== PostgreSQL Weekly News - August 19 2007 ==

== PostgreSQL Weekly News - August 19 2007 ==

== PostgreSQL Product News ==

Once:radix 0.9 released.
http://sourceforge.net/projects/onceradix/

pgAdmin III 1.8.0 Beta 3 released.
http://www.pgadmin.org/

pgUnitTest released:
http://pgfoundry.org/projects/pgunittest

== PostgreSQL Jobs for August ==

http://archives.postgresql.org/pgsql-jobs/2007-08/threads.php

== PostgreSQL Local ==

== PostgreSQL in the News ==

Planet PostgreSQL: http://www.planetpostgresql.org/

General Bits, Archives and occasional new articles:
http://www.varlena.com/GeneralBits/

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@fetter.org, German to
pwn@pgug.de.


== Applied Patches ==

Andrew Dunstan committed:

- Fix minor typo fixes in CSVlog docs, per Michael Glaesemann.

- Provide for logfiles in machine readable CSV format. In consequence,
  rename redirect_stderr to logging_collector.  Original patch from
  Arul Shaji, subsequently modified by Greg Smith, and then heavily
  modified by me.

Bruce Momjian committed:

- Mark TODO as DONE: "Allow server log information to be output as CSV
  format."

- Add to TODO, with URL reference, "Reduce XID consumption of
  read-only queries."

- Add another idea to TODO item, "Allow data to be pulled directly
  from indexes."

- Fix whitespace in TODO.

- Mark TODO as DONE: "Use backend PREPARE/EXECUTE facility for ecpg
  where possible."

Micheal Meskes committed:

- In pgsql/src/interfaces/ecpg/test/expected, it seems we simply
  expected the same output for failure and success.

- Hopefully fixed missing CHAR_BIT symbol in ecpg.

- Fixed compiler warning for enum handling in ecpg.

- Finished major rewrite to use new protocol version for ecpg.  Really
  prepare statements.  Added more regression tests.  Added
  auto-prepare mode.  Use '$n' for positional variables, '?' is still
  possible via ecpg option.  Cleaned up the sources a little bit.

Tom Lane committed:

- Arrange to cache a ResultRelInfo in the executor's EState for
  relations that are not one of the query's defined result relations,
  but nonetheless have triggers fired against them while the query is
  active.  This was formerly impossible but can now occur because of
  my recent patch to fix the firing order for RI triggers.  Caching a
  ResultRelInfo avoids duplicating work by repeatedly opening and
  closing the same relation, and also allows EXPLAIN ANALYZE to "see"
  and report on these extra triggers.  Use the same mechanism to cache
  open relations when firing deferred triggers at transaction
  shutdown; this replaces the former one-element-cache strategy used
  in that case, and should improve performance a bit when there are
  deferred triggers on a number of relations.

- Repair problems occurring when multiple RI updates have to be done
  to the same row within one query: we were firing check triggers
  before all the updates were done, leading to bogus failures.  Fix by
  making the triggers queued by an RI update go at the end of the
  outer query's trigger event list, thereby effectively making the
  processing "breadth-first".  This was indeed how it worked pre-8.0,
  so the bug does not occur in the 7.x branches.  Per report from
  Pavel Stehule.

- Fix oversight in async-commit patch: there were some places in
  heapam.c that still thought they could set HEAP_XMAX_COMMITTED
  immediately after seeing the other transaction commit.  Make them
  use the same logic as tqual.c does to determine if the hint bit can
  be set yet.

- TEMPORARILY make synchronous_commit default to OFF, so that we can
  get more thorough testing of async-commit mode from the buildfarm.
  This patch MUST get reverted before 8.3 release!

- Fix two bugs induced in VACUUM FULL by async-commit patch.  First,
  we cannot assume that XLogAsyncCommitFlush guarantees hint bits will
  be settable, because clog.c's inexact LSN bookkeeping results in
  windows where a previously flushed transaction is considered
  unhintable because it shares an LSN slot with a later unflushed
  transaction.  But repair_frag requires XMIN_COMMITTED to be correct
  so that it can distinguish tuples moved by the current vacuum.
  Since not being able to set the bit is an uncommon corner case, the
  most practical way of dealing with it seems to be to abandon
  shrinking (ie, don't invoke repair_frag) when we find a non-dead
  tuple whose XMIN_COMMITTED bit couldn't be set.  Second, it is
  possible for the same reason that a RECENTLY_DEAD tuple does not get
  its XMAX_COMMITTED bit set during scan_heap.  But by the time
  repair_frag examines the tuple it might be possible to set the bit.
  We therefore must take buffer content lock when calling
  HeapTupleSatisfiesVacuum a second time, else we can get an Assert
  failure in SetBufferCommitInfoNeedsSave.  This latter bug is latent
  in existing releases, but I think it cannot actually occur without
  async commit, since the first HeapTupleSatisfiesVacuum call should
  always have set the bit.  So I'm not going to back-patch it.  In
  passing, reduce the existing "cannot shrink relation" messages from
  NOTICE to LOG level.  The new message must be no higher than LOG if
  we don't want unpredictable regression test failures, and
  consistency seems like a good idea.  Also arrange that only one such
  message is reported per VACUUM FULL; in typical scenarios you could
  get spammed with many such messages, which seems a bit useless.

- Document that the regexp split functions ignore zero-length matches
  in certain corner cases.  Per discussion, the code does what we
  want, but it really needs to be documented that these functions act
  differently from regexp_matches.

- Remove an "optimization" I installed in 2001, to make repalloc()
  attempt to enlarge the memory chunk in-place when it was feasible to
  do so.  This turns out to not work well at all for scenarios
  involving repeated cycles of palloc/repalloc/pfree: the eventually
  freed chunks go into the wrong freelist for the next initial palloc
  request, and so we consume memory indefinitely.  While that could be
  defended against, the number of cases where the optimization can
  still be applied drops significantly, and adjusting the initial
  sizes of StringInfo buffers makes it drop to almost nothing.  Seems
  better to just remove the extra complexity.  Per recent discussion
  and testing.

- Increase the initial size of StringInfo buffers to 1024 bytes (from
  256); likewise increase the initial size of the scanner's literal
  buffer to 1024 (from 128).  Instrumentation of the regression tests
  suggests that this saves a useful amount of repalloc() traffic ---
  the number of calls occurring during one set of tests drops from
  about 6900 to about 3900.  The old sizes were chosen in the late
  90's with an eye to machines much smaller than are common today.

== Rejected Patches (for now) ==

Brendan Jurd's patch which refactors formatting.c, pushed out to 8.4.

ITAGAKI Takahiro's patch which reduces the size of PageFreeSpaceInfo
on 64bit platforms.  The patch didn't touch enough places.

== Pending Patches ==

Zdenek Kotala sent in another version of his pgcrypto patch.

Julius Stroffek sent in another version of his patch for optimizer
hooks.

Peter Eisentraut sent in a patch to enable people to use their
system's time zone files.

Merlin Moncure sent in a patch which adds a pgparam extension to the
libpq api.