== PostgreSQL Weekly News – April 15 2012 ==

== PostgreSQL Weekly News – April 15 2012 ==

The second meeting of Arizona PostgreSQL Users Group at 6:30 PM on
Wednesday, April 25, and will start with pizza and refreshments. You
can join the mailing list, and RSVP at:

== PostgreSQL Product News ==

EnterpriseDB Postgres Enterprise Manager v2.1 released.

MyJSQLView Version 3.34 Released.

Postgres-XC 1.0beta1, a synchronous multi-master replication system
based on 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

Submit news and announcements by Sunday at 3:00pm Pacific time.
Please send English language ones to david@fetter.org, German language
to pwn@pgug.de, Italian language to pwn@itpug.org. Spanish language
to pwn@arpug.com.ar.

== Reviews ==

== Applied Patches ==

Heikki Linnakangas pushed:

- Remove link to ODBCng project from the docs. Thom Browne pointed
out that the URL was out of date, and Devrim GÜNDÜZ pointed out that
the project isn’t maintained anymore.

- Fix typos in docs, some words were doubled. Thom Brown

- Point the URL to PL/py directly to the page about the procedural
language. It used to point to a top-level page that contains
client-side tools as well. It was hard to find the procedural
language there.

Tom Lane pushed:

- Save a few cycles while creating “sticky” entries in
pg_stat_statements. There’s no need to sit there and increment the
stats when we know all the increments would be zero anyway. The
actual additions might not be very expensive, but skipping
acquisition of the spinlock seems like a good thing. Pushing the
logic about initialization of the usage count down into
entry_alloc() allows us to do that while making the code actually
simpler, not more complex. Expansion on a suggestion by Peter

- Don’t bother copying empty support arrays in a zero-column
MergeJoin. The case could not arise when this code was originally
written, but it can now (since we made zero-column MergeJoins work
for the benefit of FULL JOIN ON TRUE). I don’t think there is any
actual bug here, but we might as well treat it consistently with
other uses of COPY_POINTER_FIELD(). Per comment from Ashutosh

- Fix an Assert that turns out to be reachable after all.
estimate_num_groups() gets unhappy with create table empty(); select
* from empty except select * from empty e2; I can’t see any actual
use-case for such a query (and the table is illegal per SQL spec),
but it seems like a good idea that it not cause an assert failure.

- Adjust various references to GEQO being non-deterministic. It’s
still non-deterministic in some sense … but given fixed settings
and identical planning problems, it will now always choose the same
plan, so we probably shouldn’t tar it with that brush. Per bug
#6565 from Guillaume Cottenceau. Back-patch to 9.0 where the
behavior was fixed.

- Measure epoch of timestamp-without-time-zone from local not UTC
midnight. This patch reverts commit
191ef2b407f065544ceed5700e42400857d9270f and thereby restores the
pre-7.3 behavior of EXTRACT(EPOCH FROM timestamp-without-tz). Per
discussion, the more recent behavior was misguided on a couple of
grounds: it makes it hard to get a non-timezone-aware epoch value
for a timestamp, and it makes this one case dependent on the value
of the timezone GUC, which is incompatible with having
timestamp_part() labeled as immutable. The other behavior is still
available (in all releases) by explicitly casting the timestamp to
timestamp with time zone before applying EXTRACT. This will need to
be called out as an incompatible change in the 9.2 release notes.
Although having mutable behavior in a function marked immutable is
clearly a bug, we’re not going to back-patch such a change.

- Make pg_tablespace_location(0) return the database’s default
tablespace. This definition is convenient when applying the
function to the reltablespace column of pg_class, since that’s what
zero means there; and it doesn’t interfere with any other plausible
use of the function. Per gripe from Bruce Momjian.

