== PostgreSQL Weekly News - October 30 2011 ==
The Call for Papers is open for PostgreSQL Session #3, which will be
held in Paris, Feb 2nd, 2012. The deadline for proposals is the 30th
November 2011 and selected speakers will be notified by the 14th
December 2011. Proposals (in French or English) should be submitted
to call-for-paper AT postgresql-sessions DOT org.
More information at: http://www.postgresql-sessions.org/en/3/
== PostgreSQL Product News ==
Benetl 3.8, an ETL tool for files using PostgreSQL, released.
PL/Proxy 2.3.0, a write-scaling clustering system for PostgreSQL, released.
Pyrseas 0.4.1, a toolkit for PostgreSQL version control, released on PGXN.
== PostgreSQL Jobs for October ==
== PostgreSQL Local ==
pgbr will be in Sao Paulo, Brazil November 3-4, 2011.
PGConf.DE 2011, the German-speaking PostgreSQL Conference, will
take place on November 11th in the Rheinisches Industriemuseum in
Oberhausen, Germany. The schedule is now available, and registration
The fifth edition of the Italian PostgreSQL Day (PGDay.IT 2011) will
be held on November 25, 2011 in Prato, Italy.
The Call for Papers for is open for FLOSS UK, which will be held in
Edinburgh from the 20th to the 22nd March 2012. The deadline for
proposals is the 18th November 2011 and selected speakers will be
notified by the 25th November 2011. Proposals should be submitted to
postgresql2012 AT flossuk DOT org. More information at:
== PostgreSQL in the News ==
Planet PostgreSQL: http://planet.postgresql.org/
PostgreSQL Weekly News is brought to you this week by David Fetter
Submit news and announcements by Sunday at 3:00pm Pacific time.
Please send English language ones to david(at)fetter(dot)org, German language
to pwn(at)pgug(dot)de, Italian language to pwn(at)itpug(dot)org(dot) Spanish language
== Reviews ==
== Applied Patches ==
Magnus Hagander pushed:
- Make TABLE tab complation in psql include all relations. Not just
tables, since views also work fine with the TABLE command.
- Support configurable eventlog application names on Windows. This
allows different instances to use the eventlog with different
identifiers, by setting the event_source GUC, similar to how
syslog_ident works. Original patch by MauMau, heavily modified by
- Remove argument decoration that appears unsupported on mingw
- Make event_source visible on all platforms. On non-windows
platform, we just ignore any value set there. Noted by Jaime
- Fix typo
- MingW doesn't support wcstombs_s()...
- Implement streaming xlog for backup tools. Add option for parallel
streaming of the transaction log while a base backup is running, to
get the logfiles before the server has removed them. Also add a
tool called pg_receivexlog, which streams the transaction log into
files, creating a log archive without having to wait for segments to
complete, thus decreasing the window of data loss without having to
waste space using archive_timeout. This works best in combination
with archive_command - suggested usage docs etc coming later.
Alvaro Herrera pushed:
- Add debugging aid in isolationtester
Tom Lane pushed:
- Change FK trigger creation order to better support self-referential
FKs. When a foreign-key constraint references another column of the
same table, row updates will queue both the PK's ON UPDATE action
and the FK's CHECK action in the same event. The ON UPDATE action
must execute first, else the CHECK will check a non-final state of
the row and possibly throw an inappropriate error, as seen in bug
#6268 from Roman Lytovchenko. Now, the firing order of multiple
triggers for the same event is determined by the sort order of their
pg_trigger.tgnames, and the auto-generated names we use for FK
triggers are "RI_ConstraintTrigger_NNNN" where NNNN is the trigger
OID. So most of the time the firing order is the same as creation
order, and so rearranging the creation order fixes it. This patch
will fail to fix the problem if the OID counter wraps around or adds
a decimal digit (eg, from 99999 to 100000) while we are creating the
triggers for an FK constraint. Given the small odds of that, and
the low usage of self-referential FKs, we'll live with that solution
in the back branches. A better fix is to change the auto-generated
names for FK triggers, but it seems unwise to do that in stable
branches because there may be client code that depends on the naming
convention. We'll fix it that way in HEAD in a separate patch.
