== PostgreSQL Weekly News – April 08 2012 ==
== PostgreSQL Weekly News – April 08 2012 ==
== PostgreSQL Product News ==
LuaPgSQL, a Lua binding for PostgreSQL, released:
== PostgreSQL Jobs for April ==
== PostgreSQL Local ==
London PostgreSQL Evening Meetup, 17 April 2012
PGCon 2012 will be held 17-18 May 2012, in Ottawa at the University of
Ottawa. It will be preceded by two days of tutorials on 15-16 May 2012.
PGDay France will be in Lyon on June 7, 2012.
== PostgreSQL in the News ==
Planet PostgreSQL: http://planet.postgresql.org/
PostgreSQL Weekly News is brought to you this week by David Fetter
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== Applied Patches ==
Peter Eisentraut pushed:
– Add support for renaming domain constraints
– NLS: Use msgmerge/xgettext –no-wrap and –sort-by-file. The option
–no-wrap prevents wars with (most?) editors about proper line
wrapping. –sort-by-file ensures consistent file order, for easier
– Correct various system catalog/view definitions in the
documentation. Thom Brown
– Fix some typos in the documentation. Thom Brown
Robert Haas pushed:
– Arrange for on_exit_nicely to be thread-safe. Extracted from
Joachim Wieland’s parallel pg_dump patch, with some additional
comments by me.
– Expose track_iotiming data via the statistics collector. Ants
Aasma’s original patch to add timing information for buffer I/O
requests exposed this data at the relation level, which was judged
too costly. I’ve here exposed it at the database level instead.
– Correctly explain units used by function-timing stats functions.
The views are in milliseconds, but the raw functions return
– Publish checkpoint timing information to pg_stat_bgwriter. Greg
Smith, Peter Geoghegan, and Robert Haas
– Allow pg_archivecleanup to strip optional file extensions. Greg
Smith and Jaime Casanova, reviewed by Alex Shulgin and myself.
– checkopint -> checkpoint. Report by Guillaume Lelarge.
– Put back code inadvertently deleted from exit_nicely. Report by
– Teach SLRU code to avoid replacing I/O-busy pages. Patch by me;
review by Tom Lane and others.
Tom Lane pushed:
– Fix a couple of contrib/dblink bugs. dblink_exec leaked temporary
database connections if any error occurred after connection setup,
for example SELECT dblink_exec(‘…connect string…’, ‘select
1/0’); Add a PG_TRY block to ensure PQfinish gets done when it is
needed. (dblink_record_internal is on the hairy edge of needing
similar treatment, but seems not to be actively broken at the
moment.) Also, in 9.0 and up, only one of the three functions using
tuplestore return mode was properly checking that the query context
would allow a tuplestore result. Noted while reviewing dblink
patch. Back-patch to all supported branches.
– Fix syslogger to not lose log coherency under high load. The
original coding of the syslogger had an arbitrary limit of 20 large
messages concurrently in progress, after which it would just punt
and dump message fragments to the output file separately. Our
ambitions are a bit higher than that now, so allow the data
structure to expand as necessary. Reported and patched by Andrew
Dunstan; some editing by Tom
– Remove useless PGRES_COPY_BOTH “support” in psql. There is no
existing or foreseeable case in which psql should see a
PGRES_COPY_BOTH PQresultStatus; and if such a case ever emerges,
it’s a pretty good bet that these code fragments wouldn’t do the
right thing anyway. Remove them, and let the existing default cases
do the appropriate thing, namely emit an “unexpected PQresultStatus”
bleat. Noted while working on libpq row processor patch, for which
I was considering adding a PGRES_SUSPENDED status code — the same
default-case treatment would be appropriate for that.
– Add a “row processor” API to libpq for better handling of large
results. Traditionally libpq has collected an entire query result
before passing it back to the application. That provides a simple
and transactional API, but it’s pretty inefficient for large result
sets. This patch allows the application to process each row
on-the-fly instead of accumulating the rows into the PGresult.
Error recovery becomes a bit more complex, but often that tradeoff
is well worth making. Kyotaro Horiguchi, reviewed by Marko Kreen
and Tom Lane
– Improve efficiency of dblink by using libpq’s new row processor API.
This patch provides a test case for libpq’s row processor API.
