Notiziario settimanale PostgreSQL – 5 aprile 2009

(Traduzione parziale in lingua italiana delle PostgreSQL Weekly News a cura di Gianni Ciolli gianni.ciolli@2ndquadrant.it)

È aperta la registrazione per la pgCon in Ottawa: http://www.pgcon.org/2009/registration.php

È aperta la registrazione per OSCON. Ci sarà un pgDay la domenica prima di OSCON: https://en.oreilly.com/oscon2009/public/register

Il PgDay di Florianopolis (Brasile) sarà il 22 maggio. Mettetevi in contatto con Dickson S. Guedes (guedes AT guedesoft DOT net) per partecipare o inviare un lavoro. http://www.postgresql.org.br/eventos/pgday/sc

Novità sul prodotto PostgreSQL

Rilasciate le versioni 3.0.7 e 3.1.0 di Archiveopteryx, un sistema di gestione della posta elettronica basato su PostgreSQL. http://www.archiveopteryx.org/3.0.7 http://www.archiveopteryx.org/3.1.0

Rilasciata la versione 0.09 di PGORM, un sistema di mappatura relazionale a oggetti .NET per PostgreSQL. http://pgorm.googlecode.com

Rilasciata la versione 2.5.1 di PostgreDAC. http://microolap.com/products/connectivity/postgresdac/download/

La novità della settimana di PostgreSQL 8.4

• CIText: David Wheeler ha aggiunto un nuovo modulo contrib che implementa un tipo di data Case Insensitive Text pienamente funzionale.

Il suggerimento della settimana

• h in psql fornisce la documentazione completa di una gran parte di comandi SQL.

Offerte di lavoro su PostgreSQL per aprile 2009

http://archives.postgresql.org/pgsql-jobs/2009-04/threads.php

Notizie locali su PostgreSQL

Kevin Kempter parlerà di backup e recovery al primo incontro del PUG di Denver (USA) in data 8 aprile 2009. http://www.diapug.org/Meeting.html

Il PgDay Brasilia sarà il 17 aprile. Per partecipare mettersi in contatto con fernando.ike AT gmail DOT com oppure eduardo DOT santos AT planejamento DOT gov DOT br.

La Percona Performance Conference si svolgerà presso il Santa Clara Convention Center, Santa Clara, California, USA http://conferences.percona.com/

Aperto il CfP per il PgDay São Paulo, che si terrà il 24 aprile. Per partecipare mettersi in contatto con marins DOT consultoria AT gmail DOT com oppure marcelojscosta AT gmail DOT com.

La PostgreSQL Conference U. S. organizzerà un PgDay nell’ambito della LinuxFest Northwest (25, 26 aprile). Informazioni su come proporre una comunicazione sono disponibili sul sito http://www.postgresqlconference.org/

Ci saranno anche dei PgDay il 29 aprile a Porto Velho, RO, e il 30 in Ji-Parana, RO. Per partecipare mettersi in contatto con Luis Fernando Bueno: proflfbueno AT gmail DOT com.

Michael Renner farà un workshop sulla replica con PostgreSQL a Netways OSDC 2009 il 29 e 30 aprile a Norimberga, in Germania. http://www.netways.de/english/osdc/y2009/programm/w/michael_renner_postgresql_repliziert_ein_ueberblick/

Nei giorni 21 e 22 maggio 2009 all’università di Ottawa, in Canada, si terrà PGCon 2009. Nei due giorni precedenti si terranno dei tutorials. http://www.pgcon.org/2009/

Segnatevi la data: pgDay San Jose (USA). Domenica 19 luglio subito prima di OSCON. Saranno presto annunciate ulteriori informazioni! (incluso il call for papers)

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

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@itpug.org; per le lingue inglese o tedesca, si scriva rispettivamente a david@fetter.org o a pwd@pgug.de.

Patch Applicate

Tom Lane committed:

• Fix an oversight in the support for storing/retrieving "minimal tuples" in TupleTableSlots. We have functions for retrieving a minimal tuple from a slot after storing a regular tuple in it, or vice versa; but these were implemented by converting the internal storage from one format to the other. The problem with that is it invalidates any pass-by-reference Datums that were already fetched from the slot, since they’ll be pointing into the just-freed version of the tuple. The known problem cases involve fetching both a whole-row variable and a pass-by-reference value from a slot that is fed from a tuplestore or tuplesort object. The added regression tests illustrate some simple cases, but there may be other failure scenarios traceable to the same bug. Note that the added tests probably only fail on unpatched code if it’s built with –enable-cassert; otherwise the bug leads to fetching from freed memory, which will not have been overwritten without additional conditions. Fix by allowing a slot to contain both formats simultaneously; which turns out not to complicate the logic much at all, if anything it seems less contorted than before. Back-patch to 8.2, where minimal tuples were introduced.

