== PostgreSQL Weekly News - May 01 2016 ==
David Fetter <david <at> fetter.org>
2016-05-02 05:48:08 GMT
== PostgreSQL Weekly News - May 01 2016 ==
== PostgreSQL Product News ==
BigSQL integrated PostgreSQL distribution from SCG released.
jpgAgent is a job scheduler for PostgreSQL written in Java.
Ora2PG 18.4 a migration system for moving from Oracle and MySQL to
pgBadger 8.1, a parallel PostgreSQL log analyzer written in Perl, released:
pgCluu 2.5, a Perl program to audit PostgreSQL performance, released.
pgpool-II 3.5.2, 3.4.6, 3.3.10, 3.2.15, 3.1.18, and pgpoolAdmin 3.5.2
released. pgpool-II is a connection pooler and replication system for
== PostgreSQL Jobs for May ==
== PostgreSQL Local ==
FOSS4G NA, will be held May 2-5, 2016 in Raleigh, North Carolina.
PGCon 2016 will be held May 17-21, 2016 in Ottawa.
This year's Swiss PGDay will be held on June 24, 2016 at the
University of Applied Sciences in Rapperswil (Switzerland).
"5432 ... Meet us!", will take place in Milan, Italy on June 28-29, 2016.
Registration is open.
PG Day UK 2016 will be 5th July 2016.
PostgresOpen 2016 in will be held in Dallas, Texas September 13-16.
The CfP is open.
PostgreSQL Session will be held on September 22th, 2016, in Lyon,
France. The submission deadline is May 20, 2016. Send proposals to
call-for-paper AT postgresql-sessions DOT org.
PgConf Silicon Valley 2016 will be held on November 14-16, 2016.
== 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.org, German language
to pwn <at> pgug.de, Italian language to pwn <at> itpug.org. Spanish language
to pwn <at> arpug.com.ar.
== Applied Patches ==
Peter Eisentraut pushed:
- doc: Fix typo From: Andreas Seltenreich
<andreas.seltenreich <at> credativ.de>
- Update GETTEXT_FILES after config and controldata refactoring.
- pg_dump: Message style improvements.
- pg_dump: Message style improvements forgotten in
- doc: Minor wording changes. From: Dmitry Igrishin <dmitigr <at> gmail.com>
Tom Lane pushed:
- Try harder to detect a port conflict in PostgresNode.pm. Commit
fab84c7787f25756 tried to get away without doing an actual bind(),
but buildfarm results show that that doesn't get the job done. So
we must really bind to the target port --- and at least on my Linux
box, we need a listen() as well, or conflicts won't be detected. We
rely on SO_REUSEADDR to prevent problems from starting a postmaster
on the socket immediately after we've bound to it in the test code.
(There may be platforms where that doesn't work too well. But
fortunately, we only really care whether this works on Windows, and
there the default behavior should be OK.)
- New method for preventing compile-time calculation of degree
constants. Commit 65abaab547a5758b tried to prevent the scaling
constants used in the degree-based trig functions from being
precomputed at compile time, because some compilers do that with
functions that don't yield results identical-to-the-last-bit to what
you get at runtime. A report from Peter Eisentraut suggests that
some recent compilers are smart enough to see through that trick,
though. Instead, let's put the inputs to these calculations into
non-const global variables, which should be a more reliable way of
convincing the compiler that it can't assume that they are
compile-time constants. (If we really get desperate, we could mark
these variables "volatile", but I do not believe we should have to.)
- Yet more portability hacking for degree-based trig functions. The
true explanation for Peter Eisentraut's report of inexact asind
results seems to be that (a) he's compiling into x87 instruction
set, which uses wider-than-double float registers, plus (b) the
library function asin() on his platform returns a result that is
wider than double and is not rounded to double width. To fix, we
have to force the function's result to be rounded comparably to what
happened to the scaling constant asin_0_5. Experimentation suggests
that storing it into a volatile local variable is the least ugly way
of making that happen. Although only asin() is known to exhibit an
observable inexact result, we'd better do this in all the places
where we're hoping to get an exact result by scaling.
