By building it unconditionally, libpgport inadvertently replaced any
libc version of the function.  This is essentially a code cleanup; any
effect on performance is almost surely too small to notice.

Though the one contemporary caller uses it in a limited way, this
function could loop indefinitely if pointed to an arbitrary PID.

This role attribute is an ancient PostgreSQL feature, but could only be
set by directly updating the system catalogs, and it doesn't have any
clearly defined use.

Author: Adam Brightwell <adam.brightwell@crunchydatasolutions.com>

Fabien Coelho
Reviewed by Robert Haas

Commit 7b583b20 created an unnecessary
dump failure hazard by applying pg_get_function_identity_arguments()
to every function in the database, even those that won't get dumped.
This could result in snapshot-related problems if concurrent sessions are,
for example, creating and dropping temporary functions, as noted by Marko
Tiikkaja in bug #12832.  While this is by no means pg_dump's only such
issue with concurrent DDL, it's unfortunate that we added a new failure
mode for cases that used to work, and even more so that the failure was
created for basically cosmetic reasons (ie, to sort overloaded functions
more deterministically).

To fix, revert that patch and instead sort function arguments using
information that pg_dump has available anyway, namely the names of the
argument types.  This will produce a slightly different sort ordering for
overloaded functions than the previous coding; but applying strcmp
directly to the output of pg_get_function_identity_arguments really was
a bit odd anyway.  The sorting will still be name-based and hence
independent of possibly-installation-specific OID assignments.  A small
additional benefit is that sorting now works regardless of server version.

Back-patch to 9.3, where the previous commit appeared.

I forgot to update it on yesterday's cf34e373.

We were using "user mapping for user XYZ" as description for user mappings, but
that's ambiguous because users can have mappings on multiple foreign
servers; therefore change it to "for user XYZ on server UVW" instead.
Object identities for user mappings are also updated in the same way, in
branches 9.3 and above.

The incomplete description string was introduced together with the whole
SQL/MED infrastructure by commit cae565e5 of 8.4 era, so backpatch all
the way back.

An OID return value was being used only for a (rather pointless) assert.
Silence by removing the variable and the assert.

Per note from Peter Geoghegan

This hasn't been true in quite some time, cf plpgsql's make_datum_param().

Oversight in my commit b9896198.

I had thought that there was no need to maintain separate cache entries
for different source typmods, but further experimentation shows that there
is an advantage to doing so in some cases.  In particular, if a domain has
a typmod (say, "CREATE DOMAIN d AS numeric(20,0)"), failing to notice the
source typmod leads to applying a length-coercion step even when the
source has the correct typmod.

This is because can_coerce_type thinks that RECORD can be cast to any
composite type, but coerce_record_to_complex only works for inputs that are
RowExprs or whole-row Vars, so we get a hard failure on a CaseTestExpr.

Perhaps these corner cases ought to be fixed so that coerce_to_target_type
actually returns NULL as per its specification, rather than failing ...
but for the moment an extra check here is the path of least resistance.

plpgsql's historical method for converting datatypes during assignments was
to apply the source type's output function and then the destination type's
input function.  Aside from being miserably inefficient in most cases, this
method failed outright in many cases where a user might expect it to work;
an example is that "declare x int; ... x := 3.9;" would fail, not round the
value to 4.

Instead, let's convert by applying the appropriate assignment cast whenever
there is one.  To avoid breaking compatibility unnecessarily, fall back to
the I/O conversion method if there is no assignment cast.

So far as I can tell, there is just one case where this method produces a
different result than the old code in a case where the old code would not
have thrown an error.  That is assignment of a boolean value to a string
variable (type text, varchar, or bpchar); the old way gave boolean's output
representation, ie 't'/'f', while the new way follows the behavior of the
bool-to-text cast and so gives 'true' or 'false'.  This will need to be
called out as an incompatibility in the 9.5 release notes.

Aside from handling many conversion cases more sanely, this method is
often significantly faster than the old way.  In part that's because
of more effective caching of the conversion info.

genericcostestimate() and friends used the cost of the entire indexqual
expressions as the charge for initial evaluation of indexscan arguments.
But of course the index column is not evaluated, only the other side
of the qual expression, so this was a bad overestimate if the index
column was an expensive expression.

