== PostgreSQL Weekly News - April 06 2014 ==

From: David Fetter <david(at)fetter(dot)org>
To: PostgreSQL Announce <pgsql-announce(at)postgresql(dot)org>
Subject: == PostgreSQL Weekly News - April 06 2014 ==
Date: 2014-04-06 23:13:19
Message-ID: 20140406231319.GA22135@fetter.org
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== PostgreSQL Weekly News - April 06 2014 ==

== PostgreSQL Product News ==

PostgreSQL Columnar Store for Analytic Workloads released.

DBD::Pg, the Perl driver for Postgres, has released version 3.1.0:

pgbuildfarm client 4.12 released.

pgCluu 2.0, a Perl program audit PostgreSQL Cluster performance,

pg_extractor 2.0.0, a customizing add-on to pg_dump, released.

Postgres-XC 1.2.1, a write-scalable multi-master symmetric cluster
based on PostgreSQL, released.

Skytools 3.2, a package of tools developed by Skype for replication
and failover including PgQ, a generic queuing framework and Londiste,
a row-based master-slave replication replication system, released:

tds_fdw, a foreign data wrapper for MS-SQL Server and Sybase,
released. Prospective owners wanted.

== PostgreSQL Jobs for April ==


== PostgreSQL Local ==

The Open Data Summit will be held Friday April 11, 2014 in Denver,
Colorado, USA.

PGCon 2014, the world-wide developer conference for PostgreSQL, will
be in Ottawa, Ontario, Canada May 20-24, 2014.

The sixth PGDay Cubano be held on 13 and 14 October 2014 in Habana.

== 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
to pwn(at)arpug(dot)com(dot)ar(dot)

== Applied Patches ==

Heikki Linnakangas pushed:

- Rename GinLogicValue to GinTernaryValue. It's more descriptive.
Also, get rid of the enum, and use #defines instead, per Greg
Stark's suggestion.

- Rewrite the way GIN posting lists are packed on a page, to reduce
WAL volume. Inserting (in retail) into the new 9.4 format GIN
posting tree created much larger WAL records than in 9.3. The
previous strategy to WAL logging was basically to log the whole page
on each change, with the exception of completely unmodified segments
up to the first modified one. That was not too bad when appending to
the end of the page, as only the last segment had to be WAL-logged,
but per Fujii Masao's testing, even that produced 2x the WAL volume
that 9.3 did. The new strategy is to keep track of changes to the
posting lists in a more fine-grained fashion, and also make the
repacking" code smarter to avoid decoding and re-encoding segments

- Fix typo in comment. Amit Langote

- Move SizeOfHeapNewCid next to xl_heap_new_cid struct. They belong
together, but the xl_heap_rewrite_mapping struct was wedged in

- Fix bug in the new B-tree incomplete-split code. Inserting a
downlink to an internal page clears the incomplete-split flag of the
child's left sibling, so the left sibling's LSN also needs to be

- Remove dead check for backup block, replace with Assert. We don't
use backup blocks with GIN vacuum records anymore, the page is
always recreated from scratch.

- Fix bug in the new GIN incomplete-split code. Inserting a downlink
to an internal page clears the incomplete-split flag of the child's
left sibling, so the left sibling's LSN also needs to be updated and
it needs to be marked dirty. The codepath for an insertion got this
right, but the case where the internal node is split because of
inserting the new downlink missed that.

- Avoid palloc in critical section in GiST WAL-logging. Memory
allocation can fail if you run out of memory, and inside a critical
section that will lead to a PANIC. Use conservatively-sized arrays
in stack instead. There was previously no explicit limit on the
number of pages a GiST split can produce, it was only limited by the
number of LWLocks that can be held simultaneously (100 at the
moment). This patch adds an explicit limit of 75 pages. That should
be plenty, a typical split shouldn't produce more than 2-3 page
halves. The bug has been there forever, but only backpatch down to
9.1. The code was changed significantly in 9.1, and it doesn't seem
worth the risk or trouble to adapt this for 9.0 and 8.4.

- Avoid allocations in critical sections. If a palloc in a critical
section fails, it becomes a PANIC.

- Add an Assertion that you don't palloc within a critical section.
This caught a bunch of cases doing that already, which I just fixed
in previous commit. This is the assertion itself. Per Tom Lane's

- In checkpoint, move the check for in-progress xacts out of critical
section. GetVirtualXIDsDelayingChkpt calls palloc, which isn't safe
in a critical section. I thought I covered this case with the
exemption for the checkpointer, but CreateCheckPoint is also called
from the startup process.

- Move multixid allocation out of critical section. It can fail if
you run out of memory. This call was added in 9.3, so backpatch to
9.3 only.