- Silently ignore any nonexistent schemas that are listed in
search_path. Previously we attempted to throw an error or at least
warning for missing schemas, but this was done inconsistently
because of implementation restrictions (in many cases, GUC settings
are applied outside transactions so that we can’t do system catalog
lookups). Furthermore, there were exceptions to the rule even in
the beginning, and we’d been poking more and more holes in it as
time went on, because it turns out that there are lots of use-cases
for having some irrelevant items in a common search_path value. It
seems better to just adopt a philosophy similar to what’s always
been done with Unix PATH settings, wherein nonexistent or unreadable
directories are silently ignored. This commit also fixes the
documentation to point out that schemas for which the user lacks
USAGE privilege are silently ignored. That’s always been true but
was previously not documented. This is mostly in response to Robert
Haas’ complaint that 9.1 started to throw errors or warnings for
missing schemas in cases where prior releases had not. We won’t
adopt such a significant behavioral change in a back branch, so
something different will be needed in 9.1.

- Fix cost estimation for indexscan filter conditions. cost_index’s
method for estimating per-tuple costs of evaluating filter
conditions (a/k/a qpquals) was completely wrong in the presence of
derived indexable conditions, such as range conditions derived from
a LIKE clause. This was largely masked in common cases as a result
of all simple operator clauses having about the same costs, but it
could show up in a big way when dealing with functional indexes
containing expensive functions, as seen for example in bug #6579
from Istvan Endredy. Rejigger the calculation to give sane answers
when the indexquals aren’t a subset of the baserestrictinfo list.
As a side benefit, we now do the calculation properly for cases
involving join clauses (ie, parameterized indexscans), which we
always overestimated before. There are still cases where this is an
oversimplification, such as clauses that can be dropped because they
are implied by a partial index’s predicate. But we’ve never
accounted for that in cost estimates before, and I’m not convinced
it’s worth the cycles to try to do so.

- Assorted spelling corrections. Thom Brown

- Remove the “last ditch” code path in join_search_one_level(). So
far as I can tell, it is no longer possible for this heuristic to do
anything useful, because the new weaker definition of
have_relevant_joinclause means that any relation with a joinclause
must be considered joinable to at least one other relation. It
would still be possible for the code block to be entered, for
example if there are join order restrictions that prevent any join
of the current level from being formed; but in that case it’s just a
waste of cycles to attempt to form cartesian joins, since the
restrictions will still apply. Furthermore, IMO the existence of
this code path can mask bugs elsewhere; we would have noticed the
problem with cartesian joins a lot sooner if this code hadn’t
compensated for it in the simplest case. Accordingly, let’s remove
it and see what happens. I’m committing this separately from the
prerequisite changes in have_relevant_joinclause, just to make the
question easier to revisit if there is some fault in my logic.

- Weaken the planner’s tests for relevant joinclauses. We should be
willing to cross-join two small relations if that allows us to use
an inner indexscan on a large relation (that is, the potential
indexqual for the large table requires both smaller relations).
This worked in simple cases but fell apart as soon as there was a
join clause to a fourth relation, because the existence of any
two-relation join clause caused the planner to not consider
clauseless joins between other base relations. The added regression
test shows an example case adapted from a recent complaint from
Benoit Delbosc. Adjust have_relevant_joinclause,
have_relevant_eclass_joinclause, and has_relevant_eclass_joinclause
to consider that a join clause mentioning three or more relations is
sufficient grounds for joining any subset of those relations, even
if we have to do so via a cartesian join. Since such clauses are
relatively uncommon, this shouldn’t affect planning speed on typical
queries; in fact it should help a bit, because the latter two
functions in particular get significantly simpler. Although this is
arguably a bug fix, I’m not going to risk back-patching it, since it
might have currently-unforeseen consequences.

Bruce Momjian pushed:

- Remove documentation mention of pglesslog, which was added in 2009
because there was only a beta for 9.0 and it does not compile on

- Update documentation to more clearly label the streaming replication

- Re-add documentation recommendation to use gzip/gunzip for archive
file storage.

- Fix pg_upgrade to properly upgrade a table that is stored in the
cluster default tablespace, but part of a database that is in a
user-defined tablespace. Caused “file not found” error during
upgrade. Per bug report from Ants Aasma. Backpatch to 9.1 and 9.0.

Peter Eisentraut pushed:

- psql: Improve tab completion of WITH. Only match when WITH is the
first word, as WITH may appear in many other contexts. Josh

- NLS: Initialize Project-Id-Version field by xgettext. Since
xgettext provides options to do this now, we might as well use them.

