== PostgreSQL Weekly News - March 29 2015 ==

== PostgreSQL Weekly News - March 29 2015 ==

pgDay Paris 2015 will be held in Paris, France, at the headquarters of
"La Poste", on April 21, 2015. Registration is open.
http://pgday.paris/

== PostgreSQL Product News ==

BDR 0.9.0, a replication system based on logical WALs, released.
http://bdr-project.org/docs/0.9.0/release-0.9.0.html

CitusDB 4.0, a hybrid transaction/analytical processing platform on
PostgreSQL, released.
https://www.citusdata.com/blog/20-sumedh/140-citusdb4-0-release-notes

Vitesse DB, a PostgreSQL-based OLAP product which adds LLVM JIT, parallel
query execution and a column store, released.
http://vitessedata.com/

== PostgreSQL Jobs for March ==

http://archives.postgresql.org/pgsql-jobs/2015-03/threads.php

== PostgreSQL Local ==

The CfP for the second Swiss Postgres Conference, to be held June
25-26, 2015 at HSR Rapperswil, is open until April 1.
http://www.postgres-conference.ch/cfp/

The constituent assembly of the Swiss PostgreSQL
Users Group (SwissPUG) will be Friday, April 10, 2015
http://www.swisspug.org

India PostgreSQL UserGroup will hold a PGday in Bengaluru, Karnataka,
India on April 11, 2015. RSVP at
http://www.meetup.com/India-PUG/events/220553997/

There is a Postgres track in a database technology conference(DTCC) in
April 18, 2015 in Beijing, China.
http://dtcc.it168.com/list_jiabin.html

pgDay Paris will be held in Paris France on April 21, 2015.
http://pgday.paris/

PGCon 2015 is June 16-20 in Ottawa, Canada.
http://www.pgcon.org/2015/

PGDay UK, Conference will be taking place on 7th July 2015 – it is aimed at
the UK PostgreSQL Community. The CfP is open until 13 April 2015.
http://www.postgresqlusergroup.org.uk

The Call For Papers for PostgresOpen 2015, being held in Dallas, Texas
from September 16th to 18th, is now open.
http://2015.postgresopen.org/callforpapers/

== 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 ==

Robert Haas pushed:

- Remove ill-advised pre-check for DSM segment exhaustion.
dsm_control->nitems never decreases, so this is testing whether the
server has *ever* run out of DSM segments, not whether it is
*currently* out of DSM segments. Reported off-list by Amit Kapila.
http://git.postgresql.org/pg/commitdiff/372b97097e8c9a67326e99a07da30ab44f6f822a

Andres Freund pushed:

- Fix copy & paste error in 4f1b890b137. Due to the bug delayed
standbys would not delay when applying prepared transactions.
Discussion:
CAB7nPqT6BO1cCn+sAyDByBxA4EKZNAiPi2mFJ=ANeZmnmewRyg(at)mail(dot)gmail(dot)com
Michael Paquier via Coverity.
http://git.postgresql.org/pg/commitdiff/a1105c3dd44c1fb76eb62a708f0421f21b9dde9b

- Don't delay replication for less than recovery_min_apply_delay's
resolution. Recovery delays are implemented by waiting on a latch,
and latches take milliseconds as a parameter. The required amount of
waiting was computed using microsecond resolution though and the
wait loop's abort condition was checking the delay in microseconds
as well. This could lead to short spurts of busy looping when the
overall wait time was below a millisecond, but above 0 microseconds.
Instead just formulate the wait loop's abort condition in
millisecond granularity as well. Given that that's
recovery_min_apply_delay resolution, it seems harmless to not wait
for less than a millisecond. Backpatch to 9.4 where
recovery_min_apply_delay was introduced. Discussion:
20150323141819(dot)GH26995(at)alap3(dot)anarazel(dot)de
http://git.postgresql.org/pg/commitdiff/87cec51d3ad1107f6f224ed7d773e70c8896e4c0

