PostgreSQL Weekly News – April 17 2011

== PostgreSQL Weekly News – April 17 2011 ==

PostgreSQL update releases 9.0.4, 8.4.8, 8.3.15, and 8.2.21 will be
out soon. Get ready to upgrade!

== PostgreSQL Product News ==

tail_n_mail 1.18.1, a Postgres log watcher program, released:

Bucardo 4.4.3, a Postgres multi-master replication system, released:

== PostgreSQL Jobs for April ==

== PostgreSQL Local ==

PostgreSQL Turkey User Group is organizing a one-day event at April
30, 2011. Follow @PgDayTR for details in Turkish.

Open Database Camp will be on May 7-9, 2011 in Sardinia, Italy

PGCon will be May 19-20, 2011 at the University of Ottawa, preceded by
two days of tutorials on May 17-18.

PG Session 2, on PostGIS, will be held on June 23rd in Paris. The CfP
is open!

pgbr will be in Sao Paulo, Brazil November 3-4, 2011.

== PostgreSQL in the News ==

Planet PostgreSQL:

PostgreSQL Weekly News is brought to you this week by David Fetter

Submit news and announcements by Sunday at 3:00pm Pacific time.
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== Reviews ==

== Applied Patches ==

Heikki Linnakangas pushed:

– TransferPredicateLocksToNewTarget should initialize a new lock
entry’s commitSeqNo to that of the old one being transferred, or
take the minimum commitSeqNo if it is merging two lock entries.
Also, CreatePredicateLock should initialize commitSeqNo for to
InvalidSerCommitSeqNo instead of to 0. (I don’t think using 0 would
actually affect anything, but we should be consistent.) I also added
a couple of assertions I used to track this down: a lock’s
commitSeqNo should never be zero, and it should be
InvalidSerCommitSeqNo if and only if the lock is not held by
OldCommittedSxact. Dan Ports, to fix leak of predicate locks
reported by YAMAMOTO Takashi.

– Fix the size of predicate lock manager’s shared memory hash tables
at creation. This way they don’t compete with the regular lock
manager for the slack shared memory, making the behavior more

– On IA64 architecture, we check the depth of the register stack in
addition to the regular stack. The code to do that is platform and
compiler specific, add support for the HP-UX native compiler.

– Revert the patch to check if we’ve reached end-of-backup also when
doing crash recovery, and throw an error if not. hubert depesz
lubaczewski pointed out that that situation also happens in the
crash recovery following a system crash that happens during an
online backup. We might want to do something smarter in 9.1, like
put the check back for backups taken with pg_basebackup, but that’s
for another patch.

– On HP/UX, the structs used by ioctl(SIOCGLIFCONF) are named
differently than on other platforms, and only IPv6 addresses are
returned. Because of those two issues, fall back to
ioctl(SIOCGIFCONF) on HP/UX, so that it at least compiles and finds
IPv4 addresses. This function is currently only used for
interpreting samehost/samenet in pg_hba.conf, which isn’t that

– Reduce the initial size of local lock hash to 16 entries. The hash
table is seq scanned at transaction end, to release all locks, and
making the hash table larger than necessary makes that slower. With
very simple queries, that overhead can amount to a few percent of
the total CPU time used. At the moment, backend startup needs 6
locks, and a simple query with one table and index needs 3 locks. 16
is enough for even quite complicated transactions, and it will grow
automatically if it fills up.

– setlocale() on Windows doesn’t work correctly if the locale name
contains apostrophes or dots. There isn’t much hope of Microsoft
fixing it any time soon, it’s been like that for ages, so we better
work around it. So, map a few common Windows locale names known to
cause problems to aliases that work.

– On Windows, if the encoding implied by locale is not allowed as a
server-encoding, fall back to UTF-8. It happens at least with the
Chinese locale, which implies BIG5. This is safe, because on Windows
all locales are compatible with UTF-8.

Tom Lane pushed:

– Teach pattern_fixed_prefix() about collations. This is necessary,
not optional, now that ILIKE and regexes are collation aware —
else we might derive a wrong comparison constant for index optimized
pattern matches.

– Fix RI_Initial_Check to use a COLLATE clause when needed in its
query. If the referencing and referenced columns have different
collations, the parser will be unable to resolve which collation to
use unless it’s helped out in this way. The effects are sometimes
masked, if we end up using a non-collation-sensitive plan; but if we
do use a mergejoin we’ll see a failure, as recently noted by Robert
Haas. The SQL spec states that the referenced column’s collation
should be used to resolve RI checks, so that’s what we do. Note
however that we currently don’t append a COLLATE clause when writing
a query that examines only the referencing column. If we ever
support collations that have varying notions of equality, that will
have to be changed. For the moment, though, it’s preferable to
leave it off so that we can use a normal index on the referencing

– Be more wary of missing statistics in eqjoinsel_semi(). In
particular, if we don’t have real ndistinct estimates for both
sides, fall back to assuming that half of the left-hand rows have
join partners. This is what was done in 8.2 and 8.3 (cf
nulltestsel() in those versions). It’s pretty stupid but it won’t
lead us to think that an antijoin produces no rows out, as seen in
recent example from Uwe Schroeder.

