== PostgreSQL Weekly News – August 12 2012 ==
== PostgreSQL Weekly News – August 12 2012 ==
== PostgreSQL Jobs for August ==
== PostgreSQL Local ==
PostgreSQL Session will be held on October 4th, 2012, in Paris,
France. More information at:
PostgreSQL Conference Europe 2012 will be in Prague, Czech Republic
on October 23-26. The call for papers is open.
PostgreSQL Day Argentina 2012 will be held on November 13th in Bernal,
Buenos Aires, at the National University of Quilmes. It will cover
topics for PostgreSQL users, developers and contributors, as well as
decision and policy makers. For more information about the
conference, please see the website at
== PostgreSQL in the News ==
Planet PostgreSQL: http://planet.postgresql.org/
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== Applied Patches ==
Simon Riggs pushed:
– fsync backup_label after pg_start_backup(). Dave Kerr
– Fix minor bug in XLogFileRead() that accidentally worked. Cascading
replication copied the incoming file into pg_xlog but didn’t set
path correctly, so the first attempt to open file failed causing it
to loop around and look for file in pg_xlog. So the earlier coding
worked, but accidentally rather than by design. Spotted by Fujii
Masao, fix by Fujii Masao and Simon Riggs
– Doc correction to point out that 9.2+ can overwrite pg_xlog files.
Noted by Noah Misch, patch by Fujii Masao
– Force archive_status of .done for xlogs created by
dearchival/replication. This prevents spurious attempts to archive
xlog files after promotion of standby, a bug introduced by cascading
replication patch in 9.2. Fujii Masao, simplified and extended to
cover streaming by Simon Riggs
– Ensure all replication message info is available and correct via
– Turn off WalSender keepalives by default, users can enable if
Alvaro Herrera pushed:
– Fix redundant wording
– Fix typo in comment
Bruce Momjian pushed:
– Fix pg_upgrade file share violation on Windows created by the commit
4741e9afb93f0d769655b2d18c2b73b86f281010. This was done by adding
an optional second log file parameter to exec_prog(), and closing
and reopening the log file between system() calls. Backpatch to
– Fix to_char(), to_date(), and to_timestamp() to handle negative/BC
century specifications just like positive/AD centuries. Previously
the behavior was either wrong or inconsistent with positive/AD
handling. Centuries without years now always assume the first year
of the century, which is now documented.
– Add additional C comments for to_date/to_char() fixes.
– Fix pgtest to return proper error code based on ‘make’ return code.
– Adjust pgtest coding to be less complex.
– Prevent pg_upgrade from crashing if it can’t write to the current
directory. Backpatch to 9.2.
Robert Haas pushed:
– Fix memory leaks in event trigger code. Spotted by Jeff Davis.
– Fix cache flush hazard in event trigger cache. Bug spotted by Jeff
Davis using -DCLOBBER_CACHE_ALWAYS.
– Make psql -1 < file behave as expected. Previously, the -1 option
was silently ignored. Also, emit an error if -1 is used in a
context where it won’t be respected, to avoid user confusion.
Original patch by Fabien COELHO, but this version is quite different
from the original submission.
Tom Lane pushed:
– Tweak new Perl pgindent for compatibility with middle-aged Perls.
We seem to have a rough policy that our Perl scripts should work
with Perl 5.8, so make this one do so. Main change is to not use
the newfangled h character class in regexes; “[ t]” is a
– Implement SQL-standard LATERAL subqueries. This patch implements
the standard syntax of LATERAL attached to a sub-SELECT in FROM, and
also allows LATERAL attached to a function in FROM, since
set-returning function calls are expected to be one of the principal
use-cases. The main change here is a rewrite of the mechanism for
keeping track of which relations are visible for column references
while the FROM clause is being scanned. The parser “namespace”
lists are no longer lists of bare RTEs, but are lists of
ParseNamespaceItem structs, which carry an RTE pointer as well as
some visibility-controlling flags. Aside from supporting LATERAL
correctly, this lets us get rid of the ancient hacks that required
rechecking subqueries and JOIN/ON and function-in-FROM expressions
for invalid references after they were initially parsed. Invalid
column references are now always correctly detected on sight. In
passing, remove assorted parser error checks that are now dead code
by virtue of our having gotten rid of add_missing_from, as well as
some comments that are obsolete for the same reason. (It was mainly
add_missing_from that caused so much fudging here in the first
place.) The planner support for this feature is very minimal, and
will be improved in future patches. It works well enough for
testing purposes, though. catversion bump forced due to new field
– Fix TwoPhaseGetDummyBackendId(). This was broken in commit
ed0b409d22346b1b027a4c2099ca66984d94b6dd, which revised the
GlobalTransactionData struct to not include the associated PGPROC as
its first member, but overlooked one place where a cast was used in
reliance on that equivalence. The most effective way of fixing this
seems to be to create a new function that looks up the
GlobalTransactionData struct given the XID, and make both
TwoPhaseGetDummyBackendId and TwoPhaseGetDummyProc rely on that.
Per report from Robert Ross.
– Update isolation tests’ README file. The directions explaining
about running the prepared-transactions test were not updated in
– Merge parser’s p_relnamespace and p_varnamespace lists into a single
list. Now that we are storing structs in these lists, the
distinction between the two lists can be represented with a couple
of extra flags while using only a single list. This simplifies the
code and should save a little bit of palloc traffic, since the
majority of RTEs are represented in both lists anyway.