- Centralize definition of integer limits. Several submitted and even
committed patches have run into the problem that C89, our baseline,
does not provide minimum/maximum values for various integer
datatypes. C99's stdint.h does, but we can't rely on it. Several
parts of the code defined limits locally, so instead centralize the
definitions to c.h. This patch also changes the more obvious usages
of literal limit values; there's more places that could be changed,
but it's less clear whether it's beneficial to change those.
Author: Andrew Gierth Discussion:
87619tc5wc(dot)fsf(at)news-spur(dot)riddles(dot)org(dot)uk
http://git.postgresql.org/pg/commitdiff/83ff1618bc9d4e530d3ef2a668a71326784a753c

Heikki Linnakangas pushed:

- Add pg_rewind, for re-synchronizing a master server after failback.
Earlier versions of this tool were available (and still are) on
github. Thanks to Michael Paquier, Alvaro Herrera, Peter
Eisentraut, Amit Kapila, and Satoshi Nagayasu for review.
http://git.postgresql.org/pg/commitdiff/61081e75c6741024f7717ade0450090590e96c85

- Try to fix MSVC build of pg_rewind. It worked in my Windows VM with
VS2013, but buildfarm animal mastodon, running MSVC 2005, was not
happy. Amit Kapila also reported a similar error earlier in his
environment. Let's see if this helps.
http://git.postgresql.org/pg/commitdiff/4babae1a8607ad445cbe761da7f46bb90b156287

- Minor cleanup of GiST code, for readability. Remove the
gistcentryinit function, inlining the relevant part of it into the
only caller.
http://git.postgresql.org/pg/commitdiff/8fa393a6d739796d9f06a7fba91d7e1d0c354879

- Add support for index-only scans in GiST. This adds a new GiST
opclass method, 'fetch', which is used to reconstruct the original
Datum from the value stored in the index. Also, the 'canreturn'
index AM interface function gains a new 'attno' argument. That makes
it possible to use index-only scans on a multi-column index where
some of the opclasses support index-only scans but some do not.
This patch adds support in the box and point opclasses. Other
opclasses can added later as follow-on patches (btree_gist would be
particularly interesting). Anastasia Lubennikova, with additional
fixes and modifications by me.
http://git.postgresql.org/pg/commitdiff/d04c8ed9044eccebce043143a930617e3998c005

- Fix GiST index-only scans for opclasses with different storage type.
We cannot use the index's tuple descriptor directly to describe the
index tuples returned in an index-only scan. That's because the
index might use a different datatype for the values stored on disk
than the type originally indexed. As long as they were both
pass-by-ref, it worked, but will not work for pass-by-value types of
different sizes. I noticed this as a crash when I started hacking a
patch to add fetch methods to btree_gist.
http://git.postgresql.org/pg/commitdiff/55b59eda13a742f8af913734e22ecc8a21754414

- Minor refactoring of btree_gist code. The gbt_var_key_copy function
was doing two different things depending on the boolean argument.
Seems cleaner to have two separate functions. Remove unused
argument from gbt_num_compress.
http://git.postgresql.org/pg/commitdiff/8816af65e4f8285d3ef73158b09490099921f870

- Add index-only scan support to btree_gist. inet, cidr, and timetz
indexes still cannot support index-only scans, because they don't
store the original unmodified value in the index, but a derived
approximate value.
http://git.postgresql.org/pg/commitdiff/e09b48316c22fce727bce3c89fa64fc627787e6a

- Add index-only scan support to inet GiST opclass. Andreas Karlsson
http://git.postgresql.org/pg/commitdiff/3a20b0e7b6dae48cd6be1257e9017663f1402b91

Álvaro Herrera pushed:

- vacuumdb: Check result status of PQsendQuery. Noticed by Coverity
http://git.postgresql.org/pg/commitdiff/871293fb7fa869fbe0f202bef2e0d781bfd21b3e

- Fix gram.y comment to match reality. There are other comments in
there that don't precisely match what's implemented, but this one
confused me enough to be worth fixing.
http://git.postgresql.org/pg/commitdiff/dc8e05295ab126bc4c943cab3e8e117489ecb246

