== WöchentlicherPostgreSQL Newsletter - 08.November 2009

Der Originalartikel befindet sich unter:

http://www.postgresql.org/community/weeklynews/pwn20091108



== Wöchentlicher PostgreSQL Newsletter - 08. November 2009 ==

PGDay.EU is over, mit Plänen für das nächste Jahr in den
Niederlanden.

PostgreSQL 8.5alpha2 RPMs sind jetzt verfügbar. Danke, Devrim!
http://yum.pgsqlrpms.org/howtuyum.php

== PostgreSQL Produkt Neuigkeiten ==

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

== PostgreSQL Jobs im November ==

http://archives.postgresql.org/pgsql-jobs/2009-11/threads.ph p

== PostgreSQL Lokal ==

Das OpenSQL Camp findet am 14-15. November 2009 in Portland, OR statt.
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

Stefan Keller gibt einen Kurs "Einführung in PostGIS/PostgreSQL" an
der HSR Hochschule für Technik Rapperswil am 14. Januar 2010
in Zürich, Schweiz.
http://www.gis.hsr.ch/wiki/Agenda

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 ==

Peter Eisentraut committed:

- Fix obscure segfault condition in PL/Python In PLy_output(), when
the elog() call in the TRY branch throws an exception (this can
happen when a statement timeout kicks in, for example), the
PyErr_SetString() call in the CATCH branch can cause a segfault,
because the Py_XDECREF(so) call before it releases memory that is
still used by the sv variable that PyErr_SetString() uses as
argument, because sv points into memory owned by so. Backpatched
back to 8.0, where this code was introduced. I also threw in a
couple of volatile declarations for variables that are used before
and after the TRY. I don't think they caused the crash that I
observed, but they could become issues.

- In pgsql/src/bin/psql/describe.c, show view definition only with
\d+, not with \d The rationale is that view definitions tend to be
long and obscure the main information about the view.

- Improve PL/Python elog output. When the elog functions (plpy.info
etc.) get a single argument, just print that argument instead of
printing the single-member tuple like ('foo',).

- Fix regression tests for psql \d view patch.

- Build bzip2 tarball in dist target as well.

- In pgsql/src/backend/postmaster/syslogger.c, reenable -> re-enable
Pointed out by Debian's lintian.

Heikki Linnakangas committed:

- In pgsql/src/backend/commands/tablecmds.c, allow rewriting ALTER
TABLE to skip WAL logging. Itagaki Takahiro, with small changes by
me and Simon.

- In pgsql/contrib/pg_standby/pg_standby.c, disable triggering
failover with a signal in pg_standby on Windows, because Windows
doesn't do signal processing like other platforms do. It never
really worked, but recent changes to the signal handling made it
crash. This fixes bug #4961. Patch by Fujii Masao.

Tom Lane committed:

- Add support for invoking parser callback hooks via SPI and in cached
plans. As proof of concept, modify plpgsql to use the hooks.
plpgsql is still inserting $n symbols textually, but the "back end"
of the parsing process now goes through the ParamRef hook instead of
using a fixed parameter-type array, and then execution only fetches
actually-referenced parameters, using a hook added to ParamListInfo.
Although there's a lot left to be done in plpgsql, this already
cures the "if (TG_OP =3D 'INSERT' and NEW.foo ...)" problem, as
illustrated by the changed regression test.

- In pgsql/src/backend/parser/gram.y, make expression locations for
LIKE and SIMILAR TO constructs uniformly point at the first keyword
of the expression, rather than drawing a rather artificial
distinction between the ESCAPE subclause and the rest. Per gripe
from Gokulakannan Somasundaram and subsequent discusssion.

- Rename some encoding conversion modules to keep pathnames in our
source tarballs under 100 characters. This should avoid failures
with certain untarring tools (WinZip and Midnight Commander have
been mentioned as likely suspects). Per my proposal of yesterday.
catversion bumped since the initial contents of pg_proc change.

- Allow binary-coercible cases in ri_HashCompareOp; there are some
such cases that are not handled by find_coercion_pathway, notably
composite->RECORD. Now that 8.4 supports composites as primary
keys, it's worth dealing with this case.

- Remove plpgsql's RENAME declaration, which has bizarre and mostly
nonfunctional behavior, and is so little used that no one has been
interested in fixing it. To ensure that possible uses are covered,
remove the ALIAS declaration's arbitrary restriction that only $n
identifiers can be aliased. (We could alternatively make RENAME act
just like ALIAS, but per discussion having two different ways to do
the same thing is probably more confusing than helpful.)

