PostgreSQL 2008年4月第3周新闻综述 -- 2008/04/20

From PostgreSQL 中文维基, PostgreSQL 中文站, PostgreSQL 中国社区, PostgreSQL Chinese community

最近又有很多新的补丁已提交至-patch邮件列表。

PostgreSQL在FISL第九届开源软件大会的设展又获得了很大成功，这次会议上又新增了新的培训机构，看到了一些新面孔的员工，一些新的政策也在执行。本次开源大会约有7500人参加，这也使得FISL成为世界上最大规模的开源软件大会。

[编辑] PostgreSQL相关软件新闻

Archiveopteryx 2.08 版本发布，详情可浏览：http://www.archiveopteryx.org/2.08

Federico (rotellaro) Campoli公司有关PITR备份恢复的培训课程将在2008/06/09举行仪，详情可浏览：http://www.pghost.eu/node/59

[编辑] PostgreSQL 四月相关工作机会

详情可浏览：http://archives.postgresql.org/pgsql-jobs/2008-04/threads.php

[编辑] PostgreSQL各地新闻

PostgreSQL Day Unicamp 2008 will be on April 22 in Campinas, SP, Brazil. http://www.dextra.com.br/dia-postgresql.htm

企业数据库2008年会将于4/24--25在莫斯科举行，详情可浏览：http://citforum.ru/seminars/cbd2008/

PGCon 2008年度大会将于05/20--23在渥太华举行，详情可浏览：http://www.pgcon.org/2008/

PostgreSQL日将在开源大会(OSCON)之前于波特兰举行，详情可浏览：http://pugs.postgresql.org/taxonomy/term/53

犹他州2008开源软件大会自6/1起开放注册，这个第二次的年度大会将于2008/08/28--30日在Salt Lake举行，详情可浏览：http://2008.utosc.com/

[编辑] PostgreSQL其他新闻

PostgreSQL网志站点：http://www.planetpostgresql.org/

PostgreSQL技巧站点，目前主要为一些存档文章和很少的更新：http://www.varlena.com/GeneralBits/

PostgreSQL本周新闻综述是由David Fetter带给我们大家的，谢谢他的工作。

如果您想提交一些新闻或是软件发布稿等内容可在每周星期天的下午3:00（太平洋时区）前，英文版的内容可发送至david@fetter.org，德文版本的内容可发送至pwn@pgug.de，意大利语版本的内容可发至pwn@itpug.org

[编辑] 本周打入系统的补丁

Tom Lane committed:

- Push index operator lossiness determination down to GIST/GIN opclass "consistent" functions, and remove pg_amop.opreqcheck, as per recent discussion. The main immediate benefit of this is that we no longer need 8.3's ugly hack of requiring @@@ rather than @@ to test weight-using tsquery searches on GIN indexes. In future it should be possible to optimize some other queries better than is done now, by detecting at runtime whether the index match is exact or not. Tom Lane, after an idea of Heikki Linnakangas's, and with some help from Teodor Sigaev.

- In pgsql/src/backend/utils/cache/relcache.c, fix LOAD_CRIT_INDEX() macro to take out AccessShareLock on the system index it is trying to build a relcache entry for. This is an oversight in my 8.2 patch that tried to ensure we always took a lock on a relation before trying to build its relcache entry. The implication is that if someone committed a reindex of a critical system index at about the same time that some other backend were starting up without a valid pg_internal.init file, the second one might PANIC due to not seeing any valid version of the index's pg_class row. Improbable case, but definitely not impossible.

- Repair two places where SIGTERM exit could leave shared memory state corrupted. (Neither is very important if SIGTERM is used to shut down the whole database cluster together, but there's a problem if someone tries to SIGTERM individual backends.) To do this, introduce new infrastructure macros PG_ENSURE_ERROR_CLEANUP/PG_END_ENSURE_ERROR_CLEANUP that take care of transiently pushing an on_shmem_exit cleanup hook. Also use this method for createdb cleanup --- that wasn't a shared-memory-corruption problem, but SIGTERM abort of createdb could leave orphaned files lying around. Backpatch as far as 8.2. The shmem corruption cases don't exist in 8.1, and the createdb usage doesn't seem important enough to risk backpatching further.

- In pgsql/src/backend/commands/explain.c, add some code to EXPLAIN to show the targetlist (ie, output columns) of each plan node. For the moment this is debug support only and is not enabled unless EXPLAIN_PRINT_TLISTS is defined at build time. Later I'll see about the idea of letting EXPLAIN VERBOSE do it.

