If a sub-select's output column is a simple Var, recursively look for
statistics applying to that Var, and use them if available.  The need for
this was foreseen ages ago, but we didn't have enough infrastructure to do
it with reasonable speed until just now.

We punt and stick with default estimates if the subquery uses set
operations, GROUP BY, or DISTINCT, since those operations would change the
underlying column statistics (particularly, the relative frequencies of
different values) beyond recognition.  This means that the types of
sub-selects for which this improvement applies are fairly limited, since
most subqueries satisfying those restrictions would have gotten flattened
into the parent query anyway.  But it does help for some cases, such as
subqueries with ORDER BY or LIMIT.

Since the subroots will surely link back to the same glob struct, this
necessarily leads to infinite recursion.  Doh.  Found while trying to
debug some other code.

walsender.h should depend on xlog.h, not vice versa.  (Actually, the
inclusion was circular until a couple hours ago, which was even sillier;
but Bruce broke it in the expedient rather than logically correct
direction.)  Because of that poor decision, plus blind application of
pgrminclude, we had a situation where half the system was depending on
xlog.h to include such unrelated stuff as array.h and guc.h.  Clean up
the header inclusion, and manually revert a lot of what pgrminclude had
done so things build again.

This episode reinforces my feeling that pgrminclude should not be run
without adult supervision.  Inclusion changes in header files in particular
need to be reviewed with great care.  More generally, it'd be good if we
had a clearer notion of module layering to dictate which headers can sanely
include which others ... but that's a big task for another day.

storage/proc.h should not include replication/syncrep.h, especially not
when the latter includes storage/proc.h; but in any case this was a pretty
poor thing from a modular layering standpoint.

file.

Per suggestion from Alvaro.

Per suggestion from Peter.

">" should be ">>".  This typo results in failure to use all of the bits
of the provided seed.

This might rise to the level of a security bug if we were relying on
srand48 for any security-critical purposes, but we are not --- in fact,
it's not used at all unless the platform lacks srandom(), which is
improbable.  Even on such a platform the exposure seems minimal.

Reported privately by Andres Freund.

Formerly, set_subquery_pathlist and other creators of plans for subqueries
saved only the rangetable and rowMarks lists from the lower-level
PlannerInfo.  But there's no reason not to remember the whole PlannerInfo,
and indeed this turns out to simplify matters in a number of places.

The immediate reason for doing this was so that the subroot will still be
accessible when we're trying to extract column statistics out of an
already-planned subquery.  But now that I've done it, it seems like a good
code-beautification effort in its own right.

I also chose to get rid of the transient subrtable and subrowmark fields in
SubqueryScan nodes, in favor of having setrefs.c look up the subquery's
RelOptInfo.  That required changing all the APIs in setrefs.c to pass
PlannerInfo not PlannerGlobal, which was a large but quite mechanical
transformation.

One side-effect not foreseen at the beginning is that this finally broke
inheritance_planner's assumption that replanning the same subquery RTE N
times would necessarily give interchangeable results each time.  That
assumption was always pretty risky, but now we really have to make a
separate RTE for each instance so that there's a place to carry the
separate subroots.

In the past, relhassubclass always remained true if a relation had ever had
child relations, even if the last subclass was long gone.  While this had
only marginal performance implications in most cases, it was annoying, and
I'm now considering some planner changes that would raise the cost of a
false positive.  It was previously impractical to fix this because of race
condition concerns.  However, given the recent change that made tablecmds.c
take ShareExclusiveLock on relations that are gaining a child (commit
fbcf4b92), we can now allow ANALYZE to
clear the flag when it's no longer relevant.  There is no additional
locking cost to do so, since ANALYZE takes ShareExclusiveLock anyway.

Fix pgrminclude C comment marker.

changes for the win32 setlocale() wrapper I put into ecpg, to make it compile
on MinGW.

1. Use new dropdb --if-exists option, to avoid alarming the user if
   the database being dropped doesn't already exist.
2. Bail out if createdb fails.
3. exit 1 if the checks fail.
4. Make it executable.

Josh Kupershmidt, with some kibitzing by me.

