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Wöchentlicher PostgreSQL Newsletter - 03. Augus 2008


Der Originalartikel befindet sich unter:
http://people.planetpostgresql.org/dfetter/


== Wöchentlicher PostgreSQL Newsletter - 03. Augus 2008 ==

Wenn du das liest, ist das Juli Commitfest bereits geschlossen. Viele
neue Features wurden hinzugefügt. Im September Commitfest kannst du
nach Common Table Expressions und Windowing Functions Ausschau halten.

== PostgreSQL Produkt Neuigkeiten ==

Npgsql2 RC1 erschienen.
http://www.npgsql.org

pgbouncer 1.2.1 erschienen.
http://pgfoundry.org/projects/pgbouncer/

== PostgreSQL Lokal ==

pgDay San Francisco wird am 5. August stattfinden. Programm:
http://pugs.postgresql.org/node/447
Anmeldung hier:
http://www.linuxworldexpo.com/live/12/ehall//SN460564

Die Prato Linux User Group wird PostgreSQL Vorträge im September
halten. Der Zeitplan in italienisch:
http://www.prato.linux.it/serate_a_tema_2008

Sponsere den Europäischen PostgreSQL Tag!
http://www.pgday.org/en/sponsors/campaign

Der Call for Papers für den Europäischen PostgreSQL Tag hat begonnen.
http://www.pgday.org/en/call4papers

PGCon Brazil 2008 wird vom 26.-27. September auf dem Unicamp in
Campinas stattfinden.
http://pgcon.postgresql.org.br/index.en.html

PgDay.fr wird am 4. Oktober in Toulouse. Der Call for Papers ist
eröffnet:
http://www.postgresqlfr.org/?q=node/1686
Anmeldung hier:
http://www.pgday.fr/doku.php/inscription

PGDay.(IT|EU) 2008 wird am 17. und 18. Oktober in Prato stattfinden.
http://www.pgday.org/it/

== PostgreSQL in den News ==

Planet PostgreSQL: http://www.planetpostgresql.org/

General Bits, Archive und gelegentliche News Artikel:
http://www.varlena.com/GeneralBits/

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 ==

Tom Lane committed:

- Update 8.1 and 8.0 plpython to work with Python 2.5. This backports
several fixes made during the 8.2 development cycle, but not
backported at the time for lack of confidence in the new coding. I
didn't touch 7.4 because it has more problems than this: the
configure probe for Python fails.

- Add a new, improved version of citext as a contrib module. David E.
Wheeler.

- Replace the hard-wired type knowledge in TypeCategory() and
IsPreferredType() with system catalog lookups, as was foreseen to be
necessary almost since their creation. Instead put the information
into two new pg_type columns, typcategory and typispreferred. Add
support for setting these when creating a user-defined base type.
The category column is just a "char" (i.e. a poor man's enum),
allowing a crude form of user extensibility of the category list:
just use an otherwise-unused character. This seems sufficient for
foreseen uses, but we could upgrade to having an actual category
catalog someday, if there proves to be a huge demand for custom type
categories. In this patch I have attempted to hew exactly to the
behavior of the previous hardwired logic, except for introducing new
type categories for arrays, composites, and enums. In particular
the default preferred state for user-defined types remains TRUE.
That seems worth revisiting, but it should be done as a separate
patch from introducing the infrastructure. Likewise, any adjustment
of the standard set of categories should be done separately.

- Adjust citext to make use of the new ability to declare its type
category: by putting it into the standard string category, we cause
casts from citext to text to be recognized as "preferred" casts.
This eliminates the need for creation of alias functions and
operators that only serve to prevent ambiguous-function errors; get
rid of the ones that were in the original commit.

- Flip the default typispreferred setting from true to false. This
affects only type categories in which the previous coding made
every type preferred; so there is no change in effective behavior,
because the function resolution rules only do something different
when faced with a choice between preferred and non-preferred types
in the same category. It just seems safer and less surprising to
have CREATE TYPE default to non-preferred status ...

- Allow I/O conversion casts to be applied to or from any type that is
a member of the STRING type category, thereby opening up the
mechanism for user-defined types. This is mainly for the benefit of
citext, though; there aren't likely to be a lot of types that are
all general-purpose character strings. Per discussion with David
Wheeler.

- Require superuser privilege to create base types (but not
composites, enums, or domains). This was already effectively
required because you had to own the I/O functions, and the I/O
functions pretty much have to be written in C since we don't let PL
functions take or return cstring. But given the possible security
consequences of a malicious type definition, it seems prudent to
enforce superuser requirement directly. Per recent discussion.