- Fix a couple of oversights associated with the "physical tlist" optimization: we had several code paths where a physical tlist could be used for the input to a Sort node, which is a dumb idea because any unneeded table columns will increase the volume of data the sort has to push around. (Unfortunately the easy-looking fix of calling disuse_physical_tlist during make_sort_xxx doesn't work because in most cases we're already committed to the current input tlist --- it's been marked with sort column numbers, or we've built grouping column numbers using it, etc. The tlist has to be selected properly at the calling level before we start constructing sort-col information. This is easy enough to do, we were just failing to take the point into consideration.) Back-patch to 8.3. I believe the problem probably exists clear back to 7.4 when the physical tlist optimization was added, but I'm afraid to back-patch further than 8.3 without a great deal more study than I want to put into it. The code in this area has drifted a lot over time. The real-world importance of these code paths is uncertain anyway --- I think in many cases we'd probably prefer hash-based methods.

- Cause EXPLAIN's VERBOSE option to print the target list (output column list) of each plan node, instead of its former behavior of dumping the internal representation of the plan tree. The latter display is still available for those who really want it (see debug_print_plan), but uses for it are certainly few and and far between. Per discussion. This patch also removes the explain_pretty_print GUC, which is obsoleted by the change.

- Fix rmtree() so that it keeps going after failure to remove any individual file; the idea is that we should clean up as much as we can, even if there's some problem removing one file. Make the error messages a bit less misleading, too. In passing, const-ify function arguments.

- Fix typo in pgsql/contrib/seg/uninstall_seg.sql.

- In pgsql/contrib/seg/seg.c, seg_size() has to be V1 calling convention, too.

- In pgsql/contrib/earthdistance/earthdistance.c, convert earthdistance's only C function to v1 call convention, to future-proof it against pass-by-value float8.

- Allow float8, int8, and related datatypes to be passed by value on machines where Datum is 8 bytes wide. Since this will break old-style C functions (those still using version 0 calling convention) that have arguments or results of these types, provide a configure option to disable it and retain the old pass-by-reference behavior. Likewise, provide a configure option to disable the recently-committed float4 pass-by-value change. Zoltan Boszormenyi, plus configurability stuff by me.

- Make earthdistance use version-0 calling convention if not USE_FLOAT8_BYVAL, and version-1 if USE_FLOAT8_BYVAL. This might seem a bit pointless, but the idea is to have at least one regression test that will fail if we ever accidentally break version-0 functions that return float8. However, they're already broken, or at least hopelessly unportable, in the USE_FLOAT8_BYVAL case. Per a recent suggestion from Greg Stark.

- In pgsql/src/include/pg_config.h.win32, add FLOAT4PASSBYVAL/FLOAT8PASSBYVAL to pg_config.h.win32, as a stopgap measure to get the Windows buildfarm members working again. I don't know if it's worth exposing these as configurables, or exactly how to do it in the MSVC build system ...

- In pgsql/src/backend/executor/execMain.c, fix a couple of places in execMain that erroneously assumed that SELECT FOR UPDATE/SHARE couldn't occur as a subquery in a query with a non-SELECT top-level operation. Symptoms included outright failure (as in report from Mark Mielke) and silently neglecting to take the requested row locks. Back-patch to 8.3, because the visible failure in the INSERT ... SELECT case is a regression from 8.2. I'm a bit hesitant to back-patch further given the lack of field complaints.

Alvaro Herrera committed:

- In pgsql/src/bin/psql/describe.c, fix indentation in new REFERENCED BY psql output, per Brendan Jurd.

- Clean up a few places where Datums were being treated as pointers (and vice versa) without going through DatumGetPointer. Gavin Sherry, with Feng Tian.

- Modify the float4 datatype to be pass-by-val. Along the way, remove the last uses of the long-deprecated float32 in contrib/seg; the definitions themselves are still there, but no longer used. fmgr/README updated to match. I added a CREATE FUNCTION to account for existing seg_center() code in seg.c too, and some tests for it and the neighbor functions. At the same time, remove checks for NULL which are not needed (because the functions are declared STRICT). I had to do some adjustments to contrib's btree_gist too. The choices for representation there are not ideal for changing the underlying types :-( Original patch by Zoltan Boszormenyi, with some adjustments by me.

- In pgsql/contrib/seg/seg.c, change the float4-returning functions in contrib/seg to fmgr v1 calling conventions. I also changed seg_in and seg_out, which was probably unnecessary, but it can't harm.

Bruce Momjian committed:

- Add URL for TODO: "Consider automatic caching of statements at various levels."

- Add pg_terminate_backend() to allow terminating only a single session.

- Mark TODO as DONE: "Allow administrators to safely terminate individual sessions."