- Consistently quote encoding and locale names in messages

- Rename bytea_agg to string_agg and add delimiter argument. Per
mailing list discussion, we would like to keep the bytea functions
parallel to the text functions, so rename bytea_agg to string_agg,
which already exists for text. Also, to satisfy the rule that we
don’t want aggregate functions of the same name with a different
number of arguments, add a delimiter argument, just like string_agg
for text already has.

- Fix typo. Etsuro Fujita

- Document that VALUES can be used in WITH

- Update contrib/README. Remove lots of outdated information that is
duplicated by the better-maintained SGML documentation. In
particular, remove the outdated listing of contrib modules. Update
the installation instructions to mention CREATE EXTENSION, but don’t
go into too much detail.

- PL/Python: Fix crash when colnames() etc. called without result set.
The result object methods colnames() etc. would crash when called
after a command that did not produce a result set. Now they throw
an exception. discovery and initial patch by Jean-Baptiste Quenot

Alvaro Herrera pushed:

- Accept postgres:// URIs in libpq connection functions. postgres://
URIs are an attempt to “stop the bleeding” in this general area that
has been said to occur due to external projects adopting their own
syntaxes. The syntaxes supported by this patch:
should be enough to cover most interesting cases without having to
resort to “param=value” pairs, but those are provided for the cases
that need them regardless. libpq documentation has been shuffled
around a bit, to avoid stuffing all the format details into the
PQconnectdbParams description, which was already a bit overwhelming.
The list of keywords has moved to its own subsection, and the
details on the URI format live in another subsection. This includes
a simple test program, as requested in discussion, to ensure that
interesting corner cases continue to work appropriately in the
future. Author: Alexander Shulgin Some tweaking by Álvaro Herrera,
Greg Smith, Daniel Farina, Peter Eisentraut Reviewed by Robert Haas,
Alexey Klyukin (offlist), Heikki Linnakangas,Marko Kreen, and others
Oh, it also supports postgresql:// but that’s probably just an

Robert Haas pushed:

- Update lazy_scan_heap header comment. The previous comment
described how things worked in PostgreSQL 8.2 and prior.

- Fix typo in comment.

- Grammar corrections. Christoph Berg

- Add Peter Geoghegan as additional author of pg_stat_statements.

- pg_size_pretty(numeric). The output of the new
pg_xlog_location_diff function is of type numeric, since it could
theoretically overflow an int8 due to signedness; this provides a
convenient way to format such values. Fujii Masao, with some
beautification by me.

- Rename synchronous_commit=’write’ to ‘remote_write’. Fujii Masao,
per discussion on pgsql-hackers

Tatsuo Ishii pushed:

- Add description of long options for ‘-c’, ‘-D’, ‘-l’ and ‘-s’. Per
discussion of hackers list on 2012/3/10 “missing description initdb

- Add missing descriptions about ‘–timeout’ and ‘–mode’ to help
message. They are already implemented in the source code.
Suggestions about the message formatting from Tom Lane.

== Rejected Patches (for now) ==

Etsuro Fujita’s patch to fix a typo in a comment.

== Pending Patches ==

Vikash S. sent in a patch intended to allow psql to take multiple -f
(file) arguments on the command line.

Robert Haas sent in another revision of the patch implementing

Robert Haas sent in another revision of a patch to fix a bug in
fastpath locking.

Zoltan Boszormenyi sent in another revision of the patch for ECPG
FETCH readahead.

Josh Kupershmidt sent in another revision of the patch to fix psql tab
completion in the WITH case of CREATE/ALTER USER/ROLE.

Zoltan Boszormenyi sent in new versions of two patches: timeout
framework and lock timeout.

Nikhil Sontakke sent in a patch implementing CHECK ONLY in

Heikki Linnakangas sent in a patch to allow compiling PL/pgsql-related
items as EXTENSIONs.

Robert Haas sent in several patches to test different scenarios for
memory usage during sorting.

Etsuro Fujita sent in a patch to add some validating machinery to
FDWs and used same to check NULLness in the file_fdw.

Heikki Linnakangas sent in a patch to ensure that the right domain is
used in errcontext() calls.

Tatsuo Ishii sent in a patch ensuring that pg_ctl –help actually
documents all options the code makes available.

Comments are closed.