== WöchentlicherPostgreSQL Newsletter - 01.November 2009

Der Originalartikel befindet sich unter:

http://www.postgresql.org/community/weeklynews/pwn20091101



== Wöchentlicher PostgreSQL Newsletter - 01. November 2009 ==

PostgreSQL 8.5alpha2 ist erschienen. Beginne mit dem Testen in deinem
Environment.
http://www.postgresql.org/developer/alpha

== PostgreSQL Produkt Neuigkeiten ==

pgtune 0.9.2, ein System zum Tunen der grundlegenden PostgreSQL-
Konfigurationsdateien, ist erschienen.
http://pgfoundry.org/projects/pgtune/

== PostgreSQL Lokal ==

LISA 09, die Large Installation and Systems Administration Konferenz,
findet vom 1. bis 6. November 2009 statt. Es wird einen PostgreSQL
Stand am Mittwoch und Donnerstag geben.
http://www.usenix.org/event/lisa09/

PGDay.EU 2009 will be at Telecom ParisTech in Paris, France on
November 6-7, 2009.
http://www.pgday.eu/

OpenSQL Camp in Portland sucht Sponsoren. Bereite deine Reisepläne
jetzt vor! :)
http://www.chesnok.com/daily/2009/07/29/opensql-camp-comes-t o-portland-nove=
mber-14-15-2009/

Die 10. jährliche JPUG Konferenz findet am 20-21. November 2009 in
Tokio, Japan, statt.
http://archives.postgresql.org/pgsql-announce/2009-05/msg000 18.php

FOSDEM 2010 findet am 6. und 7. Februar 2010 in Brüssel,
Belgien statt.
http://www.fosdem.org/

Die Chemnitzer Linuxtage finden am 13. und 14. März in
Chemnitz, Deutschland statt.
http://chemnitzer.linux-tage.de/

== PostgreSQL in den News ==

Planet PostgreSQL: http://planet.postgresql.org/

Dieser wöchentliche PostgreSQL Newsletter wurde erstellt von David
Fetter.

Sende Neuigkeiten und Ankündigungen bis Sonntag, 15 Uhr Pazifischer
Zeit. Bitte sende englische Beiträge an david@fetter.org, deutsche an
pwn@pgug.de, italienische an pwn@itpug.org.

== Angewandte Patches ==

Heikki Linnakangas committed:

- Fix range check in date_recv that tried to limit accepted values to
only those accepted by date_in(). I confused Julian day numbers and
number of days since the postgres epoch 2000-01-01 in the original
patch. I just noticed that it's still easy to get such out-of-range
values into the database using to_date or +- operators, but this
patch doesn't do anything about those functions. Per report from
James Pye.

Peter Eisentraut committed:

- In pgsql/src/test/regress/GNUmakefile, check errors in for loop.

- Simplify a few makefile rules since install-sh can now install
multiple files in one run.

- In pgsql/GNUmakefile.in, remove some leftovers of split tarball
support.

Alvaro Herrera committed:

- In pgsql/doc/src/sgml/ref/create_table.sgml, fix documentation on
the toast.fillfactor reloption: it doesn't exist. Per note from
Zoltan Boszormenyi.

Tom Lane committed:

- Make FOR UPDATE/SHARE in the primary query not propagate into WITH
queries; for example in WITH w AS (SELECT * FROM foo) SELECT * FROM
w, bar ... FOR UPDATE the FOR UPDATE will now affect bar but not
foo. This is more useful and consistent than the original 8.4
behavior, which tried to propagate FOR UPDATE into the WITH query
but always failed due to assorted implementation restrictions. Even
though we are in process of removing those restrictions, it seems
correct on philosophical grounds to not let the outer query's FOR
UPDATE affect the WITH query. In passing, fix isLockedRel which
frequently got things wrong in nested-subquery cases: "FOR UPDATE OF
foo" applies to an alias foo in the current query level, not
subqueries. This has been broken for a long time, but it doesn't
seem worth back-patching further than 8.4 because the actual
consequences are minimal. At worst the parser would sometimes get
RowShareLock on a relation when it should be AccessShareLock or vice
versa. That would only make a difference if someone were using
ExclusiveLock concurrently, which no standard operation does, and
anyway FOR UPDATE doesn't result in visible changes so it's not
clear that the someone would notice any problem. Between that and
the fact that FOR UPDATE barely works with subqueries at all in
existing releases, I'm not excited about worrying about it.

- In pgsql/src/backend/commands/trigger.c, fix AfterTriggerSaveEvent
to use a test and elog, not just Assert, to check that it's called
within an AfterTriggerBeginQuery/AfterTriggerEndQuery pair. The RI
cascade triggers suppress that overhead on the assumption that they
are always run non-deferred, so it's possible to violate the
condition if someone mistakenly changes pg_trigger to mark such a
trigger deferred. We don't really care about supporting that, but
throwing an error instead of crashing seems desirable. Per report
from Marcelo Costa.

- When FOR UPDATE/SHARE is used with LIMIT, put the LockRows plan node
underneath the Limit node, not atop it. This fixes the old problem
that such a query might unexpectedly return fewer rows than the
LIMIT says, due to LockRows discarding updated rows. There is a
related problem that LockRows might destroy the sort ordering
produced by earlier steps; but fixing that by pushing LockRows below
Sort would create serious performance problems that are unjustified
in many real-world applications, as well as potential deadlock
problems from locking many more rows than expected. Instead, keep
the present semantics of applying FOR UPDATE after ORDER BY within a
single query level; but allow the user to specify the other way by
writing FOR UPDATE in a sub-select. To make that work, track
whether FOR UPDATE appeared explicitly in sub-selects or got pushed
down from the parent, and don't flatten a sub-select that contained
an explicit FOR UPDATE.

