due to working around that bad idea.

In passing, remove the one-line shim functions transformCTEReference and
transformENRReference --- they don't seem to be adding any clarity or
functionality.

Per report from Hugo Mercier (via Julien Rouhaud).  Back-patch to v10
where the bug was introduced.

Thomas Munro, with minor editing by me

Discussion: https://postgr.es/m/CAOBaU_YdPVH+PTtiKSSLOiiW3mVDYsnNUekK+XPbHXiP=wrFLA@mail.gmail.com

Flex generates a lot of functions that are not actually used.  In order
to avoid coverage figures being ruined by that, mark up the part of the
.l files where the generated code appears by lcov exclusion markers.
That way, lcov will typically only reported on coverage for the .l file,
which is under our control, but not for the .c file.
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>

There is no reason to insist that direct arguments must match before
we can merge transition states of two aggregate calls.  They're only
used during the finalfn call, so we can treat them as like the finalfn
itself.  This allows, eg, merging of

select
  percentile_cont(0.25) within group (order by a),
  percentile_disc(0.5) within group (order by a)
from ...

This didn't matter (and could not have been tested) before we allowed
state merging of OSAs otherwise.

Discussion: https://postgr.es/m/CAB4ELO5RZhOamuT9Xsf72ozbenDLLXZKSk07FiSVsuJNZB861A@mail.gmail.com

The built-in OSAs all share the same transition function, so they can
share transition state as long as the final functions cooperate to not
do the sort step more than once.  To avoid running the tuplesort object
in randomAccess mode unnecessarily, add a bit of infrastructure to
nodeAgg.c to let the aggregate functions find out whether the transition
state is actually being shared or not.

This doesn't work for the hypothetical aggregates, since those inject
a hypothetical row that isn't traceable to the shared input state.
So they remain marked aggfinalmodify = 'w'.

Discussion: https://postgr.es/m/CAB4ELO5RZhOamuT9Xsf72ozbenDLLXZKSk07FiSVsuJNZB861A@mail.gmail.com

An aggregate's input expression(s) are not supposed to be evaluated
at all for a row where its FILTER test fails ... but commit 8ed3f11b
overlooked that requirement.  Reshuffle so that aggregates having a
filter clause evaluate their arguments separately from those without.
This still gets the benefit of doing only one ExecProject in the
common case of multiple Aggrefs, none of which have filters.

While at it, arrange for filter clauses to be included in the common
ExecProject evaluation, thus perhaps buying a little bit even when
there are filters.

Back-patch to v10 where the bug was introduced.

Discussion: https://postgr.es/m/30065.1508161354@sss.pgh.pa.us

Simplify coding using a switch rather than nested if tests.

Author: Álvaro
Reviewed-by: Robert Haas, Amit Langote, Michaël Paquier
Discussion: https://postgr.es/m/20171013163820.pai7djcaxrntaxtn@alvherre.pgsql

While poking around in the aggregate logic, I noticed that commit
8ed3f11b broke the logic in nodeAgg.c that purports to detect nested
aggregates, by moving initialization of regular aggregate argument
expressions out of the code segment that checks for that.

You could argue that this check is unnecessary, but it's not much code
so I'm inclined to keep it as a backstop against parser and planner
bugs.  However, there's certainly zero value in checking only some of
the subexpressions.

We can make the check complete again, and as a bonus make it a good
deal more bulletproof against future mistakes of the same ilk, by
moving it out to the outermost level of ExecInitAgg.  This means we
need to check only once per Agg node not once per aggregate, which
also seems like a good thing --- if the check does find something
wrong, it's not urgent that we report it before the plan node
initialization finishes.

Since this requires remembering the original length of the aggs list,
I deleted a long-obsolete stanza that changed numaggs from 0 to 1.
That's so old it predates our decision that palloc(0) is a valid
operation, in (digs...) 2004, see commit 24a1e20f.

In passing improve a few comments.

Back-patch to v10, just in case.

Buildfarm member gaur says it wasn't there in 2.95.3.  Guess that 3.0
and later have it.

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 804163bc 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 c3d9a660, 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
1c497fa7.  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 4c119fbc 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

Apparently, an older spelling of LDAP_OPT_DIAGNOSTIC_MESSAGE is
LDAP_OPT_ERROR_STRING, so fall back to that one.

Diagnostic messages seem likely to help users diagnose root
causes more easily, so let's report them as errdetail.

Author: Thomas Munro
Reviewed-By: Ashutosh Bapat, Christoph Berg, Alvaro Herrera, Peter Eisentraut
Discussion: https://postgr.es/m/CAEepm=2_dA-SYpFdmNVwvKsEBXOUj=K4ooKovHmvj6jnMdt8dw@mail.gmail.com

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 36b4b91b.

Author: Andres Freund
Discussion: https://postgr.es/m/2656.1507830907@sss.pgh.pa.us

Marginal efficiency and beautification hack.  I'm not sure whether
this case ever arises currently, but the pending patch for update
tuple routing will cause it to arise.

Amit Khandekar

Discussion: http://postgr.es/m/CAJ3gD9cazfppe7-wwUbabPcQ4_0SubkiPFD1+0r5_DkVNWo5yg@mail.gmail.com

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 804163bc 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

Commits 6476b261
and 14f67a8e didn't use quite the
same error message for what is basically the same situation.

Amit Langote, pared back a bit by me.

Discussion: http://postgr.es/m/54dc76d0-3b5b-ba5a-27dc-fb31a3975b61@lab.ntt.co.jp

Ioseph Kim

Discussion: https://postgr.es/m/e7a79f91-8244-5bcb-afcc-96c817e86f4e@postgresql.kr

Vars hidden within a RelabelType would not be detected as compatible
with some functional dependency.  Repair by properly ignoring the
RelabelType.

Author: David Rowley
Reviewed-by: Tomas Vondra
Discussion: https://postgr.es/m/CAKJS1f-y-UEy=rsBXynBOgiW1fKMr_LVoYSGL9QOc36mLEC-ww@mail.gmail.com

Before, that would fail to happen unless a BEFORE ROW UPDATE trigger
was also present.

Noted by me while reviewing a patch from Masahiko Sawada, who also
wrote this patch.  Reviewed by Petr Jelinek.

Discussion: http://postgr.es/m/CA+TgmobAZvCxduG8y_mQKBK7nz-vhbdLvjM354KEFozpuzMN5A@mail.gmail.com

pq_sendint() remains, so extension code doesn't unnecessarily break.

Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de

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 804163bc 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
81c5e46c 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