Wöchentlicher PostgreSQL Newsletter - 05. Juni 2011
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== Wöchentlicher PostgreSQL Newsletter - 05. Juni 2011 ==
Die Austin Texas PUG trifft sich am Mittwoch, dem 8. Juni
um 18:30 Uhr. Pizza wird für angemeldete Personen verfügbar
sein. Anmeldung unter austinpug AT postgresql DOT org.
PGConf.DE 2011 ist die Deutschsprachige PostgreSQL Konferenz
und wird am 11. November 2011 im Rheinischen Industriemuseum
in Oberhausen, Deutschland, stattfinden. Der Call for Papers ist offen.
== PostgreSQL Produkt Neuigkeiten ==
devart dotConnect für PostgreSQL, ein
ADO.NET Treiber, ist erschienen.
MyJSQLView 3.29, ein GUI Werkzeug welches mit PostgreSQL verwendet
werden kann, ist erschienen.
PostgreDAC 2.6.3, ein Delphi/C++ Builder für PostgreSQL,
Slony-ctl 1.2.0, ein Set von Skripts zum Erstellen und Managen
von Slony Clustern, ist erschienen.
== PostgreSQL Jobs im Juni ==
== PostgreSQL Lokal ==
PG Session 2 über PostGIS findet am 23. Juni in Paris statt.
Der Call for Papers ist jetzt offen.
CHAR(11), die PostgreSQL Konferenz für Clustering, Hochverfügbarkeit
und Replikation hat jetzt die Registrierung eröffnet.
Die Konferenz findet am 11. und 12. Juli 2011 in Cambridge, UK statt.
PostgreSQL Conference China 2011 findet in Guangzhou am
15. und 16. Juli 2011 statt.
PDXPUG hostet PgDay am Sonntag, dem 24. Juli 2011, einen Tag
vor der OSCON in Portland, Oregon, USA. Details hier:
Postgres Open 2011, eine Konferenz die sich auf den Umbruch der
Datenbankindustrie durch PostgreSQL konzentriert, wird vom 14. bis 16.
September 2011 in Chicago, Illinois im Westin Michigan Avenue
PostgreSQL Conference West (#PgWest) findet vom 27. bis 30. September
2011 im San Jose Convention Center in Jan Jose, Kalifornen, USA statt.
PostgreSQL Conference Europe 2011 findet vom 18. bis
21. Oktober in Amsterdam statt.
pgbr findet in Sao Paulo, Brazilien, am 3. und 4. November 2011 statt.
== PostgreSQL in den News ==
Planet PostgreSQL: http://planet.postgresql.org/
Dieser wöchentliche PostgreSQL Newsletter wurde erstellt von David Fetter.
Sende Neuigkeiten und Ankündigungen bis Sonntag, 15 Uhr Pazifischer
Zeit. Bitte sende englische Beiträge an firstname.lastname@example.org, deutsche an
email@example.com, italienische an firstname.lastname@example.org, spanische an email@example.com.
== Reviews ==
== Angewandte Patches ==
Alvaro Herrera pushed:
- Make message more consistent
- Remove usage of &PL_sv_undef in hashes and arrays. According to
perlguts, &PL_sv_undef is not the right thing to use in those cases
because it doesn't behave the same way as an undef value via Perl
code. Seems the intuitive way to deal with undef values is subtly
enough broken that it's hard to notice when misused. The broken
uses got inadvertently introduced in commit
87bb2ade2ce646083f39d5ab3e3307490211ad04 by Alexey Klyukin, Alex
Hunsaker and myself on 2011-02-17; no backpatch is necessary. Per
testing report from Greg Mullane. Author: Alex Hunsaker
- Fix pg_get_constraintdef to cope with NOT VALID constraints. This
case was missed when NOT VALID constraints were first introduced in
commit 722bf7017bbe796decc79c1fde03e7a83dae9ada by Simon Riggs on
2011-02-08. Among other things, it causes pg_dump to omit the NOT
VALID flag when dumping such constraints, which may cause them to
fail to load afterwards, if they contained values failing the
constraint. Per report from Thom Brown.