- Fix bug for array-formatted identities of user mappings. I failed
to realize that server names reported in the object args array would
get quoted, which is wrong; remove that, making sure that it's only
quoted in the string-formatted identity. This bug was introduced by
my commit cf34e373, which was backpatched, but since object
name/args arrays are new in commit a676201490c8, there is no need to
backpatch this any further.
http://git.postgresql.org/pg/commitdiff/b3196e65f5bfc997ec7fa3f91645a09289c10dee

- Add OID output argument to DefineTSConfiguration ... which is set to
the OID of a copied text search config, whenever the COPY clause is
used. This is in the spirit of commit a2e35b53c39.
http://git.postgresql.org/pg/commitdiff/8217fb1441ce4b4e1785f9acfa0ce50039247a10

- Return ObjectAddress in many ALTER TABLE sub-routines. Since commit
a2e35b53c39b2a, most CREATE and ALTER commands return the
ObjectAddress of the affected object. This is useful for event
triggers to try to figure out exactly what happened. This patch
extends this idea a bit further to cover ALTER TABLE as well: an
auxiliary ObjectAddress is returned for each of several subcommands
of ALTER TABLE. This makes it possible to decode with precision
what happened during execution of any ALTER TABLE command; for
instance, which constraint was added by ALTER TABLE ADD CONSTRAINT,
or which parent got dropped from the parents list by ALTER TABLE NO
INHERIT. As with the previous patch, there is no immediate
user-visible change here. This is all really just continuing what
c504513f83a9ee8 started. Reviewed by Stephen Frost.
http://git.postgresql.org/pg/commitdiff/bdc3d7fa2376a7a1e977383cc3221cfe44c4a893

Tom Lane pushed:

- Apply table and domain CHECK constraints in name order. Previously,
CHECK constraints of the same scope were checked in whatever order
they happened to be read from pg_constraint. (Usually, but not
reliably, this would be creation order for domain constraints and
reverse creation order for table constraints, because of differing
implementation details.) Nondeterministic results of this sort are
problematic at least for testing purposes, and in discussion it was
agreed to be a violation of the principle of least astonishment.
Therefore, borrow the principle already established for triggers,
and apply such checks in name order (using strcmp() sort rules).
This lets users control the check order if they have a mind to.
Domain CHECK constraints still follow the rule of checking lower
nested domains' constraints first; the name sort only applies to
multiple constraints attached to the same domain. In passing, I
failed to resist the temptation to wordsmith a bit in
create_domain.sgml. Apply to HEAD only, since this could result in
a behavioral change in existing applications, and the potential
regression test failures have not actually been observed in our
buildfarm.
http://git.postgresql.org/pg/commitdiff/e5f455f59fed0632371cddacddd79895b148dc07

- Fix ExecOpenScanRelation to take a lock on a ROW_MARK_COPY relation.
ExecOpenScanRelation assumed that any relation listed in the
ExecRowMark list has been locked by InitPlan; but this is not true
if the rel's markType is ROW_MARK_COPY, which is possible if it's a
foreign table. In most (possibly all) cases, failure to acquire a
lock here isn't really problematic because the parser, planner, or
plancache would have taken the appropriate lock already. In
principle though it might leave us vulnerable to working with a
relation that we hold no lock on, and in any case if the executor
isn't depending on previously-taken locks otherwise then it should
not do so for ROW_MARK_COPY relations. Noted by Etsuro Fujita.
Back-patch to all active versions, since the inconsistency has been
there a long time. (It's almost certainly irrelevant in 9.0, since
that predates foreign tables, but the code's still wrong on its own
terms.)
http://git.postgresql.org/pg/commitdiff/feeb526cfe33657b8aa8b0cdd45b2ef0d9898877