- Fix another palloc in critical section. Also add a regression test
for a GIN index with enough items with the same key, so that a GIN
posting tree gets created. Apparently none of the existing GIN tests
were large enough for that. This code is new, no backpatching

Robert Haas pushed:

- Fix thinko in logical decoding code. Andres Freund

- Count buffers dirtied due to hints in
pgBufferUsage.shared_blks_dirtied. Previously, such buffers weren't
counted, with the possible result that EXPLAIN (BUFFERS) and
pg_stat_statements would understate the true number of blocks
dirtied by an SQL statement. Back-patch to 9.2, where this counter
was introduced. Amit Kapila

- test_decoding: Update .gitignore. Commit
7317d8d961f210c3a6b20972cd605bcd9bffb06e changed the set of things
that need to be ignored, but neglected to update .gitignore.

- Mark FastPathStrongRelationLocks volatile. Otherwise, the compiler
might decide to move modifications to data within this structure
outside the enclosing SpinLockAcquire / SpinLockRelease pair,
leading to shared memory corruption. This may or may not explain a
recent lmgr-related buildfarm failure on prairiedog, but it needs to
be fixed either way.

- Fix some compiler warnings that clang emits with -pedantic. Andres

Tom Lane pushed:

- Doc: improve discussion of reverse+forward host name lookup in
pg_hba.conf. Fix some grammatical issues and make it a bit more

- Fix bugs in manipulation of PgBackendStatus.st_clienthostname.
Initialization of this field was not being done according to the
st_changecount protocol (it has to be done within the changecount
increment range, not outside). And the test to see if the value
should be reported as null was wrong. Noted while perusing uses of
Port.remote_hostname. This was wrong from the introduction of this
code (commit 4a25bc145), so back-patch to 9.1.

- De-anonymize the union in JsonbValue. Needed for strict C89

- Fix assorted issues in client host name lookup. The code for
matching clients to pg_hba.conf lines that specify host names
(instead of IP address ranges) failed to complain if reverse DNS
lookup failed; instead it silently didn't match, so that you might
end up getting a surprising "no pg_hba.conf entry for ..." error, as
seen in bug #9518 from Mike Blackwell. Since we don't want to make
this a fatal error in situations where pg_hba.conf contains a
mixture of host names and IP addresses (clients matching one of the
numeric entries should not have to have rDNS data), remember the
lookup failure and mention it as DETAIL if we get to "no pg_hba.conf
entry". Apply the same approach to forward-DNS lookup failures,
too, rather than treating them as immediate hard errors. Along the
way, fix a couple of bugs that prevented us from detecting an rDNS
lookup error reliably, and make sure that we make only one rDNS
lookup attempt; formerly, if the lookup attempt failed, the code
would try again for each host name entry in pg_hba.conf. Since more
or less the whole point of this design is to ensure there's only one
lookup attempt not one per entry, the latter point represents a
performance bug that seems sufficient justification for
back-patching. Also, adjust src/port/getaddrinfo.c so that it plays
as well as it can with this code. Which is not all that well, since
it does not have actual support for rDNS lookup, but at least it
should return the expected (and required by spec) error codes so
that the main code correctly perceives the lack of functionality as
a lookup failure. It's unlikely that PG is still being used in
production on any machines that require our getaddrinfo.c, so I'm
not excited about working harder than this. To keep the code in the
various branches similar, this includes back-patching commits
c424d0d1052cb4053c8712ac44123f9b9a9aa3f2 and
1997f34db4687e671690ed054c8f30bb501b1168 into 9.2 and earlier.
Back-patch to 9.1 where the facility for hostnames in pg_hba.conf
was introduced.

- Avoid promising that "ADD COLUMN ... DEFAULT NULL" is free. The
system realizes that DEFAULT NULL is dummy in simple cases, but not
if a cast function (such as a length coercion) needs to be applied.
It's dubious that suppressing that function call would be
appropriate, anyway. For the moment, let's just adjust the docs to
say that you should omit the DEFAULT clause if you don't want a
rewrite to happen. Per gripe from Amit Langote.

- Fix documentation about joining pg_locks to other views. The advice
to join to pg_prepared_xacts via the transaction column was not
updated when the transaction column was replaced by
virtualtransaction. Since it's not quite obvious how to do that
join, give an explicit example. For consistency also give an
example for the adjacent case of joining to pg_stat_activity. And
link-ify the view references too, just because we can. Per bug
#9840 from Alexey Bashtanov. Michael Paquier and Tom Lane

- Code review for commit d26888bc4d1e539a82f21382b0000fe5bbf889d9.
Mostly, copy-edit the comments; but also fix it to not reject
domains over arrays.