Heikki Linnakangas pushed:
- The row-version chaining in Serializable Snapshot Isolation was
still wrong. On further analysis, it turns out that it is not
needed to duplicate predicate locks to the new row version at
update, the lock on the version that the transaction saw as visible
is enough. However, there was a different bug in the code that
checks for dangerous structures when a new rw-conflict happens. Fix
that bug, and remove all the row-version chaining related code.
Kevin Grittner & Dan Ports, with some comment editorialization by
- SSI comment fixes and enhancements. Notably, document that the
conflict-out flag actually means that the transaction has a conflict
out to a transaction that committed before the flagged transaction.
Magnus Hagander pushed:
- Don't include local line on platforms without support. Since we now
include a sample line for replication on local connections in
pg_hba.conf, don't include it where local connections aren't
available (such as on win32). Also make sure we use authmethodlocal
and not authmethod on the sample line.
- Refuse "local" lines in pg_hba.conf on platforms that don't support
it. This makes the behavior compatible with that of hostssl, which
also throws an error when there is no SSL support included.
- Don't recommend upgrading to latest available Windows SDK. We only
support up to version 7.0, so don't recommend upgrading past it.
The rest of the documentation around this was already updated, but
one spot was missed.
Peter Eisentraut pushed:
- Suppress foreign data wrappers and foreign servers in partial dumps.
This is consistent with the behavior of other global objects such as
languages and extensions. Omitting foreign servers also omits the
respective user mappings.
- Recode non-ASCII characters in source to UTF-8. For consistency,
have all non-ASCII characters from contributors' names in the source
be in UTF-8. But remove some other more gratuitous uses of
- Use entities to encode non-ASCII characters in SGML documentation.
This has already been the case for the most part; just some cases
had slipped through.
- Some copy editing of the release notes
- Sort COMMENT synopsis and add more examples. Josh Kupershmidt
- Truncate id to <=44 characters. This is the original DocBook SGML
limit, but apparently most installations have changed it or ignore
it, which is why few people have run into this problem. pointed out
by Brendan Jurd
Tom Lane pushed:
- Fix VACUUM so that it always updates pg_class.reltuples/relpages.
When we added the ability for vacuum to skip heap pages by
consulting the visibility map, we made it just not update the
reltuples/relpages statistics if it skipped any pages. But this
could leave us with extremely out-of-date stats for a table that
contains any unchanging areas, especially for TOAST tables which
never get processed by ANALYZE. In particular this could result in
autovacuum making poor decisions about when to process the table, as
in recent report from Florian Helmberger. And in general it's a bad
idea to not update the stats at all. Instead, use the previous
values of reltuples/relpages as an estimate of the tuple density in
unvisited pages. This approach results in a "moving average"
estimate of reltuples, which should converge to the correct value
over multiple VACUUM and ANALYZE cycles even when individual
measurements aren't very good. This new method for updating
reltuples is used by both VACUUM and ANALYZE, with the result that
we no longer need the grotty interconnections that caused ANALYZE to
not update the stats depending on what had happened in the parent
VACUUM command. Also, fix the logic for skipping all-visible pages
during VACUUM so that it looks ahead rather than behind to decide
what to do, as per a suggestion from Greg Stark. This eliminates
useless scanning of all-visible pages at the start of the relation
or just after a not-all-visible page. In particular, the first few
pages of the relation will not be invariably included in the scanned
pages, which seems to help in not overweighting them in the
reltuples estimate. Back-patch to 8.4, where the visibility map was
- Fix portability bugs in use of credentials control messages for peer
auth. Even though our existing code for handling credentials
control messages has been basically unchanged since 2001, it was
fundamentally wrong: it did not ensure proper alignment of the
supplied buffer, and it was calculating buffer sizes and message
sizes incorrectly. This led to failures on platforms where
alignment padding is relevant, for instance FreeBSD on 64-bit
platforms, as seen in a recent Debian bug report passed on by Martin
Rewrite to do the message-whacking using the macros specified in RFC
2292, following a suggestion from Theo de Raadt in that thread.
Tested by me on Debian/kFreeBSD-amd64; since OpenBSD and NetBSD
document the identical CMSG API, it should work there too.
Back-patch to all supported branches.