- Fix order of shutdown cleanup operations in PostgresNode.pm.
Previously, database clusters created by a TAP test were shut down
by DESTROY methods attached to the PostgresNode objects representing
them. The trouble with that is that if the objects survive into the
final global destruction phase (which they do), Perl executes the
DESTROY methods in an unspecified order. Thus, the order of
shutdown of multiple clusters was indeterminate, which might lead to
not-very-reproducible errors getting logged (eg from a slave whose
master might or might not get killed first). Worse, the File::Temp
objects representing the temporary PGDATA directories might get
destroyed before the PostgresNode objects, resulting in attempts to
delete PGDATA directories that still have live servers in them. On
Windows, this would lead to directory deletion failures; on Unix, it
usually had no effects worse than erratic "could not open temporary
statistics file "pg_stat/global.tmp": No such file or directory" log
messages. While none of this would affect the reported result of
the TAP test, which is already determined, it could be very
confusing when one is trying to understand from the logs what went
wrong with a failed test. To fix, do the postmaster shutdowns in an
END block rather than at object destruction time. The END block
will execute at a well-defined (and reasonable) time during script
termination, and it will stop the postmasters in order of
PostgresNode object creation. (Perhaps we should change that to be
reverse order of creation, but the main point here is that we now
have control which we did not before.) Use "pg_ctl stop", not an
asynchronous kill(SIGQUIT), so that we wait for the postmasters to
shut down before proceeding with directory deletion. Deletion of
temporary directories still happens in an unspecified order during
global destruction, but I can see no reason to care about that once
the postmasters are stopped.
- Add a --brief option to git_changelog. In commit c0b050192, Andres
introduced the idea of including one-line commit references in our
major release notes. Teach git_changelog to emit a (lightly
adapted) version of that format, so that we don't have to
laboriously add it to the notes after the fact. The default output
isn't changed, since I anticipate still using that for minor release
- Clean up parsing of synchronous_standby_names GUC variable. Commit
989be0810dffd08b added a flex/bison lexer/parser to interpret
synchronous_standby_names. It was done in a pretty crufty way,
though, making assorted end-use sites responsible for calling the
parser at the right times. That was not only vulnerable to errors
of omission, but made it possible that lexer/parser errors occur at
very undesirable times, and created memory leakages even if there
was no error. Instead, perform the parsing once during
check_synchronous_standby_names and let guc.c manage the resulting
data. To do that, we have to flatten the parsed representation into
a single hunk of malloc'd memory, but that is not very hard. While
at it, work a little harder on making useful error reports for
parsing problems; the previous code felt that
"synchronous_standby_names parser returned 1" was an appropriate
user-facing error message. (To be fair, it did also log a syntax
error message, but separately from the GUC problem report, which is
at best confusing.) It had some outright bugs in the face of
invalid input, too. I (tgl) also concluded that we need to restrict
unquoted names in synchronous_standby_names to be just SQL
identifiers. The previous coding would accept darn near anything,
which (1) makes the quoting convention both nearly-unnecessary and
formally ambiguous, (2) makes it very hard to understand what is a
syntax error and what is a creative interpretation of the input as a
standby name, and (3) makes it impossible to further extend the
syntax in future without a compatibility break. I presume that
we're intending future extensions of the syntax, else this parsing
infrastructure is massive overkill, so (3) is an important
objection. Since we've taken a compatibility hit for non-identifier
names with this change anyway, we might as well lock things down now
and insist that users use double quotes for standby names that
aren't identifiers. Kyotaro Horiguchi and Tom Lane
- Use memmove() not memcpy() to slide some pointers down. The
previous coding here was formally undefined, though it seems to
accidentally work on most platforms in the buildfarm. Caught by
some OpenBSD platforms in which libc contains an assertion check for
overlapping areas passed to memcpy(). Thomas Munro
- Revert "Convert contrib/seg's bool-returning SQL functions to V1
call convention." This reverts commit
c8e81afc60093b199a128ccdfbb692ced8e0c9cd. That turns out to have
been based on a faulty diagnosis of why the VS2015 build was
misbehaving. Instead, we need to fix DatumGetBool().
