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== Postgres Weekly News - 22 giugno 2008 ==

From: rotellaro(at)gmail(dot)com
To: pgsql-it-generale <pgsql-it-generale(at)postgresql(dot)org>
Subject: == Postgres Weekly News - 22 giugno 2008 ==
Date: 2008-06-24 14:31:08
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Lists: pgsql-it-generale
Nuovo Sondaggio: Quale TODO vi piace di più?

== Offerte di lavoro legate a PostgreSQL per il mese di Giugno ==

== PostgreSQL news locali ==

Il primo meeting del TorontoPUG ci sarà il 23 giugno al Rhino.

L'Oklahoma PUG terrà il suo primo meeting il 23 giugno dalle 19:00
alle 21:00 presso Coach's, Norman, OK.

Il meeting di preparazione al PgDay italiano ci sarà mercoledi 25
giugno alle ore 2130 CET via IRC.

Il pgDay di Portland ci sarà il 20 luglio. Poco prima di OSCON.

Il PGCon Brasile 2008 ci sara' il 26 e 27 settembre 2008 a Unicamp, Campinas.

Il PGDay.IT 2008 ci sarà il 17 e 18 ottobre a Prato.

== News su PostgreSQL ==

Planet PostgreSQL:

General Bits, archivi e nuovi articoli occasionali:

PostgreSQL Weekly News è stato spedito questa settimana grazie a David
Fetter e Josh Berkus.

Per segnalare news e annunci invia un email in inglese entro le ore 15,
fuso orario della costa orientale degli U.S.A, di domenica.

Per segnalazioni in inglese david(at)fetter(dot)org, per segnalazioni in
Tedesco pwn(at)pgug(dot)de, per segnalazioni in italiano pwn(at)itpug(dot)org

== Patch applicate ==
Tom Lane committed:

- Clean up a number of bogosities around pltcl's handling of the Tcl
 "result": 1. Directly reading interp->result is deprecated in Tcl
 8.0 and later; you're supposed to use Tcl_GetStringResult.  This
 code finally broke with Tcl 8.5, because Tcl_GetVar can now have
 side-effects on interp->result even though it preserves the logical
 state of the result.  (There's arguably a Tcl issue here, because
 Tcl_GetVar could invalidate the pointer result of a just-preceding
 Tcl_GetStringResult, but I doubt the Tcl guys will see it as a bug.)
 2. We were being sloppy about the encoding of the result: some
 places would push database-encoding data into the Tcl result, which
 should not happen, and we were assuming that any error result coming
 back from Tcl was in the database encoding, which is not a good
 assumption.  3. There were a lot of calls of Tcl_SetResult that
 uselessly specified TCL_VOLATILE for constant strings.  This is only
 a minor performance issue, but I fixed it in passing since I had to
 look at all the calls anyway.  #2 is a live bug regardless of which
 Tcl version you are interested in, so back-patch even to branches
 that are unlikely to be used with Tcl 8.5.  I went back as far as
 8.0, which is as far as the patch applied easily; 7.4 was using a
 different error processing scheme that has got its own problems :-(

- In pgsql/src/backend/optimizer/plan/setrefs.c, fix the code that
 adds regclass constants to a plan's list of relation OIDs that it
 depends on for replan-forcing purposes.  We need to consider plain
 OID constants too, because eval_const_expressions folds a
 RelabelType atop a Const to just a Const.  This change could result
 in OID values that aren't really for tables getting added to the
 dependency list, but the worst-case consequence would be occasional
 useless replans.  Per report from Gabriele Messineo.

- Clean up some problems with redundant cross-type arithmetic
 operators.  Add int2-and-int8 implementations of the basic
 arithmetic operators +, -, *, /.  This doesn't really add any new
 functionality, but it avoids "operator is not unique" failures that
 formerly occurred in these cases because the parser couldn't decide
 whether to promote the int2 to int4 or int8.  We could alternatively
 have removed the existing cross-type operators, but experimentation
 shows that the cost of an additional type coercion expression node
 is noticeable compared to such cheap operators; so let's not give up
 any performance here.  On the other hand, I removed the
 int2-and-int4 modulo (%) operators since they didn't seem as
 important from a performance standpoint.  Per a complaint last
 January from ykhuang.