– Suppress compiler warnings about “value computed is not used”. The
recent patch to remove gcc 4.6 warnings created some new ones, at
least on my rather old gcc version. Try to make everybody happy by
casting to “void” when we just want to discard the result.

– Pass collations to functions in FunctionCallInfoData, not FmgrInfo.
Since collation is effectively an argument, not a property of the
function, FmgrInfo is really the wrong place for it; and this
becomes critical in cases where a cached FmgrInfo is used for
varying purposes that might need different collation settings. Fix
by passing it in FunctionCallInfoData instead. In particular this
allows a clean fix for bug #5970 (record_cmp not working). This
requires touching a bit more code than the original method, but
nobody ever thought that collations would not be an invasive

– Fix broken pg_dump query. The 8.4 branch failed when talking to 7.0
servers. Per testing requested by Bruce.

– Add some useful cross-references to the CREATE EXTENSION reference
page. Per a suggestion from Josh Kupershmidt, though I modified his
patch quite a lot.

– Update time zone data files to tzdata release 2011f. DST law
changes in Chile, Cuba, Falkland Islands, Morocco, Samoa, Turkey.
Historical corrections for South Australia, Alaska, Hawaii.

– Ensure mark_dummy_rel doesn’t create dangling pointers in
RelOptInfos. When we are doing GEQO join planning, the current
memory context is a short-lived context that will be reset at the
end of geqo_eval(). However, the RelOptInfos for base relations are
set up before that and then re-used across many GEQO cycles. Hence,
any code that modifies a baserel during join planning has to be
careful not to put pointers to the short-lived context into the
baserel struct. mark_dummy_rel got this wrong, leading to
easy-to-reproduce-once-you-know-how crashes in 8.4, as reported
off-list by Leo Carson of SDSC. Some improvements made in 9.0 make
it difficult to demonstrate the crash in 9.0 or HEAD; but there’s no
doubt that there’s still a risk factor here, so patch all branches
that have the function. (Note: 8.3 has a similar function, but it’s
only applied to joinrels and thus is not a hazard.)

– Update release notes for releases 9.0.4, 8.4.8, 8.3.15, and 8.2.21.

– Guard against incoming rowcount estimate of NaN in cost_mergejoin().
Although rowcount estimates really ought not be NaN, a bug elsewhere
could perhaps result in that, and that would cause Assert failure in
cost_mergejoin, which I believe to be the explanation for bug #5977
from Anton Kuznetsov. Seems like a good idea to expend a couple
more cycles to prevent that, even though the real bug is elsewhere.
Not back-patching, though, because we don’t encourage running
production systems with Asserts on.

– Suppress unused-function warning on non-WIN32 builds.

– Prevent incorrect updates of pg_index while reindexing pg_index
itself. The places that attempt to change pg_index.indcheckxmin
during a reindexing operation cannot be executed safely if pg_index
itself is the subject of the operation. This is the explanation for
a couple of recent reports of VACUUM FULL failing with
ERROR: duplicate key value violates unique constraint “pg_index_indexrelid_index”
DETAIL: Key (indexrelid)=(2678) already exists.
However, there isn’t any real need to update indcheckxmin in such a
situation, if we assume that pg_index can never contain a truly
broken HOT chain. This assumption holds if new indexes are never
created on it during concurrent operations, which is something we
don’t consider safe for any system catalog, not just pg_index.
Accordingly, modify the code to not manipulate indcheckxmin when
reindexing any system catalog. Back-patch to 8.3, where HOT was
introduced. The known failure scenarios involve 9.0-style VACUUM
FULL, so there might not be any real risk before 9.0, but let’s not
assume that.

– Clean up collation processing in prepunion.c. This area was a few
bricks shy of a load, and badly under-commented too. We have to
ensure that the generated targetlist entries for a set-operation
node expose the correct collation for each entry, since higher-level
processing expects the tlist to reflect the true ordering of the
plan’s output. This hackery wouldn’t be necessary if
SortGroupClause carried collation info … but making it do so would
inject more pain in the parser than would be saved here. Still, we
might want to rethink that sometime.

– Simplify reindex_relation’s API. For what seem entirely historical
reasons, a bitmask “flags” argument was recently added to
reindex_relation without subsuming its existing boolean argument
into that bitmask. This seems a bit bizarre, so fold them together.