contrib/dblink can deal with very large result sets by dumping them
into a tuplestore (which can spill to disk) — but until now, the
intermediate storage of the query result in a PGresult meant memory
bloat for any large result. Now we use a row processor to convert
the data to tuple form and dump it directly into the tuplestore. A
limitation is that this only works for plain dblink() queries, not
dblink_send_query() followed by dblink_get_result(). In the latter
case we don’t know the desired tuple rowtype soon enough. While
hack solutions to that are possible, a different user-level API
would probably be a better answer. Kyotaro Horiguchi, reviewed by
Marko Kreen and Tom Lane
– Fix plpgsql named-cursor-parameter feature for variable name
conflicts. The parser got confused if a cursor parameter had the
same name as a plpgsql variable. Reported and diagnosed by Yeb
Havinga, though this isn’t exactly his proposed fix. Also, some
mostly-but-not-entirely-cosmetic adjustments to the original
named-cursor-parameter patch, for code readability and better error
– Update obsolete comment. Somebody didn’t bother to fix this comment
while adding foreign table support to the code below it. In
passing, remove the explicit calling-out of relkind letters, which
adds complexity to the comment but doesn’t help in understanding the
– Allow statistics to be collected for foreign tables. ANALYZE now
accepts foreign tables and allows the table’s FDW to control how the
sample rows are collected. (But only manual ANALYZEs will touch
foreign tables, for the moment, since among other things it’s not
very clear how to handle remote permissions checks in an
auto-analyze.) contrib/file_fdw is extended to support this. Etsuro
Fujita, reviewed by Shigeru Hanada, some further tweaking by me.
– Dept of second thoughts: improve the API for AnalyzeForeignTable.
If we make the initially-called function return the table
physical-size estimate, acquire_inherited_sample_rows will be able
to use that to allocate numbers of samples among child tables, when
the day comes that we want to support foreign tables in inheritance
– Fix broken comparetup_datum code. Commit
337b6f5ecf05b21b5e997986884d097d60e4e3d0 contained the entirely
fanciful assumption that it had made comparetup_datum unreachable.
Reported and patched by Takashi Yamamoto. Fix up some not terribly
accurate/useful comments from that commit, too.
– Fix misleading output from gin_desc(). XLOG_GIN_UPDATE_META_PAGE
and XLOG_GIN_DELETE_LISTPAGE records were printed with a list link
field labeled as “blkno”, which was confusing, especially when the
link was empty (InvalidBlockNumber). Print the metapage block
number instead, since that’s what’s actually being updated. We
could include the link values too as a separate field, but not clear
it’s worth the trouble. Back-patch to 8.4 where the dubious code
– Update URL for pgtclng project. Thom Brown
– Remove useless variable to suppress compiler warning.
– Further adjustment of comment about qsort_tuple.
– Fix incorrect make maintainer-clean rule.
– Improve management of “sticky” entries in
contrib/pg_stat_statements. This patch addresses a deficiency in
the previous pg_stat_statements patch. We want to give sticky
entries an initial “usage” factor high enough that they probably
will stick around until their query is completed. However, if the
query never completes (eg it gets an error during execution), the
entry shouldn’t persist indefinitely. Manage this by starting out
with a usage setting equal to the (approximate) median usage value
within the whole hashtable, but decaying the value much more
aggressively than we do for normal entries. Peter Geoghegan
Simon Riggs pushed:
– Add DROP INDEX CONCURRENTLY [IF EXISTS], uses ShareUpdateExclusiveLock
Bruce Momjian pushed:
– Stamp libraries versions for 9.2 (better late than never).
Heikki Linnakangas pushed:
– Do stack-depth checking in all postmaster children. We used to only
initialize the stack base pointer when starting up a regular
backend, not in other processes. In particular, autovacuum workers
can run arbitrary user code, and without stack-depth checking,
infinite recursion in e.g an index expression will bring down the
whole cluster. The comment about PL/Java using set_stack_base() is
not yet true. As the code stands, PL/java still modifies the
stack_base_ptr variable directly. However, it’s been discussed in
the PL/Java mailing list that it should be changed to use the
function, because PL/Java is currently oblivious to the register
stack used on Itanium. There’s another issues with PL/Java, namely
that the stack base pointer it sets is not really the base of the
stack, it could be something close to the bottom of the stack.
That’s a separate issue that might need some further changes to this
code, but that’s a different story. Backpatch to all supported
– set_stack_base() no longer needs to be called in PostgresMain. This
was a thinko in previous commit. Now that stack base pointer is now
set in PostmasterMain and SubPostmasterMain, it doesn’t need to be
set in PostgresMain anymore.
== Rejected Patches (for now) ==
No one was disappointed this week
== Pending Patches ==
Etsuro Fujita and Shigeru HANADA traded patches to implement various
parts of a PostgreSQL FDW.
Gilles Darold sent in some patches to help tell when PostgreSQL is in
Josh Kupershmidt sent in a patch to fix psql’s tab completion for WITH
under some circumstances.
Heikki Linnakangas and Pavel Stehule traded versions of the CHECK
Joachim Wieland sent in two more revisions of the patch to make
pg_dump able to operate in parallel.
Yeb Havinga sent in two revisions of a patch intended to fix an issue
with cursor arguments in named notation.
Zoltan Boszormenyi sent in five revisions of a patch to implement a
framework to simplify and correctly nest multiplexing more than two
timeout sources into the same SIGALRM signal handler.
Robert Haas sent in a patch to fix the SLRU replacement algorithm.
Peter Eisentraut sent in a patch to rename bytea_agg() to
string_agg(), which now covers bytea types.
Peter Geoghegan sent in a patch to do some speedups in
Alvaro Herrera sent in another revision of the patch to add URI
support to libpq, along with some documentation fo the changes.
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