- Fix non-equivalence of VARIADIC and non-VARIADIC function call
formats. For variadic functions (other than VARIADIC ANY), the
syntaxes foo(x,y,...) and foo(VARIADIC ARRAY[x,y,...]) should be
considered equivalent, since the former is converted to the latter
at parse time. They have indeed been equivalent, in all releases
before 9.3. However, commit 75b39e790 made an ill-considered
decision to record which syntax had been used in FuncExpr nodes, and
then to make equal() test that in checking node equality --- which
caused the syntaxes to not be seen as equivalent by the planner.
This is the underlying cause of bug #9817 from Dmitry Ryabov. It
might seem that a quick fix would be to make equal() disregard
FuncExpr.funcvariadic, but the same commit made that untenable,
because the field actually *is* semantically significant for some
VARIADIC ANY functions. This patch instead adopts the approach of
redefining funcvariadic (and aggvariadic, in HEAD) as meaning that
the last argument is a variadic array, whether it got that way by
parser intervention or was supplied explicitly by the user.
Therefore the value will always be true for non-ANY variadic
functions, restoring the principle of equivalence. (However, the
planner will continue to consider use of VARIADIC as a meaningful
difference for VARIADIC ANY functions, even though some such
functions might disregard it.) In HEAD, this change lets us simplify
the decompilation logic in ruleutils.c, since the
funcvariadic/aggvariadic flag tells directly whether to print
VARIADIC. However, in 9.3 we have to continue to cope with existing
stored rules/views that might contain the previous definition.
Fortunately, this just means no change in ruleutils.c, since its
existing behavior effectively ignores funcvariadic for all cases
other than VARIADIC ANY functions. In HEAD, bump catversion to
reflect the fact that FuncExpr.funcvariadic changed meanings; this
is sort of pro forma, since I don't believe any built-in views are
affected. Unfortunately, this patch doesn't magically fix
everything for affected 9.3 users. After installing 9.3.5, they
might need to recreate their rules/views/indexes containing variadic
function calls in order to get everything consistent with the new
definition. As in the cited bug, the symptom of a problem would be
failure to use a nominally matching index that has a variadic
function call in its definition. We'll need to mention this in the
9.3.5 release notes.

- Fix bogus time printout in walreceiver's debug log messages. The
displayed sendtime and receipttime were always exactly equal,
because somebody forgot that timestamptz_to_str returns a static
buffer (thereby simplifying life for most callers, at the cost of
complicating it for those who need two results concurrently). Apply
the same pstrdup solution used by the other call sites with this
issue. Back-patch to 9.2 where the faulty code was introduced. Per
bug #9849 from Haruka Takatsuka, though this is not exactly his
patch. Possibly we should change timestamptz_to_str's API, but I
wouldn't want to do so in the back branches.

- Make sure -D is an absolute path when starting server on Windows.
This is needed because Windows services may get started with a
different current directory than where pg_ctl is executed. We want
relative -D paths to be interpreted relative to pg_ctl's CWD,
similarly to what happens on other platforms. In support of this,
move the backend's make_absolute_path() function into
src/port/path.c (where it probably should have been long since) and
get rid of the rather inferior version in pg_regress. Kumar Rajeev
Rastogi, reviewed by MauMau

- Preserve errno across free(). Dept. of second thoughts: free()
isn't guaranteed not to change errno. Make sure we report the right
error if getcwd() fails.

- Allow "-C variable" and "--describe-config" even to root users.
There's no really compelling reason to refuse to do these read-only,
non-server-starting options as root, and there's at least one good
reason to allow -C: pg_ctl uses -C to find out the true data
directory location when pointed at a config-only directory. On
Windows, this is done before dropping administrator privileges,
which means that pg_ctl fails for administrators if and only if a
config-only layout is used. Since the root-privilege check is done
so early in startup, it's a bit awkward to check for these switches.
Make the somewhat arbitrary decision that we'll only skip the root
check if -C is the first switch. This is not just to make the code
a bit simpler: it also guarantees that we can't misinterpret a
--boot mode switch. (While AuxiliaryProcessMain doesn't currently
recognize any such switch, it might have one in the future.) This
is no particular problem for pg_ctl, and since the whole behavior is
undocumented anyhow, it's not a documentation issue either.
(--describe-config only works as the first switch anyway, so this is
no restriction for that case either.) Back-patch to 9.2 where pg_ctl
first began to use -C. MauMau, heavily edited by me

- Fix tablespace creation WAL replay to work on Windows. The code
segment that removes the old symlink (if present) wasn't clued into
the fact that on Windows, symlinks are junction points which have to
be removed with rmdir(). Backpatch to 9.0, where the failing code
was introduced. MauMau, reviewed by Muhammad Asif Naeem and Amit

- ecpg/ecpglib must build the src/port files it uses with -DFRONTEND.
Remarkably, this hasn't been noticed before, though it surely should
have been happening since around the fall of the Byzantine empire.
Commit 438b529604 changed path.c to depend on FRONTEND, and that
exposed the omission, per buildfarm reports. I'm suspicious that
some other subdirectories are missing this too, but this one change
is enough to make ecpg tests pass for me.