• In pgsql/src/backend/optimizer/plan/planner.c, fix window function plan generation to cope with volatile sort expressions. (Not clear how useful these really are, but failing is no good…) Per report from David Fetter and Robert Treat.

• Add PQinitOpenSSL() function to support applications that use libcrypto but not OpenSSL (or perhaps vice versa, if that’s possible). Andrew Chernow, with minor editorialization by me.

• Add a "relistemp" boolean column to pg_class, which is true for temporary relations (including a temp table’s indexes and toast table/index), and false for normal relations. For ease of checking, this commit just adds the column and fills it correctly — revising the relation access machinery to use it will come separately.

• Modify the relcache to record the temp status of both local and nonlocal temp relations; this is no more expensive than before, now that we have pg_class.relistemp. Insert tests into bufmgr.c to prevent attempting to fetch pages from nonlocal temp relations. This provides a low-level defense against bugs-of-omission allowing temp pages to be loaded into shared buffers, as in the contrib/pgstattuple problem reported by Stuart Bishop. While at it, tweak a bunch of places to use new relcache tests (instead of expensive probes into pg_namespace) to detect local or nonlocal temp tables.

• Fix contrib/pgstattuple and contrib/pageinspect to prevent attempts to read temporary tables of other sessions; that is unsafe because of the way our buffer management works. Per report from Stuart Bishop. This is redundant with the bufmgr.c checks in HEAD, but not at all redundant in the back branches.

• Remove last references to the crypt auth method, per Andreas ‘ads’ Scherbaum.

• In pgsql/doc/src/sgml/func.sgml, index some array functions, per Mario Splivalo.

• In pgsql/src/bin/pg_dump/pg_dump.c, improve pg_dump’s query for retrieving BLOB comments to be more efficient when there are many blobs and not so many comments. Tamas Vincze.

• In pgsql/src/pl/plpgsql/src/pl_exec.c, plpgsql’s exec_simple_cast_value() mistakenly supposed that it could bypass casting effort whenever the input value was NULL. However this prevents application of not-null domain constraints in the cases that use this function, as illustrated in bug #4741. Since this function isn’t meant for use in performance-critical paths anyway, this certainly seems like another case of "premature optimization is the root of all evil". Back-patch as far as 8.2; older versions made no effort to enforce domain constraints here anyway.

• In pgsql/src/backend/utils/misc/guc.c, fix GUC’s reports of assign_hook failure to always include the parameter value we failed to assign, even in "can’t happen" cases. Motivated by wondering what’s going on in a recent trouble report where "failed to commit" did happen.

• Fix SetClientEncoding() to maintain a cache of previously selected encoding conversion functions. This allows transaction rollback to revert to a previous client_encoding setting without doing fresh catalog lookups. I believe that this explains and fixes the recent report of "failed to commit client_encoding" failures. This bug is present in 8.3.x, but it doesn’t seem prudent to back-patch the fix, at least not till it’s had some time for field testing in HEAD. In passing, remove SetDefaultClientEncoding(), which was used nowhere.

• In pgsql/src/pl/plpgsql/src/pl_exec.c, minor code beautification/consolidation.

• Refactor ExecProject and associated routines so that fast-path code is used for simple Var targetlist entries all the time, even when there are other entries that are not simple Vars. Also, ensure that we prefetch attributes (with slot_getsomeattrs) for all Vars in the targetlist, even those buried within expressions. In combination these changes seem to significantly reduce the runtime for cases where tlists are mostly but not exclusively Vars. Per my proposal of yesterday.

• Defend against possible crash if a plpython function does not specify names for its arguments. Also add a regression test, since someone apparently changed every single plpython test case to use only named parameters; else we’d have noticed this sooner. Euler Taveira de Oliveira, per a report from Alvaro Herrera.

• In pgsql/src/backend/storage/buffer/bufmgr.c, add a comment documenting the question of whether PrefetchBuffer should try to protect an already-existing buffer from being evicted. This was left as an open issue when the posix_fadvise patch was committed. I’m not sure there’s any evidence to justify more work in this area, but we should have some record about it in the source code.

• In pgsql/src/port/path.c, use (unsigned char) cast in argument of pg_tolower(). Maybe it works on Windows without that, but we shouldn’t put bad examples where people might copy them. Also, reformat slightly to improve the odds that pgindent won’t go nuts on this.

• In pgsql/src/bin/psql/help.c, add missing help output for ef option. Andrew (RhodiumToad) Gierth.

• In pgsql/doc/src/sgml/ref/psql-ref.sgml, minor wordsmithing on descriptions of some d commands.

