== WöchentlicherPostgreSQL Newsletter - 17. Mai2009

Der Originalartikel befindet sich unter:
http://www.postgresql.org/community/weeklynews/pwn20090517


== Wöchentlicher PostgreSQL Newsletter - 17. Mai 2009 ==

pgDay San Jose wird am Sonntag den 19. Juni 2009 stattfinden,
unmittelbar vor der OSCON. Reiche deine Vorträge bis zum 8. Juni 2009
an conference-sf-speakers AT pgfoundry DOT org ein und finde bis zum
20. Juni 2009 heraus, ob dein Vortrag akzeptiert wurde.
http://www.postgresql.org/about/news.1082

Yet Another Perl Conference 10 findet in Pittsburgh vom 22. bis 24. Juni
statt, mit Vorträgen von David Fetter und Lehrgängen vom bekannten
Instruktor Joe Celko.
http://yapc10.org

PGCon 2009 findet diese Woche in Ottawa statt. Erwarte eine Menge
Neuigkeiten.

== PostgreSQL 8.4 Feature der Woche ==

Common Table Expressions. Mit einer einfachen Syntax kannst du deinen
eigenen einmal nutzbaren View zur Laufzeit erstellen, der Rekursion
enthalten darf. Damit sind Baumstrukturen in Reichweite.

== PostgreSQL Tipp der Woche ==

Nutze niemals fsync=3Doff, außer du kannst es dir leisten, deinen gesa=
mten
Datenbankcluster von Anfang an neu aufzusetzen. Wenn die
Transaktionslogs die Performance zu sehr beeinträchtigen, nutze
statt dessen synchronous_commit=3Dfalse.

== PostgreSQL Jobs im Mai ==

http://archives.postgresql.org/pgsql-jobs/2009-05/threads.ph p

== PostgreSQL Lokal ==

Gabriele Bartolini von 2ndQuadrant Italien wird am 20. Mai in Pisa
an der Veranstaltung "Open Source: Unternehmen treffen die Studenten",
organisiert von den Toskana Open Source Software Werkstätten,
teilnehmen. Mehr Informationen (aut italienisch):
http://www.tosslab.it/open-source-aziende-e-studenti-si-inco ntrano

PGCon 2009 wird vom 21. bis 22. Mai 2009 in Ottawa an der Universität
von Ottawa stattfinden. Dem gehen zwei Tage mit Tutorials vom 19. bis
20. Mai 2009 voraus.
http://www.pgcon.org/2009/

PgDay Florianopolis wird am 22. Mai stattfinden. Kontaktiere Dickson S.
Guedes (guedes AT guedesoft DOT net) um teilzunehmen oder einen Vortrag
einzureichen.
http://www.postgresql.org.br/eventos/pgday/sc

PGDay Junin / Buenos Aires Unnoba wird am 6. Juni 2009 stattfinden.
http://www.arpug.com.ar/trac/wiki/PgDayUnnoba

Termin vormerken: pgDay San Jose, am Sonntag dem 19. Juli unmittelbar
vor der OSCON. CfP und mehr Informationen bald.

PGCon Brasilien wird am 23.-24. Oktober 2009 auf dem Unicamp in
Campinas, Sao Paulo, stattfinden.

PGDay.EU 2009 wird an der Telecom ParisTech Universität in Paris,
Frankreich, am 6. und 7. Nivember 2009 stattfinden.
http://www.pgday.eu/

== PostgreSQL in den News ==

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

Dieser wöchentliche PostgreSQL Newsletter wurde erstellt von David
Fetter und Josh Berkus.

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 ==

Tom Lane committed:

- Fix cost_nestloop and cost_hashjoin to model the behavior of semi
and anti joins a bit better, ie, understand the differing cost
functions for matched and unmatched outer tuples. There is more
that could be done in cost_hashjoin but this already helps a great
deal. Per discussions with Robert Haas.

- In pgsql/src/bin/pg_dump/pg_dumpall.c, adjust pg_dumpall so that it
emits ENCODING, LC_COLLATE, and LC_CTYPE options in its CREATE
DATABASE commands only for databases that have settings different
from the installation defaults. This is a low-tech method of
avoiding unnecessary platform dependencies in dump files.
Eventually we ought to have a platform-independent way of specifying
LC_COLLATE and LC_CTYPE, but that's not going to happen for 8.4, and
this patch at least avoids the issue for people who aren't setting
up per-database locales. ENCODING doesn't have the platform
dependency problem, but it seems consistent to make it act the same
as the locale settings.

