PostgreSQL Weekly News | Nouvelles neuves de PG

Par SAS le 12/02/2007 - 23:02

Nouvelles hebdomadaires de PostgreSQL - 11 février 2007

Magnus Hagander et Joachim Wieland ont mis en place un site doxygen pour le code de PostgreSQL.
http://doxygen.postgresql.org/

Magnus Hagander est désormais committer. Félicitations !

Simon Riggs a démarré une nouvelle discussion concernant les « HOT tables Â» --tables optimisées pour les actualisations très fréquentes-- à partir de sa proposition simplifiée de conception et d'implantation.

Les nouveautés des produits dérivés

• GNUmed version 0.2.4.2 réalisé.
• Pgpool 3.2 est sorti&nbsp:
  http://pgfoundry.org/projects/pgpool
• Peter Eisentraut a implanté les fonctions sql_to_xml(TEXT) et table_to_xmlschema(TEXT) qui utilisent les types de données XML du CVS.
• MicroOLAP Database Designer 1.2.0 BETA 1 pour PostgreSQL est réalisé :
  http://microolap.com/products/database/postgresql-designer/
• ht://Miner 0.50 est réalisé :
  http://sourceforge.net/projects/htminer/

Les jobs PostgreSQL de février

http://archives.postgresql.org/pgsql-jobs/2007-02/threads.php

PostgreSQL Local

Il y aura un stand PostgreSQL les 3 et 4 mars à Chemnitz, RFA. Quelques personnalités incontournables des communautées PostgreSQL de langue allemande y seront. Contacter info@pgug.de pour en être.
http://chemnitzer.linux-tage.de/2007/info/

Il y aura un stand PostgreSQL au FOSDEM les 24 et 25 février ) Bruxelles, Belgique. La plupart des personnalités incontournables des communautés européennes y seront. Contacter de@postgresql.org pour participer.
http://www.fosdem.org/2007/

La communauté PostgreSQL italienne recherche des mécènes pour la journée PostgreSQL du Prato, Italie, cet été. Suivre le lien pour participer :
http://www.pgday.it

PostgreSQL dans les média

• Planet PostgreSQL :
  http://www.planetpostgresql.org/
• General Bits, Archives et nouveaux articles :
  http://www.varlena.com/GeneralBits/

PostgreSQL Weekly News vous est présenté cette semaine par David Fetter, Devrim GUNDUZ et Stefan Kaltenbrunner.
Adaptation francophone de Stéphane Schildknecht.

Vos propositions d'informations doivent parvenir avant dimanche minuit à david@fetter.org.

Correctifs appliqués

Magnus Hagander (félicitations !) a commité :

• Fix pg_standby to build on msvc.
• Fix for early log messages during postmaster startup getting lost when running as a service on Win32. Per report from Harald Armin Massa. Backpatched to PostgreSQL 8.1.

Neil Conway a commité :

• Unbreak the SGML doc build: ":=" is needed to assign to variables if the RHS of the assignment expands to a reference to the LHS.

Alvaro Herrera a commité :

• Heikki Linnakangas's patch which fixes reference-after-free in the new btree page split code, as reported by the buildfarm via Stefan Kaltenbrunner.
• Magnus Hagander's patch which the VC++ build needs to compile the new strlcat.c file.

Michael Meskes a commité :

• Fixed multibyte handling in ecpg per report from HARADA Toshi.
• Backported regression test changes from HEAD so the buildfarm hopefully gets green again.
• Backported va_list handling cleanup for ecpg.

Peter Eisentraut a commité :

• Add support for optionally escaping periods when converting SQL identifiers to XML names, which will be required for supporting XML export.
• Add proper mapping of boolean type data to XML Schema.
• StrNCpy -> strlcpy (not complete)
• Remove useless CPPFLAGS.
• Add $PostgreSQL$ marker to contrib makefiles.
• Replace useless uses of := by = in makefiles.
• Normalize fgets() calls to use sizeof() for calculating the buffer size where possible, and fix some sites that apparently thought that fgets() will overwrite the buffer by one byte. Also add some strlcpy() to eliminate some weird memory handling.
• Replace some strncpy() with strlcpy().
• Use memcpy() instead of strncpy() for copying into varlena structures.
• Add strlcat() from OpenBSD, to be used for replacing strncat and other strange coding practices.
• Move NAMEDATALEN definition from postgres_ext.h to pg_config_manual.h. It used to be part of libpq's exported interface many releases ago, but now it's no longer necessary to make it accessible to clients.