• In pgsql/src/bin/psql/describe.c, make dt di and friends more consistent about the treatment of TOAST tables and indexes; to wit, never show either. (You can examine them with plain d if you’re really so inclined.)

• In pgsql/src/bin/psql/describe.c, improve obsolete comment.

• Rewrite interval_hash() so that the hashcodes are equal for values that interval_eq() considers equal. I’m not sure how that fundamental requirement escaped us through multiple revisions of this hash function, but there it is; it’s been wrong since interval_hash was first written for PG 7.1. Per bug #4748 from Roman Kononov. Backpatch to all supported releases. This patch changes the contents of hash indexes for interval columns. That’s no particular problem for PG 8.4, since we’ve broken on-disk compatibility of hash indexes already; but it will require a migration warning note in the next minor releases of all existing branches: "if you have any hash indexes on columns of type interval, REINDEX them after updating".

• A session that does not have any live snapshots does not have to be waited for when we are waiting for old snapshots to go away during a concurrent index build. In particular, this rule lets us avoid waiting for idle-in-transaction sessions. This logic could be improved further if we had some way to wake up when the session we are currently waiting for goes idle-in-transaction. However that would be a significantly more complex/invasive patch, so it’ll have to wait for some other day. Simon Riggs, with some improvements by Tom.

• Remove the recently added node types ReloptElem and OptionDefElem in favor of adding optional namespace and action fields to DefElem. Having three node types that do essentially the same thing bloats the code and leads to errors of confusion, such as in yesterday’s bug report from Khee Chin.

• Make an attempt at fixing our current Solaris 11 breakage: add a configure probe for opterr (exactly like the one for optreset) and have getopt.c define the variables only if configure doesn’t find them in libc.

• In pgsql/src/port/getopt.c, hmm, baiji thinks we need explicit ‘extern’ here.

• Remove contrib/intarray’s definitions of the <@ and @> operators, so that they don’t cause confusion with the built-in anyarray versions of those operators. Adjust the module’s index opclasses to support the built-in operators in place of the private ones. The private implementations are still available under their historical names @ and ~, so no functionality is lost. Some quick testing suggests that they offer no real benefit over the core operators, however. Per a complaint from Rusty Conover.

• In pgsql/src/include/pg_config.h.win32, I had always wondered why pg_config.h.win32 claimed that Windows provides optreset. Current mastodon results prove that in fact it does not; it was only because getopt.c defined the variable anyway that things failed to fall over.

• Remove a boatload of useless definitions of ‘int optreset’. If we are using our own ports of getopt or getopt_long, those will define the variable for themselves; and if not, we don’t need these, because we never touch the variable anyway.

• Change EXPLAIN output so that subplans and initplans (particularly CTEs) are individually labeled, rather than just grouped under an "InitPlan" or "SubPlan" heading. This in turn makes it possible for decompilation of a subplan reference to usefully identify which subplan it’s referencing. I also made InitPlans identify which parameter symbol(s) they compute, so that references to those parameters elsewhere in the plan tree can be connected to the initplan that will be executed. Per a gripe from Robert Haas about EXPLAIN output of a WITH query being inadequate, plus some longstanding pet peeves of my own.

• In pgsql/src/backend/executor/execQual.c, make ExecInitExpr build the list of SubPlans found in a plan tree in order of discovery, rather than reverse order. This doesn’t matter functionally (I suppose the previous coding dates from the time when lcons was markedly cheaper than lappend). However now that EXPLAIN is labeling subplans with IDs that are based on order of creation, this may help produce a slightly less surprising printout.

• Change cardinality() into a C-code function, instead of a SQL-language alias for array_length(v,1). The efficiency gain here is doubtless negligible — what I’m interested in is making sure that if we have second thoughts about the definition, we will not have to force a post-beta initdb to change the implementation.

Alvaro Herrera committed:

• In pgsql/doc/src/sgml/plpython.sgml, update URL to Python bug tracker. Backpatch to 8.3; doesn’t seem worthy of further backpatch.

• Disallow setting fillfactor for TOAST tables. To implement this without almost duplicating the reloption table, treat relopt_kind as a bitmask instead of an integer value. This decreases the range of allowed values, but it’s not clear that there’s need for that much values anyway. This patch also makes heap_reloptions explicitly a no-op for relation kinds other than heap and TOAST tables. Patch by ITAGAKI Takahiro with minor edits from me. (In particular I removed the bit about adding relation kind to an error message, which I intend to commit separately.)

Bruce Momjian committed:

• In pgsql/doc/src/sgml/release.sgml, reorder release note sections.

• In pgsql/doc/src/sgml/release.sgml, more release note wording improvements; section order adjustments.

• In pgsql/doc/src/sgml/release.sgml, more release note adjustments, reordering.