– Add an Assert that indexam.c isn’t used on an index awaiting
reindexing. This might have caught the recent embarrassment over
trying to modify pg_index while its indexes were being rebuilt.
Noah Misch

– foreach() and list_delete() don’t mix. Fix crash when releasing
duplicate entries in the encoding conversion cache list, caused by
releasing the current entry of the list being chased by foreach().
We have a standard idiom for handling such cases, but this loop
wasn’t using it. This got broken in my recent rewrite of GUC assign
hooks. Not sure how I missed this when testing the modified code,
but I did. Per report from Peter.

– Support a COLLATE clause in plpgsql variable declarations. This
allows the usual rules for assigning a collation to a local variable
to be overridden. Per discussion, it seems appropriate to support
this rather than forcing all local variables to have the
argument-derived collation.

– Add check for matching column collations in ALTER TABLE … INHERIT.
The other DDL operations that create an inheritance relationship
were checking for collation match already, but this one got missed.
Also fix comments that failed to mention collation checks.

– Fix pg_dump to handle collations applied to columns of composite
types. CREATE TYPE and ALTER TYPE ADD ATTRIBUTE handle this, so I
suppose it’s an intended feature, but pg_dump didn’t know about it.

– Document COLLATE option in CREATE TYPE reference page. Curiously,
it was already documented in ALTER TYPE ADD ATTRIBUTE, but not here.

– Fix assorted infelicities in collation handling in psql’s
describe.c. In \d, be more careful to print collation only if it’s
not the default for the column’s data type. Avoid assuming that the
name “default” is magic. Fix \d on a composite type so that it will
print per-column collations. It’s no longer the case that a
composite type cannot have modifiers. (In consequence, the expected
outputs for composite-type regression tests change.) Fix \dD so that
it will print collation for a domain, again only if it’s not the
same as the base type’s collation.

Peter Eisentraut pushed:

– Clean up most -Wunused-but-set-variable warnings from gcc 4.6. This
warning is new in gcc 4.6 and part of -Wall. This patch cleans up
most of the noise, but there are some still warnings that are
trickier to remove.

– Translation updates.

– Rename pg_regress option –multibyte to –encoding. Also refactor
things a little bit so that the same methods for setting test locale
and encoding can be used everywhere.

– Set client encoding explicitly in plpython_unicode test. This will
(hopefully) eliminate the need for the plpython_unicode_0.out
expected file.

Andrew Dunstan pushed:

– Don’t make “replication” magical as a user name, only as a database
name, in pg_hba.conf. Per gripe from Josh Berkus. Backported from
commit ed557a373c406bbb2a1843544ebbd856ca4cac47.

Bruce Momjian pushed:

– Fix pg_upgrade crash. Fix pg_upgrade crash in 9.0 caused by a new
cluster database that doesn’t exist in the old cluster; instead
throw an error. This was reported to me by EnterpriseDB testing
staff. This bug does not exist in git head.

Robert Haas pushed:

– Avoid incorrectly granting replication to roles created with
NOSUPERUSER. Andres Freund

– Fix toast table creation. Instead of using slightly-too-clever
heuristics to decide when we must create a TOAST table, just check
whether one is needed every time the table is altered. Checking
whether a toast table is needed is cheap enough that we needn’t
worry about doing it on every ALTER TABLE command, and the previous
coding is apparently prone to accidental breakage: commit
04e17bae50a73af524731fa11210d5c3f7d8e1f9 broken ALTER TABLE .. SET
STORAGE, which moved some actions from AT_PASS_COL_ATTRS to
AT_PASS_MISC, and commit 6c5723998594dffa5d47c3cf8c96ccf89c033aae
broke ALTER TABLE .. ADD COLUMN by changing the way that adding
columns recurses into child tables. Noah Misch, with one comment
change by me

– Remove obsolete comment. The lock level for adding a parent table
is now ShareUpdateExclusiveLock; see commit
fbcf4b92aa64d4577bcf25925b055316b978744a. This comment didn’t get
updated to match, but it doesn’t seem important to mention this
detail here, so rather than updating it now, just take it out.

– Advise Debian/Ubuntu users to use openjade1.3. The latest openjade
packages for Ubuntu 10.10 seg fault when building our documentation.
Josh Berkus

Marc Fournier pushed:

– Tag 9.0.4, 8.4.8, 8.3.15, and 8.2.21.

Magnus Hagander pushed:

– Note that Bison on GnuWin32 has trouble with paths with spaces.
Peter Eisentraut

– Specify which versions of the Platform SDK are supported. Anything
including Visual Studio 2010 compilers is not yet supported for
building on Windows.

== Rejected Patches (for now) ==

No one was disappointed this week 🙂

== Pending Patches ==

Roman Zotov sent in another revision of the patch to turn PREFERRED
for type from a boolean to an int2, which allows for an expression of

Robert Haas sent in a patch to fix a bug in recoveryStopsHere().

Greg Smith sent in a patch to remove some of the magic from running

Andrew Dunstan sent in two revisions of a patch to remove pgindent
magic in different ways from Greg Smith’s.

Comments are closed.