- Replace use of credential control messages with
getsockopt(LOCAL_PEERCRED). It turns out the reason we hadn't found
out about the portability issues with our credential-control-message
code is that almost no modern platforms use that code at all; the
ones that used to need it now offer getpeereid(), which we choose
first. The last holdout was NetBSD, and they added getpeereid() as
of 5.0. So far as I can tell, the only live platform on which that
code was being exercised was Debian/kFreeBSD, ie, FreeBSD kernel
with Linux userland --- since glibc doesn't provide getpeereid(), we
fell back to the control message code. However, the FreeBSD kernel
provides a LOCAL_PEERCRED socket parameter that's functionally
equivalent to Linux's SO_PEERCRED. That is both much simpler to use
than control messages, and superior because it doesn't require
receiving a message from the other end at just the right time.
Therefore, add code to use LOCAL_PEERCRED when necessary, and rip
out all the credential-control-message code in the backend. (libpq
still has such code so that it can still talk to pre-9.1 servers ...
but eventually we can get rid of it there too.) Clean up related
autoconf probes, too. This means that libpq's requirepeer parameter
now works on exactly the same platforms where the backend supports
peer authentication, so adjust the documentation accordingly.
- Protect GIST logic that assumes penalty values can't be negative.
Apparently sane-looking penalty code might return small negative
values, for example because of roundoff error. This will confuse
places like gistchoose(). Prevent problems by clamping negative
penalty values to zero. (Just to be really sure, I also made it
force NaNs to zero.) Back-patch to all supported branches.
- Further improvements in pg_ctl's new wait-for-postmaster-start
logic. Add a postmaster_is_alive() test to the wait loop, so that
we stop waiting if the postmaster dies without removing its pidfile.
Unfortunately this only helps after the postmaster has created its
pidfile, since until then we don't know which PID to check. But if
it never does create the pidfile, we can give up in a relatively
short time, so this is a useful addition in practice. Per
suggestion from Fujii Masao, though this doesn't look very much like
his patch. In addition, improve pg_ctl's ability to cope with
pre-existing pidfiles. Such a file might or might not represent a
live postmaster that is going to block our postmaster from starting,
but the previous code pre-judged the situation and gave up waiting
immediately. Now, we will wait for up to 5 seconds to see if our
postmaster overwrites such a file. This issue interacts with
Fujii's patch because we would make the wrong conclusion if we did
the postmaster_is_alive() test with a pre-existing PID. All of this
could be improved if we rewrote start_postmaster() so that it could
report the child postmaster's PID, so that we'd know a-priori the
correct PID to test with postmaster_is_alive(). That looks like a
bit too much change for so late in the 9.1 development cycle,
- Allow hash joins to be interrupted while searching hash table for
match. Per experimentation with a recent example, in which
unreasonable amounts of time could elapse before the backend would
respond to a query-cancel. This might be something to back-patch,
but the patch doesn't apply cleanly because this code was rewritten
for 9.1. Given the lack of field complaints I won't bother for now.
- Implement getpeereid() as a src/port compatibility function. This
unifies a bunch of ugly #ifdef's in one place. Per discussion, we
only need this where HAVE_UNIX_SOCKETS, so no need to cover Windows.
Marko Kreen, some adjustment by Tom Lane
- Typo fix.
- Disallow SELECT FOR UPDATE/SHARE on sequences. We can't allow this
because such an operation stores its transaction XID into the
sequence tuple's xmax. Because VACUUM doesn't process sequences
(and we don't want it to start doing so), such an xmax value won't
get frozen, meaning it will eventually refer to nonexistent pg_clog
storage, and even wrap around completely. Since the row lock is
ignored by nextval and setval, the usefulness of the operation is
highly debatable anyway. Per reports of trouble with pgpool 3.0,
which had ill-advisedly started using such commands as a form of
locking. In HEAD, also disallow SELECT FOR UPDATE/SHARE on toast
tables. Although this does work safely given the current
implementation, there seems no good reason to allow it. I refrained
from changing that behavior in back branches, however.
- Clean up after erroneous SELECT FOR UPDATE/SHARE on a sequence. My
previous commit disallowed this operation, but did nothing about
cleaning up the damage if one had already been done. With the
operation disallowed, it's okay to just forcibly clear xmax in a
sequence's tuple, since any value seen there could not represent a
live transaction's lock. So, any sequence-specific operation will
repair the problem automatically, whether or not the user has
already seen "could not access status of transaction" failures.