KaiGai Kohei

Don't test whether the number of labels is numerically equal to zero;
count(*) isn't going return zero anyway, and the current coding blows
up if it returns an empty string or an error.

builfarm member.

on Windows. ecpglib doesn't link with libpgport, but picks and compiles
the .c files it needs individually. To cope with that, move the setlocale()
wrapper from chklocale.c to a separate setlocale.c file, and include that
in ecpglib.

dots. I previously worked around this in initdb, mapping the known
problematic locale names to aliases that work, but Hiroshi Inoue pointed
out that that's not enough because even if you use one of the aliases, like
"Chinese_HKG", setlocale(LC_CTYPE, NULL) returns back the long form, ie.
"Chinese_Hong Kong S.A.R.". When we try to restore an old locale value by
passing that value back to setlocale(), it fails. Note that you are affected
by this bug also if you use one of those short-form names manually, so just
reverting the hack in initdb won't fix it.

To work around that, move the locale name mapping from initdb to a wrapper
around setlocale(), so that the mapping is invoked on every setlocale() call.

Also, add a few checks for failed setlocale() calls in the backend. These
calls shouldn't fail, and if they do there isn't much we can do about it,
but at least you'll get a warning.

Backpatch to 9.1, where the initdb hack was introduced. The Windows bug
affects older versions too if you set locale manually to one of the aliases,
but given the lack of complaints from the field, I'm hesitent to backpatch.

ifdef block. It has nothing to do with whether the replacement snprintf
function is used. It caused no live bug, because the replacement snprintf
function is always used on Win32, but it was nevertheless misplaced.

Examination of examples provided by Mark Kirkwood and others has convinced
me that actually commit 7f3eba30 was quite
a few bricks shy of a load.  The useful part of that patch was clamping
ndistinct for the inner side of a semi or anti join, and the reason why
that's needed is that it's the only way that restriction clauses
eliminating rows from the inner relation can affect the estimated size of
the join result.  I had not clearly understood why the clamping was
appropriate, and so mis-extrapolated to conclude that we should clamp
ndistinct for the outer side too, as well as for both sides of regular
joins.  These latter actions were all wrong, and are reverted with this
patch.  In addition, the clamping logic is now made to affect the behavior
of both paths in eqjoinsel_semi, with or without MCV lists to compare.
When we have MCVs, we suppose that the most common values are the ones
that are most likely to survive the decimation resulting from a lower
restriction clause, so we think of the clamping as eliminating non-MCV
values, or potentially even the least-common MCVs for the inner relation.

Back-patch to 8.4, same as previous fixes in this area.

This fixes a pg_upgrade bug that could lead to query errors when
clog files are improperly removed.

Backpatch to 8.4, 9.0, 9.1.

This patch fixes an oversight in my commit
7f3eba30 of 2008-10-23.  That patch
accounted for baserel restriction clauses that reduced the number of rows
coming out of a table (and hence the number of possibly-distinct values of
a join variable), but not for join restriction clauses that might have been
applied at a lower level of join.  To account for the latter, look up the
sizes of the min_lefthand and min_righthand inputs of the current join,
and clamp with those in the same way as for the base relations.

Noted while investigating a complaint from Ben Chobot, although this in
itself doesn't seem to explain his report.

Back-patch to 8.4; previous versions used different estimation methods
for which this heuristic isn't relevant.

lowercase earlier, but documentation was not updated. Update the docs.

Fujii Masao

There's no reason for this test to use the undocumented pg_prepared_xact()
function, when it can use the stable API pg_prepared_xacts instead.
Fixes breakage against 8.3, as reported by Justin Arnold.

It is possible for VACUUM to scan no pages at all, if the visibility map
shows that all pages are all-visible.  In this situation VACUUM has no new
information to report about the relation's tuple density, so it wasn't
changing pg_class.reltuples ... but it updated pg_class.relpages anyway.
That's wrong in general, since there is no evidence to justify changing the
density ratio reltuples/relpages, but it's particularly bad if the previous
state was relpages=reltuples=0, which means "unknown tuple density".
We just replaced "unknown" with "zero".  ANALYZE would eventually recover
from this, but it could take a lot of repetitions of ANALYZE to do so if
the relation size is much larger than the maximum number of pages ANALYZE
will scan, because of the moving-average behavior introduced by commit
b4b6923e.

The only known situation where we could have relpages=reltuples=0 and yet
the visibility map asserts everything's visible is immediately following
a pg_upgrade.  It might be advisable for pg_upgrade to try to preserve the
relpages/reltuples statistics; but in any case this code is wrong on its
own terms, so fix it.  Per report from Sergey Koposov.

Back-patch to 8.4, where the visibility map was introduced, same as the
previous change.

Put options listing in a less random order, fix capitalization, and
some typos.

Josh Kupershmidt

Josh Kupershmidt, with some further editing by me.