- Adjust DatumGetBool macro, this time for sure. Commit 23a41573c
attempted to fix the DatumGetBool macro to ignore bits in a Datum
that are to the left of the actual bool value. But it did that by
casting the Datum to bool; and on compilers that use C99 semantics
for bool, that ends up being a whole-word test, not a 1-byte test.
This seems to be the true explanation for contrib/seg failing in
VS2015. To fix, use GET_1_BYTE() explicitly. I think in the
previous patch, I'd had some idea of not having to commit to bool
being exactly 1 byte wide, but regardless of what the compiler's
bool is, boolean columns and Datums are certainly 1 byte wide. The
previous fix was (eventually) back-patched into all active versions,
so do likewise with this one.
- Fix mishandling of equivalence-class tests in parameterized plans.
Given a three-or-more-way equivalence class, such as X.Y = Y.Y =
Z.Z, it was possible for the planner to omit one of the quals needed
to enforce that all members of the equivalence class are actually
equal. This only happened in the case of a parameterized join node
for two of the relations, that is a plan tree like Nested Loop ->
Scan X -> Nested Loop -> Scan Y -> Scan Z Filter: Z.Z = X.X The
eclass machinery normally expects to apply X.X = Y.Y when those two
relations are joined, but in this shape of plan tree they aren't
joined until the top node --- and, if the lower nested loop is
marked as parameterized by X, the top node will assume that the
relevant eclass condition(s) got pushed down into the lower node.
On the other hand, the scan of Z assumes that it's only responsible
for constraining Z.Z to match any one of the other eclass members.
So one or another of the required quals sometimes fell between the
cracks, depending on whether consideration of the eclass in
get_joinrel_parampathinfo() for the lower nested loop chanced to
generate X.X = Y.Y or X.X = Z.Z as the appropriate constraint there.
If it generated the latter, it'd erroneously suppose that the Z scan
would take care of matters. To fix, force X.X = Y.Y to be generated
and applied at that join node when this case occurs. This is
*extremely* hard to hit in practice, because various planner
behaviors conspire to mask the problem; starting with the fact that
the planner doesn't really like to generate a parameterized plan of
the above shape. (It might have been impossible to hit it before we
tweaked things to allow this plan shape for star-schema cases.)
Many thanks to Alexander Kirkouski for submitting a reproducible
test case. The bug can be demonstrated in all branches back to 9.2
where parameterized paths were introduced, so back-patch that far.
- Remove warning about num_sync being too large in
synchronous_standby_names. If we're not going to reject such setups
entirely, throwing a WARNING in check_synchronous_standby_names() is
unhelpful, because it will cause the warning to be logged again
every time the postmaster receives SIGHUP. Per discussion, just
remove the warning. In passing, improve the documentation for
synchronous_commit, which had not gotten the word that now there can
be more than one synchronous standby.
- Fix planner crash from pfree'ing a partial path that a GatherPath
uses. We mustn't run generate_gather_paths() during
add_paths_to_joinrel(), because that function can be invoked
multiple times for the same target joinrel. Not only is it wasteful
to build GatherPaths repeatedly, but a later add_partial_path()
could delete the partial path that a previously created GatherPath
depends on. Instead establish the convention that we do
generate_gather_paths() for a rel only just before set_cheapest().
The code was accidentally not broken for baserels, because as of
today there never is more than one partial path for a baserel. But
that assumption obviously has a pretty short half-life, so move the
generate_gather_paths() calls for those cases as well. Also add
some generic comments explaining how and why this all works. Per
fuzz testing by Andreas Seltenreich. Report:
<871t5pgwdt.fsf <at> credativ.de>
- Small improvements to OPTIMIZER_DEBUG code. Now that Paths have
their own rows field, print that rather than the parent relation's
rowcount. Show the relid sets associated with Paths using table
names rather than numbers; since this code is able to print simple
Var references using table names, it seems a bit silly that
print_relids can't. Print the cheapest_parameterized_paths list for
a RelOptInfo, and include information about a parameterized path's
required_outer rels. Noted while trying to use this feature to
debug Alexander Kirkouski's recent bug report.