To fix, refactor the logic in this area so that there's a single routine
charged with deconstructing index quals and figuring out what is the index
column and what is the comparison expression.  This is more or less free in
the case of btree indexes, since btcostestimate() was doing equivalent
deconstruction already.  It probably adds a bit of new overhead in the cases
of other index types, but not a lot.  (In the case of GIN I think I saved
something by getting rid of code that wasn't aware that the index column
associations were already available "for free".)

Per recent gripe from Jeff Janes.

Arguably this is a bug fix, but I'm hesitant to back-patch because of the
possibility of destabilizing plan choices that people may be happy with.

Peter Geoghegan

This code relied on pointer equality to identify which restriction clauses
also appear in the indexquals (and, therefore, don't need to be applied as
simple filter conditions).  That was okay once upon a time, years ago,
before we introduced the equivalence-class machinery.  Now there's about a
50-50 chance that an equality clause appearing in the indexquals will be
the mirror image (commutator) of its mate in the restriction list.  When
that happens, we'd erroneously think that the clause would be re-evaluated
at each visited row, and therefore inflate the cost estimate for the
indexscan by the clause's cost.

Add some logic to catch this case.  It seems to me that it continues not to
be worthwhile to expend the extra predicate-proof work that createplan.c
will do on the finally-selected plan, but this case is common enough and
cheap enough to handle that we should do so.

This will make a small difference (about one cpu_operator_cost per row)
in simple cases; but in situations where there's an expensive function in
the indexquals, it can make a very large difference, as seen in recent
example from Jeff Janes.

This is a long-standing bug, but I'm hesitant to back-patch because of the
possibility of destabilizing plan choices that people may be happy with.

Passing a NULL pstate wouldn't actually work, because isLockedRefname()
isn't prepared to cope with it; and there hasn't been any in-core code
that tries in over a decade.  So just remove the residual NULL handling.

Spotted by Coverity; analysis and patch by Michael Paquier.

The changed routines are mostly those that can be directly called by
ProcessUtilitySlow; the intention is to make the affected object
information more precise, in support for future event trigger changes.
Originally it was envisioned that the OID of the affected object would
be enough, and in most cases that is correct, but upon actually
implementing the event trigger changes it turned out that ObjectAddress
is more widely useful.

Additionally, some command execution routines grew an output argument
that's an object address which provides further info about the executed
command.  To wit:

* for ALTER DOMAIN / ADD CONSTRAINT, it corresponds to the address of
  the new constraint

* for ALTER OBJECT / SET SCHEMA, it corresponds to the address of the
  schema that originally contained the object.

* for ALTER EXTENSION {ADD, DROP} OBJECT, it corresponds to the address
  of the object added to or dropped from the extension.

There's no user-visible change in this commit, and no functional change
either.

Discussion: 20150218213255.GC6717@tamriel.snowman.net
Reviewed-By: Stephen Frost, Andres Freund

This was missed in my commit f4c4335a of 9.3 vintage, so backpatch to
that.

There's no reason to make users write an explicit cast to store a
json value in a jsonb column or vice versa.

We could probably even make these implicit, but that might open us up
to problems with ambiguous function calls, so for now just do this.

My commit 878fdcb8 was not quite
right.  Tom Lane pointed out one of the mistakes fixed here, and I
noticed the other myself while reviewing what I'd committed.

Evidently from commit 878fdcb8.
Per buildfarm.

Previously, you could do \set variable operand1 operator operand2, but
nothing more complicated.  Now, you can \set variable expression, which
makes it much simpler to do multi-step calculations here.  This also
adds support for the modulo operator (%), with the same semantics as in
C.

Robert Haas and Fabien Coelho, reviewed by Álvaro Herrera and
Stephen Frost

Since 9.1, we've provided extensions with a way to denote
"configuration" tables- tables created by an extension which the user
may modify.  By marking these as "configuration" tables, the extension
is asking for the data in these tables to be pg_dump'd (tables which
are not marked in this way are assumed to be entirely handled during
CREATE EXTENSION and are not included at all in a pg_dump).

