== Notiziario settimanale PostgreSQL - 7 giugno 2009 ==

== Notiziario settimanale PostgreSQL - 7 giugno 2009 ==

(Traduzione parziale in lingua italiana delle PostgreSQL Weekly News a
cura di Gianni Ciolli <gianni(dot)ciolli(at)2ndquadrant(dot)it>)

Il CfP per PGCon Brazil è aperto!
http://pgcon.postgresql.org.br/2009/chamadas.en.php

ITPUG sarà alla Conferenza Italiana per il Software Libero (ConfSL)
che si terrà a Bologna il 12 e 13 giugno. Gabriele Bartolini
presenterà "Studenti e Open-source: il caso di PostgreSQL" alle 10:35
di sabato 13 giugno.
http://www.confsl.org/

== Novità sul prodotto PostgreSQL ==

Rilasciato pgtheme, sviluppato specificamente per il sistema di temi
di Drupal 6.x .
http://drupal.org/project/pgtheme

== La novità della settimana di PostgreSQL 8.4 ==

quote_nullable: come quote_literal, eccetto che restituisce la stringa
NULL se l'argomento è null.

== Il suggerimento della settimana ==

Il modulo contrib "ltree" è una implementazione di alberi con
etichette, dotata di indici; può essere usato ad esempio per
rappresentare nel vostro database un filesystem, o una gerarchia di
tipo simile.

== Notizie locali su PostgreSQL ==

Il pgday di San Jose (USA) si terrà domenica 19 luglio 2009, dando il
via ad OSCON. Inviate la vostra proposta entro l'8 giugno 2009 a
conference-sf-speakers AT pgfoundry DOT org, e scoprirete entro il 20
giugno 2009 se è stata accettata.
http://www.postgresql.org/about/news.1082

Il 23 e 24 ottobre 2009 si svolgerà PGCon Brazil, presso Unicamp,
nella città di Campinas, stato di San Paolo.

Il PGDay.EU 2009 si terrà a Telecom ParisTech in Parigi nei giorni 6 e
7 novembre 2009.
http://www.pgday.eu/

Gli organizzatori della conferenza per il decimo anniversario di JPUG
stanno accettando proposte. La conferenza si terrà i giorni 20 e 21
novembre 2009 a Tokio.
http://archives.postgresql.org/pgsql-announce/2009-05/msg00018.php

== Rassegna stampa su PostgreSQL ==

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

Questo notiziario settimanale PostgreSQL è stato realizzato da David
Fetter e Josh Berkus; traduzione parziale in lingua italiana a cura di
Gianni Ciolli.

Notizie o annunci destinati a questo notiziario dovranno pervenire
entro la mezzanotte di domenica (le 15 nel fuso orario della
California). I comunicati in lingua italiana dovranno essere inviati a
pwn(at)itpug(dot)org; per le lingue inglese o tedesca, si scriva
rispettivamente a david(at)fetter(dot)org o a pwd(at)pgug(dot)de(dot)

== Patch applicate ==

Tom Lane committed:

- Fix DecodeInterval to report an error for multiple occurrences of
DAY, WEEK, YEAR, DECADE, CENTURY, or MILLENIUM fields, just as it
always has done for other types of fields. The previous behavior
seems to have been a hack to avoid defining bit-positions for all
these field types in DTK_M() masks, rather than something that was
really considered to be desired behavior. But there is room in the
masks for these, and we really need to tighten up at least the
behavior of DAY and YEAR fields to avoid unexpected behavior
associated with the 8.4 changes to interpret ambiguous fields based
on the interval qualifier (typmod) value. Per my example and
proposed patch.

- Change AdjustIntervalForTypmod to not discard higher-order field
values on the grounds that they don't fit into the specified
interval qualifier (typmod). This behavior, while of long standing,
is clearly wrong per spec --- for example the value INTERVAL '999'
SECOND means 999 seconds and should not be reduced to less than 60
seconds. In some cases there could be grounds to raise an error if
higher-order field values are not given as zero; for example '1 year
1 month'::INTERVAL MONTH should arguably be taken as an error rather
than equivalent to 13 months. However our internal representation
doesn't allow us to do that in a fashion that would consistently
reject all and only the cases that a strict reading of the spec
would suggest. Also, seeing that for example INTERVAL '13' MONTH
will print out as '1 year 1 mon', we have to be careful not to
create a situation where valid data will fail to dump and reload.
The present patch therefore takes the attitude of not throwing an
error in any such case. We might want to revisit that in future but
it would take more redesign than seems prudent in late beta. Per a
complaint from Sebastien Flaesch and subsequent discussion. While
at other times we might have just postponed such an issue to the
next development cycle, 8.4 already has changed the parsing of
interval literals quite a bit in an effort to accept all
spec-compliant cases correctly. This seems like a change that
should be part of that rather than coming along later.

- In pgsql/doc/src/sgml/config.sgml, Remove the old advice to keep
from_collapse_limit less than geqo_threshold, instead just pointing
out that a larger value may trigger use of GEQO. Per Robert Haas.
In passing, do a bit of wordsmithing on the Genetic Query Optimizer
section.

- In pgsql/src/backend/commands/copy.c, improve comment about 'if (1)'
hack in copy.c macros.

- In pgsql/src/bin/initdb/initdb.c, change rather bizarre code
ordering in get_id(). This isn't strictly cosmetic --- I'm
wondering if geteuid could have side effects on errno, thus possibly
resulting in a misleading error message after failure of getpwuid.

- In pgsql/src/backend/tsearch/ts_selfuncs.c, fix tsquerysel() to not
fail on an empty TSQuery. Per report from Tatsuo Ishii.