- Fix parser so that we don't modify the user-written ORDER BY list in
order to represent DISTINCT or DISTINCT ON. This gets rid of a
longstanding annoyance that a view or rule using SELECT DISTINCT
will be dumped out with an overspecified ORDER BY list, and is one
small step along the way to decoupling DISTINCT and ORDER BY enough
so that hash-based implementation of DISTINCT will be possible. In
passing, improve transformDistinctClause so that it doesn't reject
duplicate DISTINCT ON items, as was reported by Steve Midgley a
couple weeks ago.

- Rearrange the querytree representation of ORDER BY/GROUP BY/DISTINCT
items as per my recent proposal: 1. Fold SortClause and GroupClause
into a single node type SortGroupClause. We were already relying on
them to be struct-equivalent, so using two node tags wasn't
accomplishing much except to get in the way of comparing items with
equal(). 2. Add an "eqop" field to SortGroupClause to carry the
associated equality operator. This is cheap for the parser to get
at the same time it's looking up the sort operator, and storing it
eliminates the need for repeated not-so-cheap lookups during
planning. In future this will also let us represent GROUP/DISTINCT
operations on datatypes that have hash opclasses but no btree
opclasses (ie, they have equality but no natural sort order). The
previous representation simply didn't work for that, since its only
indicator of comparison semantics was a sort operator. 3. Add a
hasDistinctOn boolean to struct Query to explicitly record whether
the distinctClause came from DISTINCT or DISTINCT ON. This allows
removing some complicated and not 100% bulletproof code that
attempted to figure that out from the distinctClause alone. This
patch doesn't in itself create any new capability, but it's
necessary infrastructure for future attempts to use hash-based
grouping for DISTINCT and UNION/INTERSECT/EXCEPT.

- In pgsql/src/test/regress/pg_regress.c, fix copy-and-pasteo that's
causing pg_regress to lie about which file it can't read when the
--temp-config argument is bad. Noted while wondering why buildfarm
member dungbeetle is failing ... this isn't why, but it is why the
error report isn't very helpful ...

- In pgsql/src/backend/catalog/pg_type.c, tighten up the sanity checks
in TypeCreate(): pass-by-value types must have a size that is one of
the supported values, not just anything <= sizeof(Datum).
Cross-check the alignment specification against size as well.

- Make GROUP BY work properly for datatypes that only support hashing
and not sorting. The infrastructure for this was all in place
already; it's only necessary to fix the planner to not assume that
sorting is always an available option.

Magnus Hagander committed:

- In pgsql/doc/src/sgml/install-win32.sgml, document which versions of
ActivePerl and ActiveTcl are required for building on MSVC, and that
the free distribution is enough (no need for the enterprise
version). Per gripe from Martin Zaun.

- In pgsql/doc/src/sgml/install-win32.sgml, clean up reference to
config.pl so it makes sense not only in SGML source but in the
actual web/pdf viewer...

- Move ident authentication code into auth.c along with the other
authenciation routines, leaving hba.c to deal only with processing
the HBA specific files.

- In pgsql/src/backend/libpq/auth.c, rearrange the code in auth.c so
that all functions for a single authentication method is grouped
together in a reasonably similar way, keeping the "global shared
functions" together in their own section as well. Makes it a lot
easier to find your way around the code.

Bruce Momjian committed:

- Add URL for TODO: "Consider decreasing the I/O caused by updating
tuple hint bits."

Alvaro Herrera committed:

- Add a few more DTrace probes to the backend. Robert Lor.

- Cope with Tcl versions that do not create a tclsh symlink to the
version- numbered program. Per persistent buildfarm failures. Tom
Lane.

== Abgelehnte Patches (bis jetzt) ==

No one was disappointed this week :-)

== Eingesandte Patches ==

Tatsuo Ishii sent in another revision of Yoshiuki Asaba's CTE patch.

Hitoshi Harada sent in another revision of his windowing functions
patch.

Jan Urbanski sent in two more revisions of his patch to add
selectivity functions for text search types.

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

Abhijit Menon-Sen sent in two more revisions of his \ef (edit
function) patch for psql along with a patch to add
pg_get_functiondef() as an SQL-callable function.

Robert Lor sent in two more revisions of his DTrace probes patch.

ITAGAKI Takahiro sent in a patch to add STORAGE and reloptions to
CREATE TABLE ... LIKE.

Alvaro Herrera sent in two updates to Robert Lor's DTrace probes
patch.

ITAGAKI Takahiro sent in a patch to use NDirectFileRead and
NDirectFileWrite statistics counters for counting reads and writes in
BufFile.

Heikki Linnakangas sent in new revisions of his Relation Forks and FSM
rewrite patches, the latter depending on the former.

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