- In pgsql/src/backend/optimizer/util/predtest.c, make a marginal
performance improvement in predicate_implied_by and
predicate_refuted_by: if either top-level input is a single-element
list, reduce it to its lone member before proceeding. This avoids a
useless level of AND-recursion within the recursive proof routines.
It's worth doing because, for example, if the clause is a
100-element list and the predicate is a 1-element list then we'd
otherwise strip the predicate's list structure 100 times as we
iterate through the clause. It's only needed at top level because
there won't be any trivial ANDs below that --- this situation is an
artifact of the decision to represent even single-item conditions as
Lists in the "implicit AND" format, and that format is only used at
the top level of any predicate or restriction condition.

- In pgsql/src/backend/optimizer/util/predtest.c, partially revert my
patch of 2008-11-12 that installed a limit on the number of AND/OR
clause branches that predtest.c would attempt to deal with. As
noted in bug #4721, that change disabled proof attempts for sizes of
problems that people are actually expecting it to work for. The
original complaint it was trying to solve was O(N^2) behavior for
long IN-lists, so let's try applying the limit to just
ScalarArrayOpExprs rather than everything. Another case of "foolish
consistency" I fear. Back-patch to 8.2, same as the previous patch
was.

- Do some minor code refactoring in preparation for changing the APIs
of find_inheritance_children() and find_all_inheritors(). I got
annoyed that these are buried inside the planner but mostly used
elsewhere. So, create a new file catalog/pg_inherits.c and put them
there, along with a couple of other functions that search
pg_inherits. The code that modifies pg_inherits is (still) in
tablecmds.c --- it's kind of entangled with unrelated code that
modifies pg_depend and other stuff, so pulling it out seemed like a
bigger change than I wanted to make right now. But this file
provides a natural home for it if anyone ever gets around to that.
This commit just moves code around; it doesn't change anything,
except I succumbed to the temptation to make a couple of trivial
optimizations in typeInheritsFrom().

- Modify find_inheritance_children() and find_all_inheritors() to add
the ability to lock relations as they scan pg_inherits, and to
ignore any relations that have disappeared by the time we get lock
on them. This makes uses of these functions safe against concurrent
DROP operations on child tables: we will effectively ignore any
just-dropped child, rather than possibly throwing an error as in
recent bug report from Thomas Johansson (and similar past
complaints). The behavior should not change otherwise, since the
code was acquiring those same locks anyway, just a little bit later.
An exception is LockTableCommand(), which is still behaving
unsafely; but that seems to require some more discussion before we
change it.

- Fix LOCK TABLE to eliminate the race condition that could make it
give weird errors when tables are concurrently dropped. To do this
we must take lock on each relation before we check its privileges.
The old code was trying to do that the other way around, which is a
bit pointless when there are lots of other commands that lock
relations before checking privileges. I did keep it checking each
relation's privilege before locking the next relation, which is a
detail that ALTER TABLE isn't too picky about.

- In pgsql/src/backend/utils/adt/xml.c, fix intratransaction memory
leaks in xml_recv, xmlconcat, xmlroot, and xml_parse, all arising
from the same sloppy usage of parse_xml_decl. The original coding
had that function returning its output string parameters in the
libxml context, which is long-lived, and all but one of its callers
neglected to free the strings afterwards. The easiest and most
bulletproof fix is to return the strings in the local palloc context
instead, since that's short-lived. This was only costing a dozen or
two bytes per function call, but that adds up fast if the function
is called repeatedly ... Noted while poking at the more general
problem of what to do with our libxml memory allocation hooks.
Back-patch to 8.3, which has the identical coding.

- In pgsql/doc/src/sgml/release-8.4.sgml, update release notes for
changes through 2009-05-11. Also some minor copy-editing and
reordering of items.

- Rewrite xml.c's memory management (yet again). Give up on the idea
of redirecting libxml's allocations into a Postgres context.
Instead, just let it use malloc directly, and add PG_TRY blocks as
needed to be sure we release libxml data structures in error
recovery code paths. This is ugly but seems much more likely to
play nicely with third-party uses of libxml, as seen in recent
trouble reports about using Perl XML facilities in pl/perl and bug
#4774 about contrib/xml2. I left the code for allocation
redirection in place, but it's only built/used if you #define
USE_LIBXMLCONTEXT. This is because I found it useful to corral
libxml's allocations in a palloc context when hunting for libxml
memory leaks, and we're surely going to have more of those in the
future with this type of approach. But we don't want it turned on
in a normal build because it breaks exactly what we need to fix. I
have not re-indented most of the code sections that are now wrapped
by PG_TRY(); that's for ease of review. pg_indent will fix it.
This is a pre-existing bug in 8.3, but I don't dare back-patch this
change until it's gotten a reasonable amount of field testing.