- Add to TODO: "Allow XML to accept more liberal DOCTYPE specifications."

- Move LISTEN/NOTIFY items to separate TODO section.

- Split TODO into two items: "Allow NOTIFY in rules involving conditionals" and "Improve LISTEN concurrency."

- Revert addition of pg_terminate_backend() because of race conditions. Unmark TODO.

- Re-add terminate TODO item.

- Add to TODO: "Implement the non-threaded Avahi service discovery protocol."

- Update TODO wording on psql.

- In pgsql/src/bin/psql/mbprint.c, fix comment typo. Bryce Nesbitt.

- In FAQ, update most recent release to 8.3.1.

- In pgsql/src/tools/pgindent/pgindent, ignore blank lines in typedef file.

- Re-enable pg_terminate_backend() using SIGTERM. SIGTERM testing still needed.

- Mark TODO as DONE: "Allow administrators to safely terminate individual sessions."

- Remove TODO.detail references; instead add TODO URLs pointing to the archives. We have been using URLs for a while for new items.

- Remove TODO.detail directory. All URLs now in TODO file as references.

- Update TODO using new script.

- Add TODO2html tool to convert TODO to HTML.

- Add script FAQ2txt to convert HTML files to txt. Add comment to TODO2html.

- Update doc script comments.

Andrew Dunstan committed:

- Make integer_datetimes the default for MSVC even if not mentioned in config.pl.

- In pgsql/src/tools/msvc/Project.pm, add multi-line flag to regex that needs it. Backpatch to 8.2. Fix from Andreas Zeugswetter.

- Avoid using unnecessary pgwin32_safestat in libpq.

- Fix MinGW warnings re: formats and unused variables. Per ITAGAKI Takahiro.

Heikki Linnakangas committed:

- Fix two race conditions between the pending unlink mechanism that was put in place to prevent reusing relation OIDs before next checkpoint, and DROP DATABASE. First, if a database was dropped, bgwriter would still try to unlink the files that the rmtree() call by the DROP DATABASE command has already deleted, or is just about to delete. Second, if a database is dropped, and another database is created with the same OID, bgwriter would in the worst case delete a relation in the new database that happened to get the same OID as a dropped relation in the old database. To fix these race conditions: 1. make rmtree() ignore ENOENT errors. This fixes the 1st race condition. 2. make ForgetDatabaseFsyncRequests forget unlink requests as well. 3. force checkpoint on in dropdb on all platforms Since ForgetDatabaseFsyncRequests() is asynchronous, the 2nd change isn't enough on its own to fix the problem of dropping and creating a database with same OID, but forcing a checkpoint on DROP DATABASE makes it sufficient. Per Tom Lane's bug report and proposal. Backpatch to 8.3.

Teodor Sigaev committed:

- In pgsql/src/backend/utils/adt/tsquery_gist.c, fix broken compare function for tsquery_ops. Per Tom Lane's report. I never understood why initial authors GiST in pgsql choose so stgrange signature for 'same' method: bool *sameFn(Datum a, Datum b, bool* result) instead of simple, logical bool sameFn(Datum a, Datum b) This change will break any existing GiST extension, so we still live with it and will live.

[编辑] 暂未通过审核的补丁

Brendan Jurd sent in another revision of his printTable API.

Alvaro Herrera sent in another revision of his patch to track ActiveSnapshot.

Bruce Momjian and Bryce Nesbitt updated Bryce Nesbitt's patch in several iterations. The patch optionally sets a maximum width for psql output and wraps the overflow.

Brendan Jurd sent in a new revision of his patch to show INHERIT in \du.

Brendan Jurd sent in a new revision of his patch to add conversions Text <-> C string.

Tom Lane sent in a WIP patch to remove lossy-operator RECHECK flags in some places.

Teodor Sigaev sent in another revision of a patch which implements partial match in GIN indexes.

Merlin Moncure sent in a patch to add hooks for the libpqtypes proposal.

ITAGAKI Takahiro sent in a patch which sorts writes during a checkpoint.

Brendan Jurd sent in a patch to remove the typename field from A_Const.

Merlin Moncure sent in a patch to add PQmakeResult, PQsetValue and PQresultAlloc to libpq.

Andrew Chernow sent in two revisions of his libpq object hooks patch.

Pavel Stehule sent in a patch which adds new options (SQLSTATE, DETAIL, DETAIL_LOG and HINT) to PL/PgSQL's RAISE statement.

Alex Hunsaker sent in a revised version of Joshua Drake's patch which adds a command line option --use-statement-timeout to pg_dump and pg_restore.

Brendan Jurd sent in two revisions of a patch which makes \z privileges multi-line in psql.