- Don't treat NEW and OLD as reserved words anymore. For the purposes
of rules it works just as well to have them be ordinary identifiers,
and this gets rid of a number of ugly special cases. Plus we aren't
interfering with non-rule usage of these names. catversion bump
because the names change internally in stored rules.

- Change plpgsql from using textual substitution to insert variable
references into SQL expressions, to using the newly added parser
callback hooks. This allows us to do the substitutions in a more
semantically-aware way: a variable reference will only be recognized
where it can validly go, ie, a place where a column value or
parameter would be legal, instead of the former behavior that would
replace any textual match including table names and column aliases
(leading to syntax errors later on). A release-note-worthy fine
point is that plpgsql variable names that match fully-reserved words
will now need to be quoted. This commit preserves the former
behavior that variable references take precedence over any possible
match to a column name. The infrastructure is in place to support
the reverse precedence or throwing an error on ambiguity, but those
behaviors aren't accessible yet. Most of the code changes here are
associated with making the namespace data structure persist so that
it can be consulted at runtime, instead of throwing it away at the
end of initial function parsing. The plpgsql scanner is still doing
name lookups, but that behavior is now irrelevant for SQL
expressions. A future commit will deal with removing unnecessary
lookups.

- Rearrange plpgsql parsing to simplify and speed it up a bit. 1.
Pull the responsibility for %TYPE and %ROWTYPE out of the scanner,
letting read_datatype manage it instead. 2. Avoid unnecessary
scanner-driven lookups of plpgsql variables in places where it's not
needed, which is actually most of the time; we do not need it in
DECLARE sections nor in text that is a SQL query or expression. 3.
Rationalize the set of token types returned by the scanner:
distinguishing T_SCALAR, T_RECORD, T_ROW seems to complicate the
grammar in more places than it simplifies it, so merge these into
one token type T_DATUM; but split T_ERROR into T_DBLWORD and
T_TRIPWORD for clarity and simplicity of later processing. Some of
this will need to be revisited again when we try to make plpgsql use
the core scanner, but this patch gets some of the bigger stumbling
blocks out of the way.

- Remove ancient text file containing plpgsql installation
instructions. This was long ago superseded by the standard build
process and main SGML documentation.

- Modernize plpgsql's handling of parse locations, making it look a
lot more like the core parser's code. In particular, track
locations at the character rather than line level during parsing,
allowing many more parse-time error conditions to be reported with
precise error pointers rather than just "near line N". Also,
exploit the fact that we no longer need to substitute $N for
variable references by making extracted SQL queries and expressions
be exact copies of subranges of the function text, rather than
having random whitespace changes within them. This makes it
possible to directly map parse error positions from the core parser
onto positions in the function text, which lets us report them
without the previous kluge of showing the intermediate
internal-query form. (Later it might be good to do that for core
parse-analysis errors too, but this patch is just touching plpgsql's
lexer/parser, not what happens at runtime.) In passing, make
plpgsql's lexer use palloc not malloc. These changes make plpgsql's
parse-time error reports noticeably nicer (as illustrated by the
regression test changes), and will also simplify the planned removal
of plpgsql's separate lexer by reducing the impedance mismatch
between what it does and what the core lexer does.

- Fix WHERE CURRENT OF to work as designed within plpgsql. The
argument can be the name of a plpgsql cursor variable, which
formerly was converted to $N before the core parser saw it, but
that's no longer the case. Deal with plain name references to
plpgsql variables, and add a regression test case that exposes the
failure.

Andrew Dunstan committed:

- Keep track of language's trusted flag in InlineCodeBlock. Needed to
support DO blocks for languages that have both trusted and untrusted
variants.

== Abgelehnte Patches (bis jetzt) ==

No one was disappointed this week :-)

== Eingesandte Patches ==

Josh Tolley and Andrew Dunstan make call-and-response patches to allow
PL/Perl[U] to have in-line (DO) functions.

Pavel Stehule sent in two revisions of a patch to make it possible to
store the typemods for function parameters, both input and output.

Peter Eisentraut sent in a patch to support arrays in PL/PythonU as
both input and output parameters.

John Naylor sent in a WIP patch to move the current BKI system to one
where one set of files drives the creation of both the bootstrap files
and some hard-coded strings in header files from YAML formatted
descriptions of the system catalogs.

ITAGAKI Takahiro sent in another WIP patch to do partitioning range
and list partitioning directly in SQL.

KaiGai Kohei sent in a patch to disallow renaming a column inherited
from multiple parents.

Alvaro Herrera sent in a WIP patch to fix a corner case where VACUUM
and TRUNCATE don't work together correctly.

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

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

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