Back-patch to all supported branches, since this bug has existed for
a long time.
- Change FK trigger naming convention to fix self-referential FKs.
Use names like "RI_ConstraintTrigger_a_NNNN" for FK action triggers
and "RI_ConstraintTrigger_c_NNNN" for FK check triggers. This
ensures the action trigger fires first in self-referential cases
where the very same row update fires both an action and a check
trigger. This change provides a non-probabilistic solution for bug
#6268, at the risk that it could break client code that is making
assumptions about the exact names assigned to auto-generated FK
triggers. Hence, change this in HEAD only. No need for forced
initdb since old triggers continue to work fine.
- Improve planner's ability to recognize cases where an IN's RHS is
unique. If the right-hand side of a semijoin is unique, then we can
treat it like a normal join (or another way to say that is: we don't
need to explicitly unique-ify the data before doing it as a normal
join). We were recognizing such cases when the RHS was a sub-query
with appropriate DISTINCT or GROUP BY decoration, but there's
another way: if the RHS is a plain relation with unique indexes, we
can check if any of the indexes prove the output is unique. Most of
the infrastructure for that was there already in the join removal
code, though I had to rearrange it a bit. Per reflection about a
recent example in pgsql-performance.
- Typo fixes. expect -> except, noted by Andrew Dunstan. Also,
"cannot" seems more readable here than "can not", per David Wheeler.
- Add simple script to check for right recursion in Bison grammars.
We should generally use left-recursion not right-recursion to parse
lists. Bison hasn't got any built-in way to check for this type of
inefficiency, and I didn't find anything on the net in a quick
search, so I wrote a little Perl script to do it. Add to src/tools/
so we don't have to re-invent this wheel next time we wonder if
we're doing anything stupid. Currently, the only place that seems
to need fixing is plpgsql's stmt_else production, so the problem
doesn't appear to be common enough to warrant trying to include such
a test in our standard build process. If we did want to do that,
we'd need a way to ignore some false positives, such as a_expr :=
- Avoid recursion while processing ELSIF lists in plpgsql. The
original implementation of ELSIF in plpgsql converted the construct
into nested simple IF statements. This was prone to stack overflow
with long ELSIF lists, in two different ways. First, it's difficult
to generate the parsetree without using right-recursion in the bison
grammar, and that's prone to parser stack overflow since nothing can
be reduced until the whole list has been read. Second, we'd recurse
during execution, thus creating an unnecessary risk of
execution-time stack overflow. Rewrite so that the ELSIF list is
represented as a flat list, scanned via iteration not recursion, and
generated through left-recursion in the grammar. Per a gripe from
- Update docs to point to the timezone library's new home at IANA.
The recent unpleasantness with copyrights has accelerated a move
that was already in planning.
- De-parallelize ecpg build some more. Make sure ecpg/include/ is
rebuilt before the other subdirectories, so that ecpg_config.h is up
to date. This is not likely to matter during production builds,
only development, so no back-patch.
- Fix assorted bogosities in cash_in() and cash_out(). cash_out
failed to handle multiple-byte thousands separators, as per bug
#6277 from Alexander Law. In addition, cash_in didn't handle that
either, nor could it handle multiple-byte positive_sign. Both
routines failed to support multiple-byte mon_decimal_point, which I
did not think was worth changing, but at least now they check for
the possibility and fall back to using '.' rather than emitting
invalid output. Also, make cash_in handle trailing negative signs,
which formerly it would reject. Since cash_out generates trailing
negative signs whenever the locale tells it to, this last omission
represents a fail-to-reload-dumped-data bug. IMO that justifies
patching this all the way back.
- Further improvement of make_greater_string. Make sure that it
considers all the possibilities that the old code did, instead of
trying only one possibility per character position. To keep the
runtime in bounds, instead tweak the character incrementers to not
try every possible multibyte character code. Remove unnecessary
logic to restore the old character value on failure. Additional
comment and formatting cleanup.