Unfortunately, pg_dump neglected to consider foreign key relationships
between extension configuration tables and therefore could end up
trying to reload the data in an order which would cause FK violations.

This patch teaches pg_dump about these dependencies, so that the data
dumped out is done so in the best order possible.  Note that there's no
way to handle circular dependencies, but those have yet to be seen in
the wild.

The release notes for this should include a caution to users that
existing pg_dump-based backups may be invalid due to this issue.  The
data is all there, but restoring from it will require extracting the
data for the configuration tables and then loading them in the correct
order by hand.

Discussed initially back in bug #6738, more recently brought up by
Gilles Darold, who provided an initial patch which was further reworked
by Michael Paquier.  Further modifications and documentation updates
by me.

Back-patch to 9.1 where we added the concept of extension configuration
tables.

In 6f9bd50e, we modified
expand_security_quals() to tell expand_security_qual() about when the
current RTE was the targetRelation.  Unfortunately, that commit
initialized the targetRelation variable used outside of the loop over
the RTEs instead of at the start of it.

This patch moves the variable and the initialization of it into the
loop, where it should have been to begin with.

Pointed out by Dean Rasheed.

Back-patch to 9.4 as the original commit was.

Previously, we cached domain constraints for the life of a query, or
really for the life of the FmgrInfo struct that was used to invoke
domain_in() or domain_check().  But plpgsql (and probably other places)
are set up to cache such FmgrInfos for the whole lifespan of a session,
which meant they could be enforcing really stale sets of constraints.
On the other hand, searching pg_constraint once per query gets kind of
expensive too: testing says that as much as half the runtime of a
trivial query such as "SELECT 0::domaintype" went into that.

To fix this, delegate the responsibility for tracking a domain's
constraints to the typcache, which has the infrastructure needed to
detect syscache invalidation events that signal possible changes.
This not only removes unnecessary repeat reads of pg_constraint,
but ensures that we never apply stale constraint data: whatever we
use is the current data according to syscache rules.

Unfortunately, the current configuration of the system catalogs means
we have to flush cached domain-constraint data whenever either pg_type
or pg_constraint changes, which happens rather a lot (eg, creation or
deletion of a temp table will do it).  It might be worth rearranging
things to split pg_constraint into two catalogs, of which the domain
constraint one would probably be very low-traffic.  That's a job for
another patch though, and in any case this patch should improve matters
materially even with that handicap.

This patch makes use of the recently-added memory context reset callback
feature to manage the lifespan of domain constraint caches, so that we
don't risk deleting a cache that might be in the midst of evaluation.

Although this is a bug fix as well as a performance improvement, no
back-patch.  There haven't been many if any field complaints about
stale domain constraint checks, so it doesn't seem worth taking the
risk of modifying data structures as basic as MemoryContexts in back
branches.

This makes "ALTER TABLE tabname ALTER tscol TYPE ... USING tscol AT TIME
ZONE 'UTC'" skip rewriting the table when altering from "timestamp" to
"timestamptz" or vice versa.  While it would be nicer still to optimize
this in the absence of the USING clause given timezone==UTC, transform
functions must consult IMMUTABLE facts only.

When the library already exists in the build directory, "ar" preserves
members not named on its command line.  This mattered when, for example,
a "configure" rerun dropped a file from $(LIBOBJS).  libpgport carried
the obsolete member until "make clean".  Back-patch to 9.0 (all
supported versions).

Initial experience with this feature suggests that instances of
MemoryContextCallback are likely to propagate into some widely-used headers
over time.  As things stood, that would result in pulling memutils.h or
at least memnodes.h into common headers, which does not seem desirable.
Instead, let's decide that this feature is part of the "ordinary palloc
user" API rather than the "specialized context management" API, and as
such should be declared in palloc.h not memutils.h.

As evidenced by measles in buildfarm.  Pointed out by Tom.

