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== PostgreSQL Weekly News - June 24 2012 ==

From: David Fetter <david(at)fetter(dot)org>
To: PostgreSQL Announce <pgsql-announce(at)postgresql(dot)org>
Subject: == PostgreSQL Weekly News - June 24 2012 ==
Date: 2012-06-25 03:47:20
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Lists: pgsql-announce
== PostgreSQL Weekly News - June 24 2012 ==

The Commitfest Continues.  You can help!

== PostgreSQL Jobs for June ==

== PostgreSQL Local ==

The CfP for Postgres Open 2012 September 17-19 in Chicago is open.
Submissions are due by 11:59pm, June 26, 2012.

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:

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)

== Reviews ==

== Applied Patches ==

Tom Lane pushed:

- Change ON UPDATE SET NULL/SET DEFAULT referential actions to meet
  SQL spec.  Previously, when executing an ON UPDATE SET NULL or SET
  DEFAULT action for a multicolumn MATCH SIMPLE foreign key
  constraint, we would set only those referencing columns
  corresponding to referenced columns that were changed.  This is what
  the SQL92 standard said to do --- but more recent versions of the
  standard say that all referencing columns should be set to null or
  their default values, no matter exactly which referenced columns
  changed.  At least for SET DEFAULT, that is clearly saner behavior.
  It's somewhat debatable whether it's an improvement for SET NULL,
  but it appears that other RDBMS systems read the spec this way.  So
  let's do it like that.  This is a release-notable behavioral change,
  although considering that our documentation already implied it was
  done this way, the lack of complaints suggests few people use such

- Update SQL spec references in ri_triggers code to match SQL:2008.
  Now that what we're implementing isn't SQL92, we probably shouldn't
  cite chapter and verse in that spec anymore.  Also fix some comments
  that talked about MATCH FULL but in fact were in code that's also
  used for MATCH SIMPLE.  No code changes in this commit, just

- Remove derived fields from RI_QueryKey, and do a bit of other
  cleanup.  We really only need the foreign key constraint's OID and
  the query type code to uniquely identify each plan we are caching
  for FK checks.  The other stuff that was in the struct had no
  business being used as part of a hash key, and was all just being
  copied from struct RI_ConstraintInfo anyway.  Get rid of the
  unnecessary fields, and readjust various function APIs to make them
  use RI_ConstraintInfo not RI_QueryKey as info source.  I'd be
  surprised if this makes any measurable performance difference, but
  it certainly feels cleaner.

- Allow ON UPDATE/DELETE SET DEFAULT plans to be cached.  Once upon a
  time, somebody was worried that cached RI plans wouldn't get remade
  with new default values after ALTER TABLE ... SET DEFAULT, so they
  didn't allow caching of plans for ON UPDATE/DELETE SET DEFAULT
  actions.  That time is long gone, though (and even at the time I
  doubt this was the greatest hazard posed by ALTER TABLE...).  So
  allow these triggers to cache their plans just like the others.  The
  cache_plan argument to ri_PlanCheck is now vestigial, since there
  are no callers that don't pass "true"; but I left it alone in case
  there is any future need for it.

- Improve comments about why SET DEFAULT triggers must recheck for
  matches.  I was confused about this, so try to make it clearer for
  the next person.  (This seems like a fairly inefficient way of
  dealing with a corner case, but I don't have a better idea offhand.
  Maybe if there were a way to turn off the RI_FKey_keyequal_upd_fk
  event filter temporarily?)

- Share RI trigger code between NO ACTION and RESTRICT cases.  These
  triggers are identical except for whether ri_Check_Pk_Match is to be
  called, so factor out the common code to save a couple hundred
  lines.  Also, eliminate null-column checks in ri_Check_Pk_Match,
  since they're duplicate with the calling functions and require
  unnecessary complication in its API statement.  Simplify the way
  code is shared between RI_FKey_check_ins and RI_FKey_check_upd, too.

- Add pgbench option to add foreign key constraints to the standard
  scenario.  The option --foreign-keys, used at initialization time,
  will create foreign key constraints for the columns that represent
  references to other tables' primary keys.  This can help in
  benchmarking FK performance.  Jeff Janes

- Improve tests for whether we can skip queueing RI enforcement
  triggers.  During an update of a PK row, we can skip firing the RI
  trigger if any old key value is NULL, because then the row could not
  have had any matching rows in the FK table.  Conversely, during an
  update of an FK row, the outcome is determined if any new key value
  is NULL.  In either case it becomes unnecessary to compare
  individual key values.  This patch was inspired by discussion of Vik
  Reykja's patch to use IS NOT DISTINCT semantics for the key
  comparisons.  In the event there is no need for that and so this
  patch looks nothing like his, but he should still get credit for
  having re-opened consideration of the trigger skip logic.