- Clean up ecpg's use of mmerror(): const-ify the format argument, add
an __attribute__() marker so that gcc can validate the format string
against the actual arguments, get rid of overcomplicated and unsafe
usage in base_yyerror().

- Improve the recently-added support for properly pluralized error
messages by extending the ereport() API to cater for pluralization
directly. This is better than the original method of calling
ngettext outside the elog.c code because (1) it avoids double
translation, which wastes cycles and in the worst case could give a
wrong result; and (2) it avoids having to use a different coding
method in PL code than in the core backend. The client-side uses of
ngettext are not touched since neither of these concerns is very
pressing in the client environment. Per my proposal of yesterday.

- Remove a couple of debugging messages that have been #ifdef'd out
for ages. Seems silly to ask translators to expend work on these,
especially in pluralized variants.

- Trivial code style cleanup around a couple of ngettext calls.

- GIN's ItemPointerIsMin, ItemPointerIsMax, and ItemPointerIsLossyPage
macros should use GinItemPointerGetBlockNumber/
GinItemPointerGetOffsetNumber, not ItemPointerGetBlockNumber/
ItemPointerGetOffsetNumber, because the latter will Assert() on
ip_posid == 0, ie a "Min" pointer. (Thus, ItemPointerIsMin has
never worked at all, but it seems unused at present.) I'm not
certain that the case can occur in normal functioning, but it's
blowing up on me while investigating Tatsuo-san's data corruption
problem. In any case it seems like a problem waiting to bite
someone. Back-patch just in case this really is a problem for
somebody in the field.

- Fix a serious bug introduced into GIN in 8.4: now that
MergeItemPointers() is supposed to remove duplicate heap TIDs, we
have to be sure to reduce the tuple size and posting-item count
accordingly in addItemPointersToTuple(). Failing to do so resulted
in the effective injection of garbage TIDs into the index contents,
ie, whatever happened to be in the memory palloc'd for the new
tuple. I'm not sure that this fully explains the index corruption
reported by Tatsuo Ishii, but the test case I'm using no longer
fails.

- In pgsql/src/pl/plperl/plperl.c, move variable declaration to avoid
'unused variable' warning when the ifdef doesn't trigger. Not worth
back-patching. Per buildfarm reports.

- Improve the IndexVacuumInfo/IndexBulkDeleteResult API to allow
somewhat sane behavior in cases where we don't know the heap tuple
count accurately; in particular partial vacuum, but this also makes
the API a bit more useful for ANALYZE. This patch adds
"estimated_count" flags to both structs so that an approximate count
can be flagged as such, and adjusts the logic so that approximate
counts are not used for updating pg_class.reltuples. This fixes my
previous complaint that VACUUM was putting ridiculous values into
pg_class.reltuples for indexes. The actual impact of that bug is
limited, because the planner only pays attention to reltuples for an
index if the index is partial; which probably explains why beta
testers hadn't noticed a degradation in plan quality from it. But
it needs to be fixed. The whole thing is a bit messy and should be
redesigned in future, because reltuples now has the potential to
drift quite far away from reality when a long period elapses with no
non-partial vacuums. But this is as good as it's going to get for
8.4.

- Revert my patch of 2009-04-04 that removed contrib/intarray's
definitions of the <@ and @> operators. These are not in fact
equivalent to the built-in anyarray operators of the same names,
because they have different behavior for empty arrays, namely they
don't think empty arrays are contained in anything. That is
mathematically wrong, no doubt, but until we can persuade GIN
indexes to implement the mathematical definition we should probably
not change this. Another reason for not changing it now is that we
can't yet ensure the opclasses will be updated correctly in a
dump-and-reload upgrade. Per recent discussions.

Joe Conway committed:

- In pgsql/contrib/dblink/dblink.c, fix dblink_get_result() as
reported by Oleksiy Shchukin. Refactor a bit while we're at it per
request by Tom Lane. Specifically, don't try to perform
dblink_send_query() via dblink_record_internal() -- it was
inappropriate and ugly.

- Add support for using SQL/MED compliant FOREIGN DATA WRAPPER,
SERVER, and USER MAPPING as method to supply dblink connect
parameters. Per mailing list and PGCon discussions.

Heikki Linnakangas committed:

- In pgsql/src/backend/access/transam/xlog.c, only recycle normal
files in pg_xlog as WAL segments. pg_standby creates symbolic links
with the -l option, and as Fujii Masao pointed out we ended up
overwriting files in the archive directory before this patch. Patch
by Aidan Van Dyk, Fujii Masao and me.

Bruce Momjian committed:

- In pgsql/doc/src/sgml/config.sgml, add example of how to generate
the session identifier from pg_stat_activity.

- In pgsql/src/backend/commands/copy.c, add comment about why
"((void) 0)" is used in copy macros.

- Wording improvement for recent sesssion identifier SQL query.

- In pgsql/doc/src/sgml/config.sgml, wording improvement for recent
sesssion identifier SQL query.

- In pgsql/doc/src/sgml/backup.sgml, remove sleep() from backup script
example; not needed anymore. Fujii Masao.

Andrew Dunstan committed:

- Initialise perl library as documented in perl API. Backpatch to
release 7.4.

- Search for versioned perl library instead of using hardcoded name on
Windows. Backpatch to release 8.3

- Adjust recent PERL_SYS_INIT3 call to avoid platforms where it might
fail, and to remove compilation warning. Backpatch the release 7.4.

== Patch rifiutate (per adesso) ==

No one was disappointed this week :-)