- In pgsql/src/backend/storage/ipc/sinvaladt.c, remove freeBackends
 counter from the sinval shared memory area.  We used to use it to
 help enforce superuser_reserved_backends, but since 8.1 it's just
 been dead weight.

- Improve error reporting for problems in text search configuration
 files by installing an error context subroutine that will provide
 the file name and line number for all errors detected while reading
 a config file.  Some of the reader routines were already doing that
 in an ad-hoc way for errors detected directly in the reader, but it
 didn't help for problems detected in subroutines, such as encoding
 violations.  Back-patch to 8.3 because 8.3 is where people will be
 trying to debug configuration files.

- In pgsql/src/backend/utils/mb/mbutils.c, fix compiler warning
 introduced by recent patch.  Tsk tsk.

- Fix a few places that were non-multibyte-safe in tsearch
 configuration file parsing.  Per bug #4253 from Giorgio Valoti.

- Rewrite the sinval messaging mechanism to reduce contention and
 avoid unnecessary cache resets.  The major changes are: 1.  When the
 queue overflows, we only issue a cache reset to the specific backend
 or backends that still haven't read the oldest message, rather than
 resetting everyone as in the original coding.  2.  When we observe
 backend(s) falling well behind, we signal SIGUSR1 to only one
 backend, the one that is furthest behind and doesn't already have a
 signal outstanding for it.  When it finishes catching up, it will in
 turn signal SIGUSR1 to the next-furthest-back guy, if there is one
 that is far enough behind to justify a signal.  The
 PMSIGNAL_WAKEN_CHILDREN mechanism is removed.  3.  We don't attempt
 to clean out dead messages after every message-receipt operation;
 rather, we do it on the insertion side, and only when the queue
 fullness passes certain thresholds.  4.  Split SInvalLock into
 SInvalReadLock and SInvalWriteLock so that readers don't block
 writers nor vice versa (except during the infrequent queue cleanout
 operations).  5.  Transfer multiple sinval messages for each
 acquisition of a read or write lock.

- In pgsql/src/backend/storage/ipc/sinvaladt.c, seems I was too
 optimistic in supposing that sinval's maxMsgNum could be read and
 written without a lock.  The value itself is atomic, sure, but on
 processors with weak memory ordering it's possible for a reader to
 see the value change before it sees the associated message written
 into the buffer array.  Fix by introducing a spinlock that's used
 just to read and write maxMsgNum.  (We could do this with less
 overhead if we recognized a concept of "memory access barrier"; is
 it worth introducing such a thing?  At the moment probably not --- I
 can't measure any clear slowdown from adding the spinlock, so this
 solution is probably fine.)  Per buildfarm results.

Bruce Momjian committed:

- Move USE_WIDE_UPPER_LOWER define to c.h, and remove TS_USE_WIDE and
 use USE_WIDE_UPPER_LOWER instead.

- In pgsql/src/backend/utils/mb/README, add URL for introduction to
 multibyte programming in C.

- Move wchar2char() and char2wchar() from tsearch into /mb to be
 easier to use for other modules;  also move pnstrdup().  Clean up
 code slightly.

- Add URL for TODO: "Allow pg_hba.conf to specify host names along
 with IP addresses."

Neil Conway committed:

- In pgsql/doc/src/sgml/monitoring.sgml, fix a few typos in the DTrace
 docs.  Patch from Euler Taveira de Oliveira, along with an
 additional typo I noticed along the way.

Alvaro Herrera committed:

- Improve our #include situation by moving pointer types away from the
 corresponding struct definitions.  This allows other headers to
 avoid including certain highly-loaded headers such as rel.h and
 relscan.h, instead using just relcache.h, heapam.h or genam.h, which
 are more lightweight and thus cause less unnecessary dependencies.

== Patch rigettate (per ora) ==
Nessuno è stato scontentato questa settimana ;)

== Patch in attesa ==
Zoltan Boszormenyi sent in another revision of his POSIX fadvise

Simon Riggs sent in a patch to improve performance via hint bits for
write I/O.

(all opinions expressed are my own)
Federico Campoli
PostgreSQL Consulting -> PGHost

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Subject: Re: Float in java, come in Postgres?
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Subject: Float in java, come in Postgres?

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