- Cache the results of ri_FetchConstraintInfo in a backend-local
  cache.  Extracting data from pg_constraint turned out to take as
  much as 10% of the runtime in a bulk-update case where the foreign
  key column wasn't changing, because we did it over again for each
  tuple.  Fix that by maintaining a backend-local cache of the
  results.  This is really a pretty small patch, but converting the
  trigger functions to work with pointers rather than local struct
  variables requires a lot of mechanical changes.

- Increase MAX_SYSCACHE_CALLBACKS from 20 to 32.  By my count there
  are 18 callers of CacheRegisterSyscacheCallback in the core code in
  HEAD, so we are potentially leaving as few as 2 slots for any add-on
  code to use (though possibly not all these callers would actually
  activate in any particular session).  That doesn't seem like a lot
  of headroom, so let's pump it up a little.

- Remove incomplete/incorrect support for zero-column foreign keys.
  The original coding in ri_triggers.c had partial support for the
  concept of zero-column foreign key constraints.  But this is not
  defined in the SQL standard, nor was it ever allowed by any other
  part of Postgres, nor was it very fully implemented even here (eg
  there was no support for preventing PK-table deletions that would
  violate the constraint).  Doesn't seem very useful to carry 100-plus
  lines of code for a corner case that no one is interested in making
  work.  Instead, just add a check that the column list read from
  pg_constraint is non-empty.

- Fix memory leak in ARRAY(SELECT ...) subqueries.  Repeated execution
  of an uncorrelated ARRAY_SUBLINK sub-select (which I think can only
  happen if the sub-select is embedded in a larger, correlated
  subquery) would leak memory for the duration of the query, due to
  not reclaiming the array generated in the previous execution.  Per
  bug #6698 from Armando Miraglia.  Diagnosis and fix idea by Heikki,
  patch itself by me.  This has been like this all along, so
  back-patch to all supported versions.

Peter Eisentraut pushed:

- Remove confusing half sentence from legal notice.  Pointed out by
  Stefan Kaltenbrunner

- Make placeholders in SQL command help more consistent and precise.
  To avoid divergent names on related pages, avoid ambiguities, and
  reduce translation work a little.

- Replace int2/int4 in C code with int16/int32.  The latter was
  already the dominant use, and it's preferable because in C the
  convention is that intXX means XX bits.  Therefore, allowing mixed
  use of int2, int4, int8, int16, int32 is obviously confusing.
  Remove the typedefs for int2 and int4 for now.  They don't seem to
  be widely used outside of the PostgreSQL source tree, and the few
  uses can probably be cleaned up by the time this ships.

- Update copyright year in forgotten places.  Found by Stefan

- pg_dump: Add missing newlines at end of messages

Alvaro Herrera pushed:

- pg_dump: Fix verbosity level in LO progress messages.  In passing,
  reword another instance of the same message that was gratuitously
  different.  Author: Josh Kupershmidt after a bug report by Bosco

- Repair comment mangled by a pgindent run long ago.

Heikki Linnakangas pushed:

- Add a small cache of locks owned by a resource owner in
  ResourceOwner.  This speeds up reassigning locks to the parent
  owner, when the transaction holds a lot of locks, but only a few of
  them belong to the current resource owner. This is particularly
  helps pg_dump when dumping a large number of objects.  The cache can
  hold up to 15 locks in each resource owner. After that, the cache is
  marked as overflowed, and we fall back to the old method of scanning
  the whole local lock table. The tradeoff here is that the cache has
  to be scanned whenever a lock is released, so if the cache is too
  large, lock release becomes more expensive. 15 seems enough to cover
  pg_dump, and doesn't have much impact on lock release.  Jeff Janes,
  reviewed by Amit Kapila and Heikki Linnakangas.

- Move WAL continuation record information to WAL page header.  The
  continuation record only contained one field, xl_rem_len, so it
  makes things simpler to just include it in the WAL page header. This
  wastes four bytes on pages that don't begin with a continuation from
  previos page, plus four bytes on every page, because of padding.
  The motivation of this is to make it easier to calculate how much
  space a WAL record needs. Before this patch, it depended on how many
  page boundaries the record crosses. The motivation of that, in turn,
  is to separate the allocation of space in the WAL from the copying
  of the record data to the allocated space. Keeping the calculation
  of space required simple helps to keep the critical section of
  allocating the space from WAL short. But that's not included in this
  patch yet.  Bump WAL version number again, as this is an
  incompatible change.

