[DPWN] Wöchentlicher PostgreSQL Newsletter - 11. Februar 2007

Der Originalartikel befindet sich unter:

== Wöchentlicher PostgreSQL Newsletter - 11. Februar 2007 ==

Magnus Hagander und Joachim Wieland haben eine Doxygen Seite für den PostgreSQL Sourcecode erstellt.

Magnus Hagander ist jetzt ein Commiter. Glückwünsche!

Simon Riggs fing eine neue Diskussion über HOT-Tables – Tabellen, die für extrem frequentierte Updates optimiert sind – mit seinem vereinfachten Antrag für das Design und die Implementierung derselben an.

== PostgreSQL Product News ==

GNUmed Version erschienen.

Pgpool 3.2 ist draussen:

Peter Eisentraut hat die Funktionen sql_to_xml(TEXT) table_to_xmlschema(TEXT) implementiert, welche die zugrundeliegenden XML Datentypen in CVS TIP benutzen.

MicroOLAP Database Designer 1.2.0 BETA 1 für PostgreSQL erschienen.

ht://Miner 0.50 erschienen.

== PostgreSQL Jobs im Februar ==


== PostgreSQL Lokal ==

Es wird einen PostgreSQL Stand auf dem CLT am 3.-4. März in Chemnitz/Deutschland geben. Einige der üblichen Verdächtigen der deutschsprachigen PostgreSQl Community werden dort sein. Kontaktiere info@pgug.de für mehr Informationen.

Es wird einen PostgreSQL Stand auf der FOSDEM am 24. und 25. Februar in Brüssel, Belgien sein. Viele der üblichen Verdächtigen von den EU PostgreSQL Communities werden dort sein. Kontaktiere de@postgresql.org für mehr Informationen.

Die italienische PostgreSQL Community ist auf der Suche nach Sponsoren für ihren PostgreSQL Tag in Prato, Italien im Sommer. Mehr Informationen unter untenstehendem Link.

== PostgreSQL in den News ==

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

General Bits, Archive und gelegentliche News Artikel:

Dieser wöchentliche PostgreSQL Newsletter wurde erstellt von David Fetter, Devrim GUNDUZ und Stefan Kaltenbrunner

Um deine Beiträge für die nächste Ausgabe zu übermitteln, sende diese an david@fetter.org bis Sonntag, 15:00 Uhr Pazifischer Zeit.

== Angewandte Patches ==

Magnus Hagander (kudos!) committed:

  • 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 committed:

  • 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 committed:

  • Heikki Linnakangas’s patch which fixes reference-after-free in the
    new btree page split code, as reported by the buildfarm via Stefan

  • Magnus Hagander’s patch which the VC++ build needs to compile the
    new strlcat.c file.

Michael Meskes committed:

  • 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 committed:

  • Add support for optionally escaping periods when converting SQL
    identifiers to XML names, which will be required for supporting XML

  • 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

  • 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 committed:

  • Update FAQ for new 24-byte header, down from 28.

  • Mark TODO as done: “Merge xmin/xmax/cmin/cmax back into three header

  • 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

  • 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

  • Gavin Sherry’ patch which checks whether the role exists before
    doing more complex ident and Kerberos authentication checks in the

  • 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

  • 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 committed:

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

Tom Lane committed:

  • Fix another erroneous =-for-:= substitution.

  • Improve documentation for CREATE CONSTRAINT TRIGGER.

  • Put back some not-so-unnecessary-as-all-that := usages. Per

  • 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

  • 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

  • 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

  • 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

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

  • 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
    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.

== Abgelehnte Patches (bis jetzt) ==

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

== Eingesandte Patches ==

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

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!

Zum Artikel im Blog…

Datum: Mon, 12 Feb 2007 22:53:38 +0100