- In pgsql/doc/src/sgml/func.sgml, remove a useless backslash from a
pattern-match example. Michael Toews.

- In pgsql/src/backend/rewrite/rewriteDefine.c, add checks to
DefineQueryRewrite() to prohibit attaching rules to relations that
aren't RELKIND_RELATION or RELKIND_VIEW, and to disallow attaching
rules to system relations unless allowSystemTableMods is on. This
is to make the behavior of CREATE RULE more like CREATE TRIGGER,
which disallows the comparable cases. Per discussion of bug #4808.

- In pgsql/src/backend/access/transam/xlog.c, improve a couple of
comments.

- In pgsql/doc/src/sgml/pgstandby.sgml, clean up overly hasty docs
patch for pg_standby.

- In pgsql/doc/src/sgml/release-8.4.sgml, update release notes to
today.

- In pgsql/src/backend/access/transam/recovery.conf.sample, include
recovery_end_command in recovery.conf.sample. Per suggestion of
Jaime Casanova.

- Fix all the server-side SIGQUIT handlers (grumble ... why so many
identical copies?) to ensure they really don't run
proc_exit/shmem_exit callbacks, as was intended. I broke this
behavior recently by installing atexit callbacks without thinking
about the one case where we truly don't want to run those callback
functions. Noted in an example from Dave Page.

- In pgsql/src/backend/libpq/pg_ident.conf.sample, improve comments in
pg_ident.conf.sample.

- In pgsql/doc/src/sgml/client-auth.sgml, make an editorial pass over
the Client Authentication material.

- In pgsql/doc/src/sgml/storage.sgml, minor editorialization on
storage.sgml's documentation of free space maps.

- In pgsql/doc/src/sgml/maintenance.sgml, minor copy-editing for
description of partial-table vacuuming.

Magnus Hagander committed:

- In pgsql/src/backend/libpq/be-secure.c, support SSL certificate
chains in the server certificate file. Andrew (RhodiumToad) Gierth.

- In pgsql/doc/src/sgml/release-8.4.sgml, edit the SSL and Kerberos
parts of the release notes a bit, and add a note about the
certificates chains patch just applied.

- In pgsql/doc/src/sgml/release-8.4.sgml, move crypt auth comment to
proper section. Add some details about the name=3Dvalue format of
auth options.

Heikki Linnakangas committed:

- Add recovery_end_command option to recovery.conf.
recovery_end_command is run at the end of archive recovery,
providing a chance to do external cleanup. Modify pg_standby so that
it no longer removes the trigger file, that is to be done using the
recovery_end_command now. Provide a "smart" failover mode in
pg_standby, where we don't fail over immediately, but only after
recovering all unapplied WAL from the archive. That gives you zero
data loss assuming all WAL was archived before failover, which is
what most users of pg_standby actually want. recovery_end_command
by Simon Riggs, pg_standby changes by Fujii Masao and myself.

- In pgsql/doc/src/sgml/release-8.4.sgml, add a note to release notes
about the smart failover mode in pg_standby.

Alvaro Herrera committed:

- Translation updates.

Marc Fournier committed:

- commit for BETA2.

== Abgelehnte Patches (bis jetzt) ==

Dickson S. Guedes's patch to change charset.sgml. CVS failure.

== Eingesandte Patches ==

Damien Clochard sent in another revision of the patch to add inherited
tables to \d+ output.

Khee Chin sent in three more revision of his patch to add index type
and index expression to \d output in psql.

ITAGAKI Takahiro sent in a WIP patch to allow the FORCE QUOTE and
FORCE NOT NULL options in COPY ... CSV not to take a column name as
argument, and for absence of that argument to mean that the options
would apply to all columns.

Pavel Stehule sent in two revisions of the GROUPING SETS patch.

KaiGai Kohei sent in another revision of his SE-PostgreSQL patches.

Euler Taveira de Oliveira sent in a patch to use ngettext on some more
plural forms.

--=20
Andreas 'ads' Scherbaum
Deutsche PostgreSQL User Group: http://www.pgug.de
DPWN: http://andreas.scherbaum.la/blog/categories/18-PWN

--=20
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