• In pgsql/doc/src/sgml/release.sgml, more release note changes, including a lower level of subsections.

• In pgsql/doc/src/sgml/release.sgml, more new subsections in release notes.

• In pgsql/doc/src/sgml/release.sgml, update release note introductory description.

• In pgsql/doc/src/sgml/release.sgml, remove some "Other" sections in the release notes by putting the items at the top of their sections.

• Change psql da_installare_pandoc display so ‘S’ _or_ a pattern include system objects.

• In pgsql/src/bin/psql/describe.c, do not show information_schema in da_installare_pandoc commands, unless ‘S’ or pattern is specified. Martin Pihlak.

• Add support for additional DTrace probes. Robert Lor.

• Have PL/pgSQL FETCH set DIAGNOSTICS ROW_COUNT. Andrew (RhodiumToad) Gierth.

• In pgsql/src/backend/utils/misc/guc.c, give a better error message when trying to change "effective_io_concurrency" on systems without posix_fadvise().

• Revert DTrace patch from Robert Lor.

• In pgsql/doc/src/sgml/config.sgml, document that Solaris can’t use effective_io_concurrency because of an ineffective posix_fadvise().

Heikki Linnakangas committed:

• In pgsql/src/backend/storage/ipc/procarray.c, fix a rare race condition when commit_siblings > 0 and a transaction commits at the same instant as a new backend is spawned. Since CountActiveBackends() doesn’t hold ProcArrayLock, it needs to be prepared for the case that a pointer at the end of the proc array is still NULL even though numProcs says it should be valid, since it doesn’t hold ProcArrayLock. Backpatch to 8.1. 8.0 and earlier had this right, but it was broken in the split of PGPROC and sinval shared memory arrays. Per report and proposal by Marko Kreen.

• In pgsql/src/backend/utils/adt/pg_locale.c, update comment to reflect that LC_COLLATE and LC_CTYPE are now per-database settings.

Magnus Hagander committed:

• In pgsql/src/bin/initdb/initdb.c, don’t crash initdb when we fail to get the current username. Give an error message and exit instead, like we do elsewhere… Per report from Wez Furlong and Robert Treat.

• In pgsql/src/port/path.c, make directory name comparisons on Win32 case insensitive. This method will not catch all different ways since the locale handling in NTFS doesn’t provide an easy way to do that, but it will hopefully solve the most common cases causing startup problems when the backend is found in the system PATH. Attempts to fix bug #4694.

Teodor Sigaev committed:

• In pgsql/contrib/hstore/hstore_io.c, fix memory allocation for output of hstore type. Per report from Zhang Maosen.

• Fix infinite loop while checking of partial match in pending list. Improve comments. Now GIN-indexable operators should be strict. Per Tom Lane’s questions/suggestions.

Patch rifiutate (per adesso)

La patch alla documentazione di Hitoshi Harada che cambiava HeapTupleSatisfiesNow in HeapTupleSatisfiesVisibility nel file doc/src/sgml/pgstattuple.sgml.

Patch in coda

Abhijit Menon-Sen ha consegnato una patch che implementa has_sequence_privilege().

Andrew (RhodiumToad) Gierth ha consegnato una patch per psql che aggiunge una menzione a ef nell’output del comando ? .

K. Srinath ha consegnato una patch che consente a un indice di coprire tutte le tabelle in una gerarchia ereditaria.

Pavel Stehule e Tom Lane hanno consegnato un paio di versioni di una patch che consente di lanciare un’eccezione da _PG_init, su base di una discussione precedente.

Heikki Linnakangas ha consegnato una patch che aiuta con la codifica dei messaggi.

Pavel Stehule ha consegnato una patch che trasforma gli input di array nelle funzioni variadiche in parametri standard.

Teodor Sigaev ha consegnato due patch per correggere un bug in GiST riportato da Andrew (RhodiumToad) Gierth.

Fujii Masao ha consegnato una nuova versione della sua patch a pg_standby per l’opzione trigger.

Robert Haas ha consegnato una patch per aggiungere SET NDISTINCT a ALTER COLUMN.

Bruce Momjian ha consegnato una nuova versione della sua patch che gestisce le piattaforme che non supportano effective_io_concurrency.

Martin Pihlak ha consegnato una patch che aggiunge un modificatore U (utente) ai comandi d di psql, in modo da fare il match dei pattern solo sugli oggetti non di sistema.

Alvaro Herrera ha consegnato una patch per correggere un bug reloptions segnalato da Khee Chin.

Teodor Sigaev ha consegnato una patch per correggere un crash nell’inserzione GiST di dati box patologici.

Zdenek Kotala ha consegnato una nuova patch per correggere il comportamento del getopt di Solaris.