- Update contrib/unaccent documentation about its unaccent.rules file.
Commit 1bbd52cb9a4aa61a didn't bother with such niceties.
- Add a --non-master-only option to git_changelog. This has the
inverse effect of --master-only. It's needed to help find cases
where a commit should not be described in major release notes
because it was back-patched into older branches, though not at the
same time as the HEAD commit.
Kevin Grittner pushed:
- Fix C comment typo and redundant test
- Add a few entries to the tail of time mapping, to see old values.
Without a few entries beyond old_snapshot_threshold, the lookup
would often fail, resulting in the more aggressive pruning or vacuum
being skipped often enough to matter. This was very clearly shown
by a python test script posted by Ants Aasma, and was likely a
factor in an earlier but somewhat less clear-cut test case posted by
Jeff Janes. This patch makes no change to the logic, per se -- it
just makes the array of mapping entries big enough to make lookup
misses based on timing much less likely. An occasional miss is
still possible if a thread stalls for more than 10 minutes, but that
does not create any problem with correctness of behavior. Besides,
if things are so busy that a thread is stalling for more than 10
minutes, it is probably OK to skip the more aggressive cleanup at
that particular point in time.
Magnus Hagander pushed:
- Fix typo in comment. Author: Daniel Gustafsson
- Fix typo. Author: Thomas Munro
Robert Haas pushed:
- Enable parallel query by default. Change max_parallel_degree
default from 0 to 2. It is possible that this is not a good idea,
or that we should go with 1 worker rather than 2, but we won't find
out without trying it. Along the way, reword the documentation for
max_parallel_degree a little bit to hopefully make it more clear.
Discussion: 20160420174631.3qjjhpwsvvx5bau5 <at> alap3.anarazel.de
- Fix pg_get_functiondef to dump parallel-safety markings. Ashutosh
- Fix EXPLAIN VERBOSE output for parallel aggregate. The way that
PartialAggregate and FinalizeAggregate plan nodes were displaying
output columns before was bogus. Now, FinalizeAggregate produces
the same outputs as an Aggregate would have produced, while
PartialAggregate produces each of those outputs prefixed by the word
PARTIAL. Discussion: 12585.1460737650 <at> sss.pgh.pa.us Patch by me,
reviewed by David Rowley.
- Remove mergeHyperLogLog. It's buggy. If somebody needs this later,
they'll need to put back a non-buggy vesion of it. Discussion:
CAM3SWZT-i6R9JU5YXa8MJUou2_r3LfGJZpQ9tYa1BYxfkj0=cQ <at> mail.gmail.com
CAM3SWZRUOLsYoTT83QgdUy9D8ehYWm_nvbrrfcOOzikiRfFY7g <at> mail.gmail.com
- Clean up a few parallelism-related things that pgindent wants to
mangle. In nodeFuncs.c, pgindent wants to introduce spurious
indentation into the definitions of planstate_tree_walker and
planstate_walk_subplans. Fix that by spreading the definition out
across several lines, similar to what is already done for other
walker functions in that file. In execParallel.c, in the definition
of SharedExecutorInstrumentation, pgindent wants to insert more
whitespace between the type name and the member name. That causes
it to mangle comments later on the line. Fix by moving the comments
out of line. Now that we have a bit more room, add some more
details that may be useful to the next person reading this code.
- Update typedefs.list file in preparation for pgindent run In
addition to adding new typedefs, I also re-sorted the file so that
various entries add piecemeal, mostly or entirely by me, were
alphabetized the same way as other entries in the file.
- Remove inadvertently commited vim swapfile. If you were wondering
what editor I use, now you know.
- Tighten up sanity checks for parallel aggregate in execQual.c.
- Change postgresql.conf.sample to say that fsync=off will corrupt
data. Discussion: 24748.1461764666 <at> sss.pgh.pa.us Per a suggestion
from Craig Ringer. This wording from Tom Lane, following
- Fix wrong word. Commit a31212b429cd3397fb3147b1a584ae33224454a6 was
a little too hasty. Per report from Tom Lane.
