This patch adjusts the treatment of parameterized paths so that all paths
with the same parameterization (same set of required outer rels) for the
same relation will have the same rowcount estimate.  We cache the rowcount
estimates to ensure that property, and hopefully save a few cycles too.
Doing this makes it practical for add_path_precheck to operate without
a rowcount estimate: it need only assume that paths with different
parameterizations never dominate each other, which is close enough to
true anyway for coarse filtering, because normally a more-parameterized
path should yield fewer rows thanks to having more join clauses to apply.

In add_path, we do the full nine yards of comparing rowcount estimates
along with everything else, so that we can discard parameterized paths that
don't actually have an advantage.  This fixes some issues I'd found with
add_path rejecting parameterized paths on the grounds that they were more
expensive than not-parameterized ones, even though they yielded many fewer
rows and hence would be cheaper once subsequent joining was considered.

To make the same-rowcounts assumption valid, we have to require that any
parameterized path enforce *all* join clauses that could be obtained from
the particular set of outer rels, even if not all of them are useful for
indexing.  This is required at both base scans and joins.  It's a good
thing anyway since the net impact is that join quals are checked at the
lowest practical level in the join tree.  Hence, discard the original
rather ad-hoc mechanism for choosing parameterization joinquals, and build
a better one that has a more principled rule for when clauses can be moved.
The original rule was actually buggy anyway for lack of knowledge about
which relations are part of an outer join's outer side; getting this right
requires adding an outer_relids field to RestrictInfo.

Like with SGML files, using tabs in these files is confusing and
unnecessary.

This has been wrong for a really long time.  We don't use two-phase
locking to protect against serialization anomalies.

Per discussion on pgsql-hackers about 2011-03-07; original report
by Dan Ports.

Commit 8e5ac74c tried to do this renaming,
but I relied on gcc to tell me where I needed to make changes, instead of
grep.

Noted by Jeff Davis.

The previous code could cause a backend crash after BEGIN; SAVEPOINT a;
LOCK TABLE foo (interrupted by ^C or statement timeout); ROLLBACK TO
SAVEPOINT a; LOCK TABLE foo, and might have leaked strong-lock counts
in other situations.

Report by Zoltán Böszörményi; patch review by Jeff Davis.

Noah Misch spotted the fact that the old comment is in fact incorrect, due
to memory ordering hazards.

Previously, we used SetBufferCommitInfoNeedsSave, but that's really
intended for dirty-marks we can theoretically afford to lose, such as
hint bits.  As for 9.2, the PD_ALL_VISIBLE mustn't be lost in this
way, since we could then end up with a heap page that isn't
all-visible and a visibility map page that is all visible, causing
index-only scans to return wrong answers.

Noah Misch

Mostly, this consists of adding support for fields which exist in the
structure but aren't handled by copy/equal/outfuncs; but the create
foreign table case can actually produce garbage output.

Noah Misch

Fujii Masao

Previously, the use of the optional key word WITH was not supported.

Josh Kupershmidt

A number of utility programs were rather careless about paremeters
that can be set via both an option argument and a positional
argument. This leads to results which can violate the Principal
Of Least Astonishment. These changes refuse to use positional
arguments to override settings that have been made via positional
arguments. The changes are backpatched to all live branches.

When using synchronous replication, we waited for the commit record to be
replicated, but if we our transaction didn't write any other WAL records,
that's not required because we don't even flush the WAL locally to disk in
that case. This lead to long waits when committing a transaction that only
modified a temporary table. Bug spotted by Thom Brown.

Kyotaro HORIGUCHI

The header file is needed by any module that wants to use the PL/pgSQL
instrumentation plugin interface. Most notably, the pldebugger plugin needs
this. With this patch, it can be built using pgxs, without having the full
server source tree available.

Clarify that nrows() is the number of rows processed, versus the
number of rows returned, which can be obtained using len.  Also add
tests about that.

The result object methods colnames() etc. would crash when called
after a command that did not produce a result set.  Now they throw an
exception.

discovery and initial patch by Jean-Baptiste Quenot

message. They are already implemented in the source code.
Suggestions about the message formatting from Tom Lane.

Fujii Masao, per discussion on pgsql-hackers

The output of the new pg_xlog_location_diff function is of type numeric,
since it could theoretically overflow an int8 due to signedness; this
provides a convenient way to format such values.

Fujii Masao, with some beautification by me.

discussion of hackers list on 2012/3/10 "missing description initdb
manual".

Remove lots of outdated information that is duplicated by the
better-maintained SGML documentation.  In particular, remove the
outdated listing of contrib modules.  Update the installation
instructions to mention CREATE EXTENSION, but don't go into too much
detail.

Etsuro Fujita

So far as I can tell, it is no longer possible for this heuristic to do
anything useful, because the new weaker definition of
have_relevant_joinclause means that any relation with a joinclause must be
considered joinable to at least one other relation.  It would still be
possible for the code block to be entered, for example if there are join
order restrictions that prevent any join of the current level from being
formed; but in that case it's just a waste of cycles to attempt to form
cartesian joins, since the restrictions will still apply.