- Upgrade src/port/rint.c to be POSIX-compliant. The POSIX spec says
that rint() rounds halfway cases to nearest even. Our substitute
implementation failed to do that, rather rounding halfway cases away
from zero; and it also got some other cases (such as minus zero)
wrong. This led to observable cross-platform differences, as
reported in bug #12885 from Rich Schaaf; in particular, casting from
float to int didn't honor round-to-nearest-even on builds using
rint.c. Implement something that attempts to cover all cases per
spec, and add some simple regression tests so that we'll notice if
any platforms still get this wrong. Although this is a bug fix, no
back-patch, as a behavioral change in the back branches was agreed
not to be a good idea. Pedro Gimeno Fortea, reviewed by Michael
Paquier and myself
http://git.postgresql.org/pg/commitdiff/06bf0dd6e354c765403d1331cc9896b360754521

- Add an ASSERT statement in plpgsql. This is meant to make it easier
to insert simple debugging cross-checks in plpgsql functions. Pavel
Stehule, reviewed by Jim Nasby
http://git.postgresql.org/pg/commitdiff/a4847fc3ef139ba9a8ffebb6ffa06ee72078ffa2

- Suppress some unused-variable complaints in new LOCK_DEBUG code.
Jeff Janes
http://git.postgresql.org/pg/commitdiff/bed756a820a2c1ee359f5f5b44806e3599190e95

- Tweak __attribute__-wrapping macros for better pgindent results.
This improves on commit bbfd7edae5aa5ad5553d3c7e102f2e450d4380d4 by
making two simple changes: * pg_attribute_noreturn now takes
parentheses, ie pg_attribute_noreturn(). Likewise
pg_attribute_unused(), pg_attribute_packed(). This reduces
pgindent's tendency to misformat declarations involving them. *
attributes are now always attached to function declarations, not
definitions. Previously some places were taking creative shortcuts,
which were not merely candidates for bad misformatting by pgindent
but often were outright wrong anyway. (It does little good to put a
noreturn annotation where callers can't see it.) In any case, if we
would like to believe that these macros can be used with non-gcc
compilers, we should avoid gratuitous variance in usage patterns. I
also went through and manually improved the formatting of a lot of
declarations, and got rid of excessively repetitive (and now
obsolete anyway) comments informing the reader what
pg_attribute_printf is for.
http://git.postgresql.org/pg/commitdiff/785941cdc359c6e595201ffb0df9d28f3f7173a4

- Better fix for misuse of Float8GetDatumFast(). We can use that
macro as long as we put the value into a local variable. Commit
735cd6128 was not wrong on its own terms, but I think this way looks
nicer, and it should save a few cycles on 32-bit machines.
http://git.postgresql.org/pg/commitdiff/2c33e0fbceb01d0ecd78330feef1315682c64bc4

- Minor code cleanups in pgbench expression support. Get rid of
unnecessary expr_yylex declaration (we haven't supported flex 2.5.4
in a long time, and even if we still did, the declaration in
pgbench.h makes this one unnecessary and inappropriate). Fix
copyright dates, improve some layout choices, etc.
http://git.postgresql.org/pg/commitdiff/e9dd03c03aeed6486129e3101695b13d469c2985

- Remove a couple other vestigial yylex() declarations. These were
workarounds for a long-gone flex bug; all supported versions of flex
emit an extern declaration as expected.
http://git.postgresql.org/pg/commitdiff/9a8e23311cac14168df6644e03d533a4b07f933e

- Make ginbuild's funcCtx be independent of its tmpCtx. Previously
the funcCtx was a child of the tmpCtx, but that was broken by commit
eaa5808e8ec4e82ce1a87103a6b6f687666e4e4c, which made
MemoryContextReset() delete, not reset, child contexts. The
behavior of having a tmpCtx reset also clear the other context seems
rather dubious anyway, so let's just disentangle them. Per report
from Erik Rijkers. In passing, fix badly-inaccurate comments about
these contexts.
http://git.postgresql.org/pg/commitdiff/1601830ec20d56dc7bf6b60a34f69841429e4825