Teodor Sigaev pushed:
- Fix tsearch docs. Remove mention of setweight(tsquery) which wasn't
included in 9.6. Also replace old forgotten phrase operator to new
one. Dmitry Ivanov
- Prevent multiple cleanup process for pending list in GIN.
Previously, ginInsertCleanup could exit early if it detects that
someone else is cleaning up the pending list, without waiting for
that someone else to finish the job. But in this case vacuum could
miss tuples to be deleted. Cleanup process now locks metapage with
a help of heavyweight LockPage(ExclusiveLock), and it guarantees
that there is no another cleanup process at the same time. Lock is
taken differently depending on caller of cleanup process: any
vacuums and gin_clean_pending_list() will be blocked until lock
becomes available, ordinary insert uses conditional lock to prevent
indefinite waiting on lock. Insert into pending list doesn't use
this lock, so insertion isn't blocked. Also, patch adds stopping of
cleanup process when at-start-cleanup-tail is reached in order to
prevent infinite cleanup in case of massive insertion. But it will
stop only for automatic maintenance tasks like autovacuum. Patch
introduces choice of limit of memory to use: autovacuum_work_mem,
maintenance_work_mem or work_mem depending on call path. Patch for
previous releases should be reworked due to changes between 9.6 and
previous ones in this area. Discover and diagnostics by Jeff Janes
and Tomas Vondra Patch by me with some ideas of Jeff Janes
- Prevent to use magic constants. Use macroses for definition
amstrategies/amsupport fields instead of hardcoded values. Author:
Nikolay Shaplov with addition for contrib/bloom
Noah Misch pushed:
- Impose a full barrier in generic-xlc.h atomics functions.
pg_atomic_compare_exchange_*_impl() were providing only the
semantics of an acquire barrier. Buildfarm members hornet and
mandrill revealed this deficit beginning with commit
008608b9d51061b1f598c197477b3dc7be9c4a64. While we have no report
of symptoms in 9.5, we can't rule out the possibility of certain
compilers, hardware, or extension code relying on these functions'
specified barrier semantics. Back-patch to 9.5, where commit
b64d92f1a5602c55ee8b27a7ac474f03b7aee340 introduced atomics.
Reviewed by Andres Freund.
Andres Freund pushed:
- Don't open formally non-existent segments in _mdfd_getseg(). Before
this commit _mdfd_getseg(), in contrast to mdnblocks(), did not
verify whether all segments leading up to the to-be-opened one, were
RELSEG_SIZE sized. That is e.g. not the case after truncating a
relation, because later segments just get truncated to zero length,
not removed. Once a "non-existent" segment has been opened in a
session, mdnblocks() will return wrong results, causing errors like
"could not read block %u in file" when accessing blocks. Closing the
session, or the later arrival of relevant invalidation messages,
would "fix" the problem. That, so far, was mostly harmless, because
most segment accesses are only done after an mdnblocks() call. But
since 428b1d6b29ca we try to open segments that might have been
deleted, to trigger kernel writeback from a backend's queue of
recent writes. To fix check segment sizes in _mdfd_getseg() when
opening previously unopened segments. In practice this shouldn't
imply a lot of additional lseek() calls, because mdnblocks() will
most of the time already have opened all relevant segments. This
commit also fixes a second problem, namely that _mdfd_getseg(
EXTENSION_RETURN_NULL) extends files during recovery, which is not
desirable for the mdwriteback() case. Add
EXTENSION_REALLY_RETURN_NULL, which does not behave that way, and
use it. Reported-By: Thom Brown Author: Andres Freund, Abhijit
Menon-Sen Reviewd-By: Robert Haas, Fabien Coehlo Discussion:
CAA-aLv6Dp_ZsV-44QA-2zgkqWKQq=GedBX2dRSrWpxqovXK=Pg <at> mail.gmail.com
- Emit invalidations to standby for transactions without xid. So far,
when a transaction with pending invalidations, but without an