Bruce Momjian a commité :

• Update FAQ for new 24-byte header, down from 28.
• Mark TODO as done: "Merge xmin/xmax/cmin/cmax back into three header fields."
• In pgsql/src/backend/utils/adt/formatting.c, remove blank line from source code.
• Add to TODO: "Consider placing all sequences in a single table or create a system view, now that system tables are full transactional"
• Add URL for "Add support for SQL-standard GENERATED/IDENTITY columns" to TODO list.
• Pavel Stehule's patch which fixes a bug when localized to_char() day or month names were incorectly transformed to lower or upper string.
• Korry Douglas's patch which fixes shared_preload_libraries on Windows hosts. It forces each backend to re-load all shared_preload_libraries.
• Teodor Sigaev's patch which adds a lock matrix to documentation.
• Magnus Hagander's Win32 regression test fixes. For win32 in general, this makes it possible to run the regression tests as an admin user by using the same restricted token method that's used by pg_ctl and initdb. For vc++, it adds building of pg_regress.exe, adds a resultmap, and fixes how it runs the install.
• Simon Riggs's patch which adds /contrib/pg_standby. pg_standby is a production-ready program that can be used to create a Warm Standby server. Other configuration is required as well, all of which is described in the main server manual.
• Heikki Linnakangas's patch which reduces WAL activity for page splits.
• Gavin Sherry' patch which checks whether the role exists before doing more complex ident and Kerberos authentication checks in the backend.
• Update URL for "Generalized Partial Indexes" paper to point to a cached version. Backpatch to 8.2.X.
• Document that wal_sync_method open_* methods use O_DIRECT, if available. Backpatch to 8.2.X.
• Fix bug in our code when using to_timestamp() or to_date() without "TM". Assume "TM" when input fields are variable-length, like month or day names. This matches Oracle behavior.
• Stamp bug template for 8.3.
• Stamp releases notes for 8.2.3, 8.1.8, 8.0.12.
• Stamp releases 8.2.3, 8.1.8, 8.0.12. No release notes yet.
• Update FAQ for 8.2.3.
• Backpatch FAQs to 8.2.X branch.
• Update FAQ to show 8.2.2 as the most recent release.
• Update timezone FAQ.
• In TODO, split NAMEDATALEN entry into two parts. The one still on the TODO list is, "Consider making NAMEDATALEN more configurable in future releases."
• Trim down environment variable instructions for Win32, backpatch to 8.2.X.
• Add TODO item: "Add a \set variable to control whether \s displays line numbers."
• Clarify TODO item for \# feature: "Add \# to list command history like \s, but with line numbers"

Andrew Dunstan a commité :

• Pass modern COPY syntax to backend, since copy (query) does not accept old syntax. Per complaint from Michael Fuhr.

Tom Lane a commité :

• Fix another erroneous =-for-:= substitution.
• Improve documentation for CREATE CONSTRAINT TRIGGER.
• Put back some not-so-unnecessary-as-all-that := usages. Per buildfarm.
• Hm, seems my hack on rowtypes regression test has made its output row order platform-specific. Add an ORDER BY clause to stop buildfarm failures.
• Minor tweak to make rowtypes regression test run faster. We don't currently have any better strategy for this query than re-running the sub-select over and over; it seems unlikely that doing so 10000 times is a more useful test than doing it a few dozen times.
• Call pgstat_drop_database during DROP DATABASE, so that any stats file entries for the victim database go away sooner rather than later. We already did the equivalent thing at the per-relation level, not sure why it's not been done for whole databases. With this change, pgstat_vacuum_tabstat should usually not find anything to do; though we still need it as a backstop in case DROPDB or TABPURGE messages get lost under load.
• Combine cmin and cmax fields of HeapTupleHeaders into a single field, by keeping private state in each backend that has inserted and deleted the same tuple during its current top-level transaction. This is sufficient since there is no need to be able to determine the cmin/cmax from any other transaction. This gets us back down to 23-byte headers, removing a penalty paid in 8.0 to support subtransactions. Patch by Heikki Linnakangas, with minor revisions by moi, following a design hashed out awhile back on the pghackers list.
• Add missing #define for mingw, per Magnus.
• Fix an ancient logic error in plpgsql's exec_stmt_block: it thought it could get away with not (re)initializing a local variable if the variable is marked "isconst" and not "isnull". Unfortunately it makes this decision after having already freed the old value, meaning that something like
  