- Fix processing of PGC_BACKEND GUC parameters on Windows.
EXEC_BACKEND builds (i.e., Windows) failed to absorb values of
PGC_BACKEND parameters if they'd been changed post-startup via the
config file. This for example prevented log_connections from
working if it were turned on post-startup. The mechanism for
handling this case has always been a bit of a kluge, and it wasn't
revisited when we implemented EXEC_BACKEND. While in a normal
forking environment new backends will inherit the postmaster's value
of such settings, EXEC_BACKEND backends have to read the settings
from the CONFIG_EXEC_PARAMS file, and they were mistakenly rejecting
them. So this case has always been broken in the Windows port; so
back-patch to all supported branches. Amit Kapila

- Block signals earlier during postmaster startup. Formerly, we set
up the postmaster's signal handling only when we were about to start
launching subprocesses. This is a bad idea though, as it means that
for example a SIGINT arriving before that will kill the postmaster
instantly, perhaps leaving lockfiles, socket files, shared memory,
etc laying about. We'd rather that such a signal caused orderly
postmaster termination including releasing of those resources. A
simple fix is to move the PostmasterMain stanza that initializes
signal handling to an earlier point, before we've created any such
resources. Then, an early-arriving signal will be blocked until
we're ready to deal with it in the usual way. (The only part that
really needs to be moved up is blocking of signals, but it seems
best to keep the signal handler installation calls together with
that; for one thing this ensures the kernel won't drop any signals
we wished to get. The handlers won't get invoked in any case until
we unblock signals in ServerLoop.) Per a report from MauMau. He
proposed changing the way "pg_ctl stop" works to deal with this, but
that'd just be masking one symptom not fixing the core issue. It's
been like this since forever, so back-patch to all supported

- Improve contrib/pg_trgm's heuristics for regexp index searches.
When extracting trigrams from a regular expression for search of a
GIN or GIST trigram index, it's useful to penalize (preferentially
discard) trigrams that contain whitespace, since those are typically
far more common in the index than trigrams not containing
whitespace. Of course, this should only be a preference not a hard
rule, since we might otherwise end up with no trigrams to search
for. The previous coding tended to produce fairly inefficient
trigram search sets for anchored regexp patterns, as reported by
Erik Rijkers. This patch penalizes whitespace-containing trigrams,
and also reduces the target number of extracted trigrams, since
experience suggests that the original coding tended to select too
many trigrams to search for. Alexander Korotkov, reviewed by Tom

Simon Riggs pushed:

- Reduce lock levels of some ALTER TABLE cmds: VALIDATE CONSTRAINT
COLUMN SET (), and ALTER COLUMN RESET (). All other sub-commands
use AccessExclusiveLock. Simon Riggs and Noah Misch. Reviews by
Robert Haas and Andres Freund

- Isolation test files for ALTER TABLE patch

- Extra warnings and errors for PL/pgSQL. Infrastructure to allow
plpgsql.extra_warnings plpgsql.extra_errors Initial extra checks
only for shadowed_variables Marko Tiikkaja and Petr Jelinek Reviewed
by Simon Riggs and Pavel Stěhule

== Rejected Patches (for now) ==

No one was disappointed this week :-)

== Pending Patches ==

Michael Paquier sent in another revision of a patch to add a new
parameter RollbackError to control rollback behavior on error.

Edward Behn sent in a patch to allow returning array of composites
from PL/Python.

Etsuro Fujita sent in two more revisions of a patch to allow foreign
tables to be part of table inheritance hierarchies.

Yugo Nagata and Robert Haas traded patches to add to_regclass and

Peter Geoghegan sent in another revision of a patch to add a B-Tree
support function.

Bruce Momjian sent in a patch to fix an issue with socket handling on

Fabien COELHO sent in another revision of a patch to add a Gaussian
distribution option to pgbench.

Kumar Rajeev Rastogi sent in a patch to document the usage of CREATE
DATABASE with template specified.

Adrian Vondendriesch sent in two more revisions of a patch to provide
a allback_application_name in contrib/pgbench, oid2name, and dblink.

Ashutosh Bapat sent in a patch to fix an infelicity in how ECPG
handles types.

Michael Paquier sent in a patch to include replication slot data in
base backups.

Florian Pflug and Dean Rasheed traded patches to add inverse
transition functions for aggregates.

Abhijit Menon-Sen sent in a patch to add a fastbloat module.

Robert Haas sent in a draft patch to get rid of the dynamic shared
memory state file.

Heikki Linnakangas sent in another revision of a patch to change the
WAL format and API.

Kumar Rajeev Rastogi sent in a patch to fix an issue where CREATE
TABLE failed to fail on invalid syntax.

Emre Hasegeli sent in another revision of a patch to add GiST indexing
support for inet data types.

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