- libpq needs its own copy of src/port/getpeereid ... on some
platforms, anyway. Per buildfarm.
- Looks like we can't declare getpeereid on Windows anyway ... for
lack of the uid_t and gid_t typedefs. Per buildfarm.
- Handle domains when checking for recursive inclusion of composite
types. We need this now because we allow domains over arrays, and
we'll probably allow domains over composites pretty soon, which
makes the problem even more obvious. Although domains over arrays
also exist in previous versions, this does not need to be
back-patched, because the coding used in older versions successfully
"looked through" domains over arrays. The problem is exposed by not
treating a domain as having a typelem. Problem identified by Noah
Misch, though I did not use his patch, since it would require
additional work to handle domains over composites that way. This
approach is more future-proof.
- Need to list getpeereid.c in .gitignore, too ...
- Fix failure to check whether a rowtype's component types are
sortable. The existence of a btree opclass accepting composite
types caused us to assume that every composite type is sortable.
This isn't true of course; we need to check if the column types are
all sortable. There was logic for this for the case of array
comparison (ie, check that the element type is sortable), but we
missed the point for rowtypes. Per Teodor's report of an ANALYZE
failure for an unsortable composite type. Rather than just add some
more ad-hoc logic for this, I moved knowledge of the issue into
typcache.c. The typcache will now only report out array_eq,
record_cmp, and friends as usable operators if the array or
composite type will work with those functions. Unfortunately we
don't have enough info to do this for anonymous RECORD types; in
that case, just assume it will work, and take the runtime failure as
before if it doesn't. This patch might be a candidate for
back-patching at some point, but given the lack of complaints from
the field, I'd rather just test it in HEAD for now. Note: most of
the places touched in this patch will need further work when we get
around to supporting hashing of record types.
- Reset reindex-in-progress state before reverifying an exclusion
constraint. This avoids an Assert failure when we try to use
ordinary index fetches while checking for exclusion conflicts. Per
report from Noah Misch. No need for back-patch because the Assert
wasn't there before 9.1.
Robert Haas pushed:
- Avoid creating init fork for unlogged indexes when it already
exists. Report by Greg Sabino Mullane, diagnosis and preliminary
patch by Andres Freund, corrections by me.
- Fix vim-induced typo.
Bruce Momjian pushed:
- Use proper SGML doc entities rather than angle-brackets. Marco
== Abgelehnte Patches (bis jetzt) ==
No one was disappointed this week :-)
== Eingesandte Patches ==
Magnus Hagander sent in a patch to fix an infelicity in SSL handling
Florian Pflug sent in two revisions of a patch to fix a bug in XPATH()
when the expression returns a scalar value.
Heikki Linnakangas sent in a patch to fix an issue with SSI predicate
locking, changing from row to tuple.
Heikki Linnakangas sent in two revisions of a patch to fix some
infelicities in nested CASE-WHEN scoping.
Alvaro Herrera sent in four revisions of a patch to enable CHECK
constraints to be declared as NOT VALID, as FOREIGN KEY ones can now.
Radoslaw Smogura sent in a patch to create BLOBs and attendant
Mark Kirkwood sent in three revisions of a patch to add the ability to
constrain backend temporary file space.
Kevin Grittner sent in a patch to fix some comments in the SSI code.
Teodor Sigaev and Tom Lane traded patches to fix an issue with VACUUM
and composite row types.
Robert Haas sent in two revisions of a patch to clean up
Pavel Stehule sent in another revision of the patch to enhance GET
Andrew Chernow sent in two revisions of a patch to fix an issue in
Kevin Grittner sent in two revisions of a patch to fix an infelicity
in DDL under SSI.
Alexander Korotkov sent in a WIP patch to do a faster GiST index build.
Robert Haas sent in a WIP patch to reduce the overhead of frequent
Gurjeet Singh sent in two more revisions of a patch to allow psql to
include files relative to the current file.
Josh Kupershmidt sent in another revision of the patch to allow \dd to
show constraint comments in psql.
Pavel Stehule sent in a WIP patch to add some new diagnostics to
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