Furthermore, IMO the existence of this code path can mask bugs elsewhere;
we would have noticed the problem with cartesian joins a lot sooner if
this code hadn't compensated for it in the simplest case.

Accordingly, let's remove it and see what happens.  I'm committing this
separately from the prerequisite changes in have_relevant_joinclause,
just to make the question easier to revisit if there is some fault in
my logic.

We should be willing to cross-join two small relations if that allows us
to use an inner indexscan on a large relation (that is, the potential
indexqual for the large table requires both smaller relations).  This
worked in simple cases but fell apart as soon as there was a join clause
to a fourth relation, because the existence of any two-relation join clause
caused the planner to not consider clauseless joins between other base
relations.  The added regression test shows an example case adapted from
a recent complaint from Benoit Delbosc.

Adjust have_relevant_joinclause, have_relevant_eclass_joinclause, and
has_relevant_eclass_joinclause to consider that a join clause mentioning
three or more relations is sufficient grounds for joining any subset of
those relations, even if we have to do so via a cartesian join.  Since such
clauses are relatively uncommon, this shouldn't affect planning speed on
typical queries; in fact it should help a bit, because the latter two
functions in particular get significantly simpler.

Although this is arguably a bug fix, I'm not going to risk back-patching
it, since it might have currently-unforeseen consequences.

Per mailing list discussion, we would like to keep the bytea functions
parallel to the text functions, so rename bytea_agg to string_agg,
which already exists for text.

Also, to satisfy the rule that we don't want aggregate functions of
the same name with a different number of arguments, add a delimiter
argument, just like string_agg for text already has.

Christoph Berg

The previous comment described how things worked in PostgreSQL 8.2
and prior.

Thom Brown

cost_index's method for estimating per-tuple costs of evaluating filter
conditions (a/k/a qpquals) was completely wrong in the presence of derived
indexable conditions, such as range conditions derived from a LIKE clause.
This was largely masked in common cases as a result of all simple operator
clauses having about the same costs, but it could show up in a big way when
dealing with functional indexes containing expensive functions, as seen for
example in bug #6579 from Istvan Endredy.  Rejigger the calculation to give
sane answers when the indexquals aren't a subset of the baserestrictinfo
list.  As a side benefit, we now do the calculation properly for cases
involving join clauses (ie, parameterized indexscans), which we always
overestimated before.

There are still cases where this is an oversimplification, such as clauses
that can be dropped because they are implied by a partial index's
predicate.  But we've never accounted for that in cost estimates before,
and I'm not convinced it's worth the cycles to try to do so.

Previously we attempted to throw an error or at least warning for missing
schemas, but this was done inconsistently because of implementation
restrictions (in many cases, GUC settings are applied outside transactions
so that we can't do system catalog lookups).  Furthermore, there were
exceptions to the rule even in the beginning, and we'd been poking more
and more holes in it as time went on, because it turns out that there are
lots of use-cases for having some irrelevant items in a common search_path
value.  It seems better to just adopt a philosophy similar to what's always
been done with Unix PATH settings, wherein nonexistent or unreadable
directories are silently ignored.

This commit also fixes the documentation to point out that schemas for
which the user lacks USAGE privilege are silently ignored.  That's always
been true but was previously not documented.

This is mostly in response to Robert Haas' complaint that 9.1 started to
throw errors or warnings for missing schemas in cases where prior releases
had not.  We won't adopt such a significant behavioral change in a back
branch, so something different will be needed in 9.1.

postgres:// URIs are an attempt to "stop the bleeding" in this general
area that has been said to occur due to external projects adopting their
own syntaxes.  The syntaxes supported by this patch:

 postgres://[user[:pwd]@][unix-socket][:port[/dbname]][?param1=value1&...]
 postgres://[user[:pwd]@][net-location][:port][/dbname][?param1=value1&...]

should be enough to cover most interesting cases without having to
resort to "param=value" pairs, but those are provided for the cases that
need them regardless.

libpq documentation has been shuffled around a bit, to avoid stuffing
all the format details into the PQconnectdbParams description, which was
already a bit overwhelming.  The list of keywords has moved to its own
subsection, and the details on the URI format live in another subsection.

This includes a simple test program, as requested in discussion, to
ensure that interesting corner cases continue to work appropriately in
the future.

Author: Alexander Shulgin
Some tweaking by Álvaro Herrera, Greg Smith, Daniel Farina, Peter Eisentraut
Reviewed by Robert Haas, Alexey Klyukin (offlist), Heikki Linnakangas,
Marko Kreen, and others

Oh, it also supports postgresql:// but that's probably just an accident.

This definition is convenient when applying the function to the
reltablespace column of pg_class, since that's what zero means there;
and it doesn't interfere with any other plausible use of the function.
Per gripe from Bruce Momjian.

default tablespace, but part of a database that is in a user-defined
tablespace.  Caused "file not found" error during upgrade.

Per bug report from Ants Aasma.

Backpatch to 9.1 and 9.0.

Since xgettext provides options to do this now, we might as well use
them.