- Don't waste the last segment of each 4GB logical log file.  The
  comments claimed that wasting the last segment made it easier to do
  calculations with XLogRecPtrs, because you don't have problems
  representing last-byte-position-plus-1 that way. In my experience,
  however, it only made things more complicated, because the there was
  two ways to represent the boundary at the beginning of a logical log
  file: logid = n+1 and xrecoff = 0, or as xlogid = n and xrecoff =
  4GB - XLOG_SEG_SIZE. Some functions were picky about which
  representation was used.  Also, use a 64-bit segment number instead
  of the log/seg combination, to point to a certain WAL segment. We
  assume that all platforms have a working 64-bit integer type
  nowadays.  This is an incompatible change in WAL format, so bumping
  WAL version number.

- Replace XLogRecPtr struct with a 64-bit integer.  This simplifies
  code that needs to do arithmetic on XLogRecPtrs.  To avoid changing
  on-disk format of data pages, the LSN on data pages is still stored
  in the old format. That should keep pg_upgrade happy.  However, we
  have XLogRecPtrs embedded in the control file, and in the structs
  that are sent over the replication protocol, so this changes breaks
  compatibility of pg_basebackup and server. I didn't do anything
  about this in this patch, per discussion on -hackers, the right
  thing to do would to be to change the replication protocol to be
  architecture-independent, so that you could use a newer version of
  pg_receivexlog, for example, against an older server version.

- Allow WAL record header to be split across pages.  This saves a few
  bytes of WAL space, but the real motivation is to make it
  predictable how much WAL space a record requires, as it no longer
  depends on whether we need to waste the last few bytes at end of WAL
  page because the header doesn't fit.  The total length field of WAL
  record, xl_tot_len, is moved to the beginning of the WAL record
  header, so that it is still always found on the first page where a
  WAL record begins.  Bump WAL version number again as this is an
  incompatible change.

- Use LL suffix for 64-bit constants.  Per warning from buildfarm
  member 'locust'. At least I think this what's making it upset.

- Oops.  Remove stray paren.  I didn't notice this on my laptop as I

- Use UINT64CONST for 64-bit integer constants.  Peter Eisentraut
  advised me that UINT64CONST is the proper way to do that, not LL

- I missed some references to xlogid/xrecoff in Win32-only code. Fix.

Robert Haas pushed:

- Document that && can be used to search arrays.  Also, add some
  cross-links to the indexing documentation, so it's easier to notice
  that && and other array operators have index support.  Ryan Kelly,
  edited by me.

- Make pgbench -i emit only one-tenth as many status messages.  These
  days, even a wimpy system can insert 10000 tuples in the blink of an
  eye, so there's no real need for this much verbosity.  Per complaint
  from Tatsuo Ishii.

== Rejected Patches (for now) ==

No one was disappointed this week :-)

== Pending Patches ==

Joachim Wieland sent in another revision of the patch to implement
parallel pg_dump.

Robert Haas sent in another revision of the patch to avoid heavyweight
locking on hash metapages.

Kyotaro HORIGUCHI sent in another revision of the patch to skip
checkpoint on promoting from streaming replication.

Jeff Davis sent in two more revisions of the patch to fix fsync
behavior on initdb.

Alexander Korotkov sent in a patch to reduce gistchoose index bloat.

Zoltan Boszormenyi sent in four more revisions of the patch to
implement lock_timeout and SIGALARM framework.

Peter Eisentraut sent in another revision of the patch to prevent
sub-main functions in the backend from returning anything.

Honza Horak sent in another revision of the patch to allow PostgreSQL
to answer on more than one Unix socket.

Alvaro Herrera and Kyotaro HORIGUCHI traded patches to fix PL/Perl in
SQL_ASCII-encoded databases.

Greg Smith sent in a patch to try to avoid running with a full fsync
request queue.

Robert Haas sent in a patch to make pgbench less yappy.

Peter Eisentraut sent in a patch to revive AC_PROG_INSTALL.

John Lumby sent in a patch intended to enable using INSERT ...
RETURNING in a RULE on a partitioned table.

Alexander Korotkov sent in a patch to fix an issue with GiST indexing
on points.

Alexander Korotkov sent in another revision of the patch for SP-GiST
for ranges, this time using a k-d tree instead of quad-tree.

Kevin Grittner and Alvaro Herrera traded patches to implement foreign
key locks.

Tom Lane sent in another revision of the patch to fix pg_dump
dependencies in the --section case.

Dimitri Fontaine sent in another revision of the event trigger patch.

David Kerr sent in a patch to allow using an empty backup_label in
streaming replication.

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