for i in 1..10 loop declare c constant text := 'hi there';

  leads to subsequent accesses to freed memory, and hence probably crashes. (In particular, this is why Asif Ali Rehman's bug leads to crash and not just an unexpectedly-NULL value for SQLERRM: SQLERRM is marked CONSTANT and so triggers this error.) The whole thing seems wrong on its face anyway: CONSTANT means that you can't change the variable inside the block, not that the initializer expression is guaranteed not to change value across successive block entries. Hence, remove the "optimization" instead of trying to fix it.

• Rearrange use of plpgsql_add_initdatums() so that only the parsing of a DECLARE section needs to know about it. Formerly, everyplace besides DECLARE that created variables needed to do "plpgsql_add_initdatums(NULL)" to prevent those variables from being sucked up as part of a subsequent DECLARE block. This is obviously error-prone, and in fact the SQLSTATE/SQLERRM patch had failed to do it for those two variables, leading to the bug recently exhibited by Asif Ali Rehman: a DECLARE within an exception handler tried to reinitialize SQLERRM. Although the SQLSTATE/SQLERRM patch isn't in any pre-8.1 branches, and so I can't point to a demonstrable failure there, it seems wise to back-patch this into the older branches anyway, just to keep the logic similar to HEAD.
• Add a function pg_stat_clear_snapshot() that discards any statistics snapshot already collected in the current transaction; this allows plpgsql functions to watch for stats updates even though they are confined to a single transaction. Use this instead of the previous kluge involving pg_stat_file() to wait for the stats collector to update in the stats regression test. Internally, decouple storage of stats snapshots from transaction boundaries; they'll now stick around until someone calls pgstat_clear_snapshot --- which xact.c still does at transaction end, to maintain the previous behavior. This makes the logic a lot cleaner, at the price of a couple dozen cycles per transaction exit.
• Modify the stats regression test to delay until the stats file actually changes (with an upper limit of 30 seconds), and record the delay time in the postmaster log. This should give us some info about what's happening with the intermittent stats failures in buildfarm. After an idea of Andrew Dunstan's.
• Remove the xlog-centric "database system is ready" message and replace it with "database system is ready to accept connections", which is issued by the postmaster when it really is ready to accept connections. Per proposal from Markus Schiltknecht and subsequent discussion.
• Fix PG_VERSION_NUM too.
• Fix wrong spacing (I think Bruce tried to hand-edit this instead of letting autoconf do it)
• Fix an error in the original coding of holdable cursors: PersistHoldablePortal thought that it didn't have to reposition the underlying tuplestore if the portal is atEnd. But this is not so, because tuplestores have separate read and write cursors ... and the read cursor hasn't moved from the start. This mistake explains bug #2970 from William Zhang. Note: the coding here is pretty inefficient, but given that no one has noticed this bug until now, I'd say hardly anyone uses the case where the cursor has been advanced before being persisted. So maybe it's not worth worrying about.
• Remove typmod checking from the recent security-related patches. It turns out that ExecEvalVar and friends don't necessarily have access to a tuple descriptor with correct typmod: it definitely can contain -1, and possibly might contain other values that are different from the Var's value. Arguably this should be cleaned up someday, but it's not a simple change, and in any case typmod discrepancies don't pose a security hazard. Per reports from numerous people :-( I'm not entirely sure whether the failure can occur in 8.0 --- the simple test cases reported so far don't trigger it there. But back-patch the change all the way anyway.
• In pgsql/src/backend/port/sysv_shmem.c, fix typo in comment.
• Heikki Linnakangas's patch to remove some dead code in src/backend/access/nbtree/nbtinsert.c
• Fix a performance regression in 8.2: optimization of MIN/MAX into indexscans had stopped working for tables buried inside views or sub-selects. This is because I had gotten rid of the simplify_jointree() preprocessing step, and optimize_minmax_aggregates() wasn't smart enough to deal with a non-canonical FromExpr. Per gripe from Bill Howe.
• Docs updates for cross-type hashing.
• Come to think of it, we should check that commutator pairs have the same merges/hashes property settings.
• Not only did we agree that this 'hint' doesn't belong here, but the markup's broken. So just remove it...
• Add support for cross-type hashing in hashed subplans (hashed IN/NOT IN cases that aren't turned into true joins). Since this is the last missing bit of infrastructure, go ahead and fill out the hash integer_ops and float_ops opfamilies with cross-type operators. The operator family project is now DONE...er, except for documentation...
• Repair failure to check that a table is still compatible with a previously made query plan. Use of ALTER COLUMN TYPE creates a hazard for cached query plans: they could contain Vars that claim a column has a different type than it now has. Fix this by checking during plan startup that Vars at relation scan level match the current relation tuple descriptor. Since at that point we already have at least AccessShareLock, we can be sure the column type will not change underneath us later in the query. However, since a backend's locks do not conflict against itself, there is still a hole for an attacker to exploit: he could try to execute ALTER COLUMN TYPE while a query is in progress in the current backend. Seal that hole by rejecting ALTER TABLE whenever the target relation is already open in the current backend. This is a significant security hole: not only can one trivially crash the backend, but with appropriate misuse of pass-by-reference datatypes it is possible to read out arbitrary locations in the server process's memory, which could allow retrieving database content the user should not be able to see. Our thanks to Jeff Trout for the initial report. Security: CVE-2007-0556
• Repair insufficiently careful type checking for SQL-language functions: we should check that the function code returns the claimed result datatype every time we parse the function for execution. Formerly, for simple scalar result types we assumed the creation-time check was sufficient, but this fails if the function selects from a table that's been redefined since then, and even more obviously fails if check_function_bodies had been OFF. This is a significant security hole: not only can one trivially crash the backend, but with appropriate misuse of pass-by-reference datatypes it is possible to read out arbitrary locations in the server process's memory, which could allow retrieving database content the user should not be able to see. Our thanks to Jeff Trout for the initial report. Security: CVE-2007-0555
• Rename MaxTupleSize to MaxHeapTupleSize to clarify that it's not meant to describe the maximum size of index tuples (which is typically AM-dependent anyway); and consequently remove the bogus deduction for "special space" that was built into it. Adjust TOAST_TUPLE_THRESHOLD and TOAST_MAX_CHUNK_SIZE to avoid wasting two bytes per toast chunk, and to ensure that the calculation correctly tracks any future changes in page header size. The computation had been inaccurate in a way that didn't cause any harm except space wastage, but future changes could have broken it more drastically. Fix the calculation of BTMaxItemSize, which was formerly computed as 1 byte more than it could safely be. This didn't cause any harm in practice because it's only compared against maxalign'd lengths, but future changes in the size of page headers or btree special space could have exposed the problem. initdb forced because of change in TOAST_MAX_CHUNK_SIZE, which alters the storage of toast tables.