- Fix AcquireRewriteLocks to be sure that it acquires the right lock
strength when FOR UPDATE is propagated down into a sub-select
expanded from a view. Similar bug to parser's isLockedRel issue
that I fixed yesterday; likewise seems not quite worth the effort to
back-patch.

- In pgsql/src/bin/psql/describe.c, fix \df to re-allow regexp special
characters in the function name pattern. This has always worked, up
until somebody's thinko here:
http://archives.postgresql.org/pgsql-committers/2009-04/msg0 0233.php
Per bug #5143 from Piotr Wolinski.

- In pgsql/src/backend/utils/adt/ruleutils.c, un-break EXPLAIN for
Append plans. I messed this up a few days ago while adding the
ModifyTable node type --- I had been thinking ModifyTable should
replace Append as a special case in push_plan(), but actually both
of them have to be special-cased.

- In pgsql/src/backend/executor/nodeHash.c, make the overflow guards
in ExecChooseHashTableSize be more protective. The original coding
ensured nbuckets and nbatch didn't exceed INT_MAX, which while not
insane on its own terms did nothing to protect subsequent code like
"palloc(nbatch * sizeof(BufFile *))". Since enormous join size
estimates might well be planner error rather than reality, it seems
best to constrain the initial sizes to be not more than
work_mem/sizeof(pointer), thus ensuring the allocated arrays don't
exceed work_mem. We will allow nbatch to get bigger than that
during subsequent ExecHashIncreaseNumBatches calls, but we should
still guard against integer overflow in those palloc requests. Per
bug #5145 from Bernt Marius Johnsen. Although the given test case
only seems to fail back to 8.2, previous releases have variants of
this issue, so patch all supported branches.

- Implement parser hooks for processing ColumnRef and ParamRef nodes,
as per my recent proposal. As proof of concept, remove knowledge of
Params from the core parser, arranging for them to be handled
entirely by parser hook functions. It turns out we need an
additional hook for that --- I had forgotten about the code that
handles inferring a parameter's type from context. This is a
preliminary step towards letting plpgsql handle its variables
through parser hooks. Additional work remains to be done to expose
the facility through SPI, but I think this is all the changes needed
in the core parser.

- In pgsql/src/pl/plperl/plperl.c, ensure the previous Perl
interpreter selection is restored upon exit from
plperl_call_handler, in both the normal and error-exit paths. Per
report from Alexey Klyukin.

- Fix two serious bugs introduced into hash indexes by the 8.4 patch
that made hash indexes keep entries sorted by hash value. First,
the original plans for concurrency assumed that insertions would
happen only at the end of a page, which is no longer true; this
could cause scans to transiently fail to find index entries in the
presence of concurrent insertions. We can compensate by teaching
scans to re-find their position after re-acquiring read locks.
Second, neither the bucket split nor the bucket compaction logic had
been fixed to preserve hashvalue ordering, so application of either
of those processes could lead to permanent corruption of an index,
in the sense that searches might fail to find entries that are
present. This patch fixes the split and compaction logic to
preserve hashvalue ordering, but it cannot do anything about
pre-existing corruption. We will need to recommend reindexing all
hash indexes in the 8.4.2 release notes. To buy back the
performance loss hereby induced in split and compaction, fix them to
use PageIndexMultiDelete instead of retail PageIndexDelete
operations. We might later want to do something with qsort'ing the
page contents rather than doing a binary search for each insertion,
but that seemed more invasive than I cared to risk in a back-patch.
Per bug #5157 from Jeff Janes and subsequent investigation.

- Department of second thoughts: after studying index_getnext() a bit
more I realize that it can scribble on scan->xs_ctup.t_self while
following HOT chains, so we can't rely on that to stay valid between
hashgettuple() calls. Introduce a private variable in
HashScanOpaque, instead.

== Abgelehnte Patches (bis jetzt) ==

No one was disappointed this week :-)

== Eingesandte Patches ==

Michael Paquier sent in another revision of the patch to allow pgbench
to issue shell commands.

ITAGAKI Takahiro sent in another patch to add VACUUM ( FULL [ INPLACE
| REPLACE ] ).

Jeff Davis sent in two more revisions of the operator exclusion
constraints patch.

Peter Eisentraut sent in a patch to make \d+ work better for views in
psql.

Shrish Purohit sent in a patch intended to automate partitioning.

Peter Eisentraut sent in a patch to fix an issue where PL/PythonU can
segfault.

Peter Eisentraut sent in a patch to fix an issue with PL/PythonU's
elog output.

Roger Leigh sent in another patch to make an "ascii clean" format for
psql output.

Hitoshi Harada sent in a patch which implements PL/Javascript using
Google's V8 Javascript engine.

ITAGAKI Takahiro sent in a WIP patch to implement table partitioning
in SQL.

Andreas Freund sent in a patch which makes certain tsearch operations
more efficient.

--
Andreas 'ads' Scherbaum
Deutsche PostgreSQL User Group: http://www.pgug.de/
DPWN: http://andreas.scherbaum.la/blog/categories/18-PWN

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