The main value of this change is to avoid expensive I/O conversions when
assigning to a variable that has a typmod specification, if the value
to be assigned is already known to have the right typmod.  This is
particularly valuable for arrays with typmod specifications; formerly,
in an assignment to an array element the entire array would invariably
get put through double I/O conversion to check the typmod, to absolutely
no purpose since we'd already properly coerced the new element value.

Extracted from my "expanded arrays" patch; this seems worth committing
separately, whatever becomes of that patch, since it's really an
independent issue.

As long as we're changing the function signatures, take the opportunity
to rationalize the argument lists of exec_assign_value, exec_cast_value,
and exec_simple_cast_value; that is, put the arguments into a saner order,
and get rid of the bizarre choice to pass exec_assign_value's isNull flag
by reference.

Part of the intent of the parameterized-path mechanism was to handle
star-schema queries efficiently, but some overly-restrictive search
limiting logic added in commit e2fa76d8
prevented such cases from working as desired.  Fix that and add a
regression test about it.  Per gripe from Marc Cousin.

This is arguably a bug rather than a new feature, so back-patch to 9.2
where parameterized paths were introduced.

Add documentation about the new reset callback mechanism.

Also, at long last, recast the existing text so that it describes the
current context mechanisms as established fact rather than something
we're going to implement.  Shoulda done that in 2001 or so ...

The type variable must get set on first iteration of the while loop,
but there are reasonably modern gcc versions that don't realize that.
Initialize it with a dummy value.  This undoes a removal of initialization
in commit 654809e7.

That is, MemoryContextReset() now means what was formerly meant by
MemoryContextResetAndDeleteChildren(), and the latter is now just a macro
alias for the former.  If you really want the functionality that was
formerly provided by MemoryContextReset(), what you have to do is
MemoryContextResetChildren() plus MemoryContextResetOnly() (which is a
new API to reset *only* the named context and not touch its children).

The reason for this change is that near fifteen years of experience has
proven that there is noplace where old-style MemoryContextReset() is
actually what you want.  Making that the default behavior has led to lots
of context-leakage bugs, while we've not found anyplace where it's actually
necessary to keep the child contexts; at least the standard regression
tests do not reveal anyplace where this change breaks anything.  And there
are upcoming patches that will introduce additional reasons why child
contexts need to be removed.

We could change existing calls of MemoryContextResetAndDeleteChildren to be
just MemoryContextReset, but for the moment I'll leave them alone; they're
not costing anything.

The way that columns are added to a view is by calling
AlterTableInternal with special subtype AT_AddColumnToView; but that
subtype is changed to AT_AddColumnRecurse by ATPrepAddColumn.  This has
no visible effect in the current code, since views cannot have
inheritance children (thus the recursion step is a no-op) and adding a
column to a view is executed identically to doing it to a table; but it
does make a difference for future event trigger code keeping track of
commands, because the current situation leads to confusing the case with
a normal ALTER TABLE ADD COLUMN.

Fix the problem by passing a flag to ATPrepAddColumn to prevent it from
changing the command subtype.  The event trigger code can then properly
ignore the subcommand.  (We could remove the call to ATPrepAddColumn,
since views are never typed, and there is never a need for recursion,
which are the two conditions that are checked by ATPrepAddColumn; but it
seems more future-proof to keep the call in place.)

This allows cleanup actions to be registered to be called just before a
particular memory context's contents are flushed (either by deletion or
MemoryContextReset).  The patch in itself has no use-cases for this, but
several likely reasons for wanting this exist.

In passing, per discussion, rearrange some boolean fields in struct
MemoryContextData so as to avoid wasted padding space.  For safety,
this requires making allowInCritSection's existence unconditional;
but I think that's a better approach than what was there anyway.

Typo "aggreagate" appeared three times, and the return value of function
JsonbIteratorNext() was being assigned to an int variable in a bunch of
places.

When a composite type being used in a typed table is modified by way
of ALTER TYPE, a table rewrite occurs appearing to come from ALTER TYPE.
The existing event_trigger.c code was unable to cope with that
and raised a spurious error.  The fix is just to accept that command
tag for the event, and document this properly.

Noted while fooling with deparsing of DDL commands.  This appears to be
an oversight in commit 618c9430.

Thanks to Mark Wong for documentation wording help.