Correctifs rejetés, à ce jour

Chris Marcellino's patch to add POSIX shared memory support because it doesn't actually detect whether a shared memory segment is in use.

Correctifs en attente

• Two versions of Simon Riggs's patch which moves a warning in VACUUM to a spot after lazy_truncate_heap(). Both move the test and WARNING. The second also adjusts the hint according to relation size.
• Guido Goldstein's revised patch which fixes PL/PythonU's handling of BOOLEAN return functions and, unlike the previous patch, is designed to work with Python 2.3 as well as later versions.
• Gregory Stark sent in a patch to speed up LIMIT/SORT operations, as typically used in paging out result sets.
• Simon Riggs sent in a patch to speed up CLUSTER by avoiding WAL when archive_command is not set.
• Gregory Stark sent in another work-in-progress patch which implements WITH RECURSIVE.
• Chad Wagner sent in a patch which lets psql prompt for variables.
• Chris Marcellino sent in a patch to make OS/X use SysV semaphors.
• Heikki Linnakangas sent in a patch which refactors findsplitloc and checksplitloc so that the division of labor is clearer. All the space calculation inside the loop is now in checksplitloc.
• Jeremy Drake sent in a patch which implements regexp_replace with multiple atoms, regexp_matches, a set-returning function, and regexp_split. Perl weenies rejoice!