- Add vacuum_delay_point call in compute_index_stats's per-sample-row
loop. Slow functions in index expressions might cause this loop to
take long enough to make it worth being cancellable. Probably it
would be enough to call CHECK_FOR_INTERRUPTS here, but for
consistency with other per-sample-row loops in this file, let's use
vacuum_delay_point. Report and patch by Jeff Janes. Back-patch to
all supported branches.
http://git.postgresql.org/pg/commitdiff/e4cbfd673d530a3e841db26a74f22e11a991205a

Bruce Momjian pushed:

- Add support for ALTER TABLE IF EXISTS ... RENAME CONSTRAINT. Also
add regression test. Previously this was documented to work, but
didn't.
http://git.postgresql.org/pg/commitdiff/1d8198bb44e7e7e3e96d96942f642e9964111628

- doc: update NUMERIC to state that only some ops are exact. Report
by Tom Lane
http://git.postgresql.org/pg/commitdiff/278edd9ed36c7722cbae27e0e96a08964da69eb5

- docs: clarify when MVCC snapshot is taken. Report by Álvaro
Hernández Tortosa
http://git.postgresql.org/pg/commitdiff/66c8040d509c86fd2f215c06eb16d82e570d3fb6

- psql: show proper row count in \x mode for zero-column output.
Also, fix pager enable selection for such cases, and other cleanups
for zero-column output. Report by Thom Brown
http://git.postgresql.org/pg/commitdiff/376a0c4547fe98c45476647596ce9c9b394f8415

- PL/pgSQL docs: recommend format() for query construction.
Previously only concatenation was recommended. Report by Pavel
Stehule
http://git.postgresql.org/pg/commitdiff/0e1f6d8132b4da3e0727bb4918b9ea51446a9c41

- btree_gin: properly call DirectFunctionCall1() Previously we called
DirectFunctionCall3() with dummy arguments. Patch by Jon Nelson
http://git.postgresql.org/pg/commitdiff/843cd0bfe6246d94d9b34a7f36bbb76fdba87b74

- Revert commit 843cd0bfe6246d94d9b34a7f36bbb76fdba87b74. Report by
Tom Lane
http://git.postgresql.org/pg/commitdiff/11226e3817687fcb70fb49d75fdf592e7f3884f6

Kevin Grittner pushed:

- Reduce pinning and buffer content locking for btree scans. Even
though the main benefit of the Lehman and Yao algorithm for btrees
is that no locks need be held between page reads in an index search,
we were holding a buffer pin on each leaf page after it was read
until we were ready to read the next one. The reason was so that we
could treat this as a weak lock to create an "interlock" with
vacuum's deletion of heap line pointers, even though our README file
pointed out that this was not necessary for a scan using an MVCC
snapshot. The main goal of this patch is to reduce the blocking of
vacuum processes by in-progress btree index scans (including a
cursor which is idle), but the code rearrangement also allows for
one less buffer content lock to be taken when a forward scan steps
from one page to the next, which results in a small but consistent
performance improvement in many workloads. This patch leaves
behavior unchanged for some cases, which can be addressed separately
so that each case can be evaluated on its own merits. These
unchanged cases are when a scan uses a non-MVCC snapshot, an
index-only scan, and a scan of a btree index for which modifications
are not WAL-logged. If later patches allow all of these cases to
drop the buffer pin after reading a leaf page, then the btree vacuum
process can be simplified; it will no longer need the
"super-exclusive" lock to delete tuples from a page. Reviewed by
Heikki Linnakangas and Kyotaro Horiguchi
http://git.postgresql.org/pg/commitdiff/2ed5b87f96d473962ec5230fd820abfeaccb2069

Tatsuo Ishii pushed:

- Make SyncRepWakeQueue to a static function. It is only used in
src/backend/replication/syncrep.c. Back-patch to all supported
branches except 9.1 which declares the function as static.
http://git.postgresql.org/pg/commitdiff/656ea810e5e1111bc4d741275b37310a32ff890c

Andrew Dunstan pushed:

- Fix portability issues with stddev in pg_stat_statements. Stddev is
calculated on the fly, and the code in commit 717f70953264 was using
Float8GetDatumFast() inappropriately to convert the result to a
Datum. Mea culpa. It now uses Float8GetDatum().
http://git.postgresql.org/pg/commitdiff/735cd6128a6a401671126443a9af4324932a38d6

- Add stats for min, max, mean, stddev times to pg_stat_statements.
The new fields are min_time, max_time, mean_time and stddev_time.
Based on an original patch from Mitsumasa KONDO, modified by me.
Reviewed by Petr Jelínek.
http://git.postgresql.org/pg/commitdiff/717f709532642f5f7756785c9be17b7ffcec8ae8

- Use standard librart sqrt function in pg_stat_statements. The
stddev calculation included a faster but unportable sqrt function.
This is not worth the extra effort, and won't work everywhere. If
the standard library function is good enough for the SQL function it
should be good enough here too.
http://git.postgresql.org/pg/commitdiff/cfe12763c32437bc708a64ce88a90c7544f16185

- Add a pager_min_lines setting to psql. If set, the pager will not
be used unless this many lines are to be displayed, even if that is
more than the screen depth. Default is zero, meaning it's disabled.
There is probably more work to be done in giving the user control
over when the pager is used, particularly when wide output forces
use of the pager regardless of how many lines there are, but this is
a start.
http://git.postgresql.org/pg/commitdiff/7655f4ccea570d57c4d473cd66b755c03c904942

Peter Eisentraut pushed:

- Fix whitespace
http://git.postgresql.org/pg/commitdiff/16bbb96a2b48d0f525b7fb2f6a001b16719467a9

== Rejected Patches (for now) ==

No one was disappointed this week :-)

== Pending Patches ==

Pavel Stehule sent in two more revisions of a patch to add a --strict
option to pg_dump for missing tables.

Bruce Momjian sent in three more revisions of a patch to add the asciidoc
output format to psql.

David Steele sent in two more revisions of a patch to to add a
pg_audit extension.

Peter Geoghegan and Andrew (RhodiumToad) Gierth sent in two more
revisions of a patch to add abbreviated keys for NUMERIC.

Michael Paquier sent in two revisions of a patch to expose
PG_VERSION_NUM to developers.

Michael Paquier sent in another revision of a patch to add a
table-level log_autovacuum_min_duration.

Kyotaro HORIGUCHI sent in a patch to remove individual phases to mark
unique joins.

Andres Freund sent in another revision of a patch to add replication
identifiers.

Amit Kapila sent in a patch to fix a bug in dsm_attach().

Peter Geoghegan sent in a patch to add DatumGetUInt32() around the
hash_any() and hash_uint32() calls within varlena.c.

Heikki Linnakangas sent in another revision of a patch to use Intel
SSE4.2 CRC instructions where available.

Álvaro Herrera sent in another revision of a patch to implement
parsing utility commands.

Kaigai Kouhei sent in another revision of a patch to add a custom JOIN
API.

Fabrízio de Royes Mello sent in a patch to fix a bug with indexes on
unlogged tables.

Amit Kapila sent in two more revisions of a patch to implement
parallel sequential scan.

Antonin Houska sent in two revisions of a WIP patch to enable spliting
hash index buckets.

Peter Geoghegan sent in another revision of a patch to implement
INSERT ... ON CONFLICT IGNORE (and UPDATE).

Haribabu Kommi sent in another revision of a patch to add a catalog
view to pg_hba.conf.

David Rowley sent in another revision of a patch to improve
performance for outer joins where the outer side is unique.

Tom Lane sent in another revision of a patch to manipulate complex
types as non-contiguous structures in-memory.

Fabien COELHO sent in another revision of a patch to improve pgbench
syntax error messages.

Fabien COELHO sent in another revision of a patch to extend pgbench
expressions with functions.

Pavel Stehule sent in another revision of a patch to add a
row_to_array function.

Michael Paquier sent in a patch to describe precise rounding behavior
of numeric and double precision in the docs.

Andres Freund sent in a patch to make heap extension scale better.