– Centralize the logic for detecting misplaced aggregates, window
funcs, etc. Formerly we relied on checking after-the-fact to see if
an expression contained aggregates, window functions, or sub-selects
when it shouldn’t. This is grotty, easily forgotten (indeed, we had
forgotten to teach DefineIndex about rejecting window functions),
and none too efficient since it requires extra traversals of the
parse tree. To improve matters, define an enum type that classifies
all SQL sub-expressions, store it in ParseState to show what kind of
expression we are currently parsing, and make
transformAggregateCall, transformWindowFuncCall, and
transformSubLink check the expression type and throw error if the
type indicates the construct is disallowed. This allows removal of
a large number of ad-hoc checks scattered around the code base. The
enum type is sufficiently fine-grained that we can still produce
error messages of at least the same specificity as before. Bringing
these error checks together revealed that we’d been none too
consistent about phrasing of the error messages, so standardize the
wording a bit. Also, rewrite checking of aggregate arguments so
that it requires only one traversal of the arguments, rather than up
to three as before. In passing, clean up some more comments left
over from add_missing_from support, and annotate some tests that I
think are dead code now that that’s gone. (I didn’t risk actually
removing said dead code, though.)
– Update overlooked comment.
– Support having multiple Unix-domain sockets per postmaster. Replace
unix_socket_directory with unix_socket_directories, which is a list
of socket directories, and adjust postmaster’s code to allow zero or
more Unix-domain sockets to be created. This is mostly a
straightforward change, but since the Unix sockets ought to be
created after the TCP/IP sockets for safety reasons (better chance
of detecting a port number conflict), AddToDataDirLockFile needs to
be fixed to support out-of-order updates of data directory lockfile
lines. That’s a change that had been foreseen to be necessary
someday anyway. Honza Horak, reviewed and revised by Tom Lane
– Fix dependencies generated during ALTER TABLE ADD CONSTRAINT USING
INDEX. This command generated new pg_depend entries linking the
index to the constraint and the constraint to the table, which match
the entries made when a unique or primary key constraint is built de
novo. However, it did not bother to get rid of the entries linking
the index directly to the table. We had considered the issue when
the ADD CONSTRAINT USING INDEX patch was written, and concluded that
we didn’t need to get rid of the extra entries. But this is wrong:
ALTER COLUMN TYPE wasn’t expecting such redundant dependencies to
exist, as reported by Hubert Depesz Lubaczewski. On reflection it
seems rather likely to break other things as well, since there are
many bits of code that crawl pg_depend for one purpose or another,
and most of them are pretty naive about what relationships they’re
expecting to find. Fortunately it’s not that hard to get rid of the
extra dependency entries, so let’s do that. Back-patch to 9.1,
where ALTER TABLE ADD CONSTRAINT USING INDEX was added.
– Add link from COPY ref page to psql copy. Jeff Janes
– Fix some issues with LATERAL(SELECT UNION ALL SELECT). The LATERAL
marking has to be propagated down to the UNION leaf queries when we
pull them up. Also, fix the formerly stubbed-off
set_append_rel_pathlist(). It does already have enough smarts to
cope with making a parameterized Append path at need; it just has to
not assume that there *must* be an unparameterized path.
– More fixes for planner’s handling of LATERAL. Re-allow subquery
pullup for LATERAL subqueries, except when the subquery is below an
outer join and contains lateral references to relations outside that
outer join. If we pull up in such a case, we risk introducing
lateral cross-references into outer joins’ ON quals, which is
something the code is entirely unprepared to cope with right now;
and I’m not sure it’ll ever be worth coping with. Support lateral
refs in VALUES (this seems to be the only additional path type that
needs such support as a consequence of re-allowing subquery pullup).
Put in a slightly hacky fix for joinpath.c’s refusal to consider
parameterized join paths even when there cannot be any
unparameterized ones. This was causing “could not devise a query
plan for the given query” failures in queries involving more than
two FROM items. Put in an even more hacky fix for
distribute_qual_to_rels() being unhappy with join quals that contain
references to rels outside their syntactic scope; which is to say,
disable that test altogether. Need to think about how to preserve
some sort of debugging cross-check here, while not expending more
cycles than befits a debugging cross-check.
Magnus Hagander pushed:
– Fix upper limit of superuser_reserved_connections, add limit for
wal_senders. Should be limited to the maximum number of connections
excluding autovacuum workers, not including. Add similar check for
max_wal_senders, which should never be higher than max_connections.
== Rejected Patches (for now) ==
No one was disappointed this week
== Pending Patches ==
Pavel Stehule sent in a patch to allow pretty-printing queries.
Alexander Korotkov sent in another revision of the patch to make
SP-GiST for ranges more efficient using 2-d mapping and quad-tree.
Pavel Stehule sent in another revision of the patch to allow assigning
a single-row query’s target list to a corresponding list of psql
variables using a new command gset.
Fujii Masao sent in a patch to fix a bug in pg_trgm.
Jeff Davis sent in another revision of the patch to add 16-bit
checksums to data pages.
Alexander Korotkov sent in two more revisions of a patch to improve
statistics and selectivity estimation for ranges.
Craig Ringer sent in a patch to implement value_to_json for
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