assigned xid, committed, we simply ignored those invalidation
messages. That's problematic, because those are actually sent for a
reason. Known symptoms of this include that existing sessions on a
hot-standby replica sometimes fail to notice new concurrently built
indexes and visibility map updates. The solution is to WAL log such
invalidations in transactions without an xid. We considered to
alternatively force-assign an xid, but that'd be problematic for
vacuum, which might be run in systems with few xids. Important:
This adds a new WAL record, but as the patch has to be back-patched,
we can't bump the WAL page magic. This means that standbys have to
be updated before primaries; otherwise "PANIC: standby_redo: unknown
op code 32" errors can be encountered. XXX: Reported-By: Васильев
Дмитрий, Masahiko Sawada Discussion:
CAB-SwXY6oH=9twBkXJtgR4UC1NqT-vpYAtxCseME62ADwyK5OA <at> mail.gmail.com
CAD21AoDpZ6Xjg=gFrGPnSn4oTRRcwK1EBrWCq9OqOHuAcMMC=w <at> mail.gmail.com
- Remember asking for feedback during walsender shutdown. Since
5a991ef8 we're explicitly asking for feedback from the receiving
side when shutting down walsender, if there's not yet replicated
data. Unfortunately we didn't remember (i.e. set
waiting_for_ping_response to true) having asked for feedback,
leading to scenarios in which replies were requested at a high
frequency. I can't reproduce this problem on my laptop, I think
that's because the problem requires a significant TCP window to
manifest due to the !pq_is_send_pending() condition. But since this
clearly is a bug, let's fix it. There's quite possibly more wrong
than just this though. While fiddling with WalSndDone(), I rewrote
a hard to understand comment about looking at the flush vs. the
write position. Reported-By: Nick Cleaton, Magnus Hagander Author:
Nick Cleaton Discussion:
CAFgz3kus=rC_avEgBV=+hRK5HYJ8vXskJRh8yEAbahJGTzF2VQ <at> mail.gmail.com
CABUevExsjROqDcD0A2rnJ6HK6FuKGyewJr3PL12pw85BHFGS2Q <at> mail.gmail.com
Backpatch: 9.4, were 5a991ef8 introduced the use of feedback
messages during shutdown.
Andrew Dunstan pushed:
- Support building with Visual Studio 2015. Adjust the way we detect
the locale. As a result the minumum Windows version supported by
VS2015 and later is Windows Vista. Add some tweaks to remove new
compiler warnings. Remove documentation references to the now
obsolete msysGit. Michael Paquier, somewhat edited by me, reviewed
by Christian Ullrich. Backpatch to 9.5
- Fix typo in VS2015 patch. reported by Christian Ullrich
- Fix comment whitespace in VS2105 patch. per gripe from Michael
== Rejected Patches (for now) ==
No one was disappointed this week
== Pending Patches ==
Stephen Frost sent in another revision of a patch to fix pg_dump for
Sehrope Sarkuni sent in a patch to add jsonb_compact(...) for
whitespace-free jsonb to text.
Peter Eisentraut sent in another revision of a patch to fix an OpenSSL
error queue bug.
Kyotaro HORIGUCHI sent in two more revisions of a patch to fix
synchronous replication update configuration.
Ashutosh Sharma sent in a patch to allow pg_basebackup to create
pg_stat_tmp and pg_replslot as an empty directories if they are
Etsuro Fujita sent in a patch to fix subtransaction callbacks in the
Christian Ullrich sent in three revisions of a patch to enable
parallel builds with MSVC.
Dean Rasheed sent in a patch to fix an issue in psql's \ev feature
which adds support for missing VIEW options like WITH CHECK OPTION.
Daniel Gustafsson sent in a patch to remove some unused macros from
Julien Rouhaud sent in two revisions of a patch to fix an issue with
FK joins that could cause a segfault.
Craig Ringer sent in a patch to allow a stop LSN to be specified to
Andreas Karlsson sent in a patch to fix the parallel safety markings
for some built-in functions that got missed in the shuffle.
Ian Lawrence Barwick sent in a patch to add tab completion to psql's
Amit Kapila sent in a patch to fix an issue sqlsmith uncovered in
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