- Support more locale-specific formatting options in cash_out(). The
POSIX spec defines locale fields for controlling the ordering of the
value, sign, and currency symbol in monetary output, but cash_out
only supported a small subset of these options. Fully implement
p/n_sign_posn, p/n_cs_precedes, and p/n_sep_by_space per spec. Fix
up cash_in so that it will accept all these format variants. Also,
make sure that thousands_sep is only inserted to the left of the
decimal point, as required by spec. Per bug #6144 from Eduard
Kracmar and discussion of bug #6277. This patch includes some ideas
from Alexander Lakhin's proposed patch, though it is very different
Bruce Momjian pushed:
- Fix pg_bsd_indent bug where newlines were not being trimmed from
typedef lines. Update pg_bsd_indent required version to 1.1 (and
update ftp site). Problem reported by Magnus Hagander.
- Update pg_upgrade testing instructions.
- Clarify pg_upgrade error message that the 'postgres' database must
exist in the old cluster.
- Remove pg_upgrade dependency on the 'postgres' database existing in
the new cluster. vacuumdb, used by pg_upgrade, still has this
Heikki Linnakangas pushed:
- Fix the number of lwlocks needed by the "fast path" lock patch. It
needs one lock per backend or auxiliary process - the need for a
lock for each aux processes was not accounted for in NumLWLocks().
No-one noticed, because the three locks needed for the three aux
processes fit into the few extra lwlocks we allocate for 3rd party
modules that don't call RequestAddinLWLocks()
(NUM_USER_DEFINED_LWLOCKS, 4 by default).
Robert Haas pushed:
- Change "and and" to "and". Report by Vik Reykja, patch by Kevin
- Clarify that ORDER BY/FOR UPDATE can't malfunction at higher iso
levels. Kevin Grittner
- Remove hard-coded "\connect postgres" from pg_dumpall. This doesn't
appear to accompish anything useful, and does make the restore fail
if the postgres database happens to have been dropped.
- Demote some sanity checks in BufferIsValid() to assertions. Testing
reveals that this macro is a hot-spot for index-only-scans. Per
discussion with Tom Lane.
- Allow hint bits to be set sooner for temporary and unlogged tables.
We need not wait until the commit record is durably on disk, because
in the event of a crash the page we're updating with hint bits will
be gone anyway. Per off-list report from Heikki Linnakangas, this
can significantly degrade the performance of unlogged tables; I was
able to show a 2x speedup from this patch on a pgbench run with
scale factor 15. In practice, this will mostly help small, heavily
updated tables, because on larger tables you're unlikely to run into
the same row again before the commit record makes it out to disk.
- Improve make_greater_string() with encoding-specific incrementers.
This infrastructure doesn't in any way guarantee that the character
we produce will sort before the one we incremented; but it does at
least make it much more likely that we'll end up with something that
is a valid character, which improves our chances. Kyotaro
Horiguchi, with various adjustments by me.
- Update visibilitymap.c header comments. Recent work on index-only
scans left this somewhat out of date.
== Rejected Patches (for now) ==
No one was disappointed this week :-)
== Pending Patches ==
Fujii Masao and Jun Ishiduka traded revisions of the patch to allow
taking a base backup from a hot standby.
Shigeru HANADA sent in two revisions of patches for a PostgreSQL FDW,
along with some generic helper functions and new documentation on how
to write FDWs.
Heikki Linnakangas sent in another revision of the patch to add
multiple tuples at once in COPY.
Simon Riggs sent in two revisions of a patch to fix an issue where hot
backup fails at rsync fails at pg_clog when under load.
Kerem Kat sent in another revision of the patch to add CORRESPONDING
TO set operations.
Pavel Stehule sent in another revision of the patch that allows
PL/pgsql to make arrays of any %TYPE declared.
Alexander Korotkov sent in another revision of the patch to collect
statistics for array columns.
Robert Haas sent in a couple of patches he was using to analyze the
slowness of COUNT(*) in the index-only scan case.
Simon Riggs sent in two revisions of a patch to speed up hot standbys
in the subtransaction case.
Robert Haas sent in a patch to speed up unlogged tables.
Robert Haas sent in a patch that initializes each PGPROC's myProcLocks
just once at postmaster startup rather than every time the PGPROC is
handed out to a backend.
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