Nouvelles hebdomadaires de PostgreSQL - 3 juin 2007
Les discussions se poursuivent avec vigueur à propos des nombreuses nouveautés à incorporer dans la 8.3.
Les nouveautés des produits dérivés
Jobs PostgreSQL en juin
http://archives.postgresql.org/pgsql-jobs/2007-06/threads.php
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PostgreSQL dans les média
Les PostgreSQL Weekly News vous sont présentées cette semaine par David Fetter. Adaptation francophone par la communauté PostgresqlFr.
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Correctifs appliqués
Andrew Dunstan a commité :
- Improve efficiency of LIKE/ILIKE code, especially for multi-byte charsets, and most especially for UTF8. Remove unnecessary special cases for bytea processing and single-byte charset ILIKE. a ILIKE b is now processed as lower(a) LIKE lower(b) in all cases. The code is now considerably simpler. All comparisons are now performed byte-wise, and the text and pattern are also advanced byte-wise where it is safe to do so - essentially where a wildcard is not being matched. Andrew Dunstan, from an original patch by ITAGAKI Takahiro, with ideas from Tom Lane and Mark Mielke.
Teodor Sigaev a commité :
- Replace ReadBuffer to ReadBufferWithStrategy in all vacuum-involved places to implement limited-size "ring" of buffers for VACUUM for GIN & GIST.
Peter Eisentraut a commité :
- Clarify some error messages about duplicate things.
- Make some messages more consistent.
- Downgrade some low-level startup messages to DEBUG1.
Bruce Momjian a commité :
- Remove description for now-complete TODO item: "-Add a GUC variable to control the tablespace for temporary objects and sort files."
- Updated TODO: "Allow free-behind capability for large sequential scans to avoid kernel cache spoiling."
- Update wording and add URL for TODO: "Research self-referential UPDATEs that see inconsistent row versions in read-committed mode."
- Wording improvement in FAQ_DEV.
- Update FAQ_DEV URL to output for text format.
- Add URL for code comments to developer's FAQ.
- Update TODO to read: "Consider allowing 64-bit integers and floats to be passed by value on 64-bit platforms Also change 32-bit floats (float4) to be passed by value at the same time."
- Add to TODO: "Consider allowing 64-bit integers to be passed by value on 64-bit platforms."
- Les Hill's patch which adds standard error redirection for OS/X & darwin startup script.
- Guillaume Cottenceau's patch which updates documentation to mention VACUUM FULL and CLUSTER where appropriate.
- Add URL for TODO: "Improve speed with indexes."
- Jim Nasby's patch which adds a documentation reference to statistical functions from func.sgml.
- Mark Cotner's patch to update /contrib OS/X startup files, and move to a separate OS/X directory.
- Update cvsutils documentation description.
- David Fetter's patch to update cvs instructions to suggest cvsutils.
- Fix trivial misspelling in comment.
- Add to TODO: "Fix self-referential UPDATEs that see inconsistent row versions in read-committed mode."
Tom Lane a commité :
- Create a GUC parameter temp_tablespaces that allows selection of the tablespace(s) in which to store temp tables and temporary files. This is a list to allow spreading the load across multiple tablespaces (a random list element is chosen each time a temp object is to be created). Temp files are not stored in per-database pgsql_tmp/ directories anymore, but per-tablespace directories. Jaime Casanova and Albert Cervera, with review by Bernd Helmle and Tom Lane.
- Fix erroneous error reporting for overlength input in text_date(), text_time(), and text_timetz(). 7.4-vintage bug found by Greg Stark.
- Fix aboriginal bug in BufFileDumpBuffer that would cause it to write the wrong data when dumping a bufferload that crosses a component-file boundary. This probably has not been seen in the wild because (a) component files are normally 1GB apiece and (b) non-block-aligned buffer usage is relatively rare. But it's fairly easy to reproduce a problem if one reduces RELSEG_SIZE in a test build. Kudos to Kurt Harriman for spotting the bug.
- Make CREATE/DROP/RENAME DATABASE wait a little bit to see if other backends will exit before failing because of conflicting DB usage. Per discussion, this seems a good idea to help mask the fact that backend exit takes nonzero time. Remove a couple of thereby-obsoleted sleeps in contrib and PL regression test sequences.
- Buy back some of the cycles spent in more-expensive hash functions by selecting power-of-2, rather than prime, numbers of buckets in hash joins. If the hash functions are doing their jobs properly by making all hash bits equally random, this is good enough, and it saves expensive integer division and modulus operations.
- Fix performance problems in multi-batch hash joins by ensuring that we select a well-randomized batch number even when given a poorly-randomized hash value. This is a bit inefficient but seems the only practical solution given the constraint that we can't change the hash functions in released branches. Per report from Joseph Shraibman. Applied to 8.1 and 8.2 only --- HEAD is getting a cleaner fix, and 8.0 and before use different coding that seems less vulnerable.
- Fix several hash functions that were taking chintzy shortcuts instead of delivering a well-randomized hash value. I got religion on this after observing that performance of multi-batch hash join degrades terribly if the higher-order bits of hash values aren't random, as indeed was true for say hashes of small integer values. It's now expected and documented that hash functions should use hash_any or some comparable method to ensure that all bits of their output are about equally random. initdb forced because this change invalidates existing hash indexes. For the same reason, this isn't back-patchable; the hash join performance problem will get a band-aid fix in the back branches.
- The shortcut exit that I recently added to ExecInitIndexScan() for EXPLAIN-only operation was a little too short; it skipped initializing the node's result tuple type, which may be needed depending on what's above the indexscan node. Call ExecAssignResultTypeFromTL before exiting. (For good luck I moved up the ExecAssignScanProjectionInfo call as well, so that everything except indexscan-specific initialization will still be done.) Per example from Grant Finnemore.
- Change build_index_pathkeys() so that the expressions it builds to represent index key columns always have the type expected by the index's associated operators, ie, we add RelabelType nodes when dealing with binary-compatible index opclasses. This is needed to get varchar indexes to play nicely with the new EquivalenceClass machinery, as per recent gripe from Josh Berkus that CVS HEAD was failing to match a varchar index column to a constant restriction in the query. It seems likely that this change will allow removal of a lot of ugly ad-hoc RelabelType-stripping that the planner has traditionally done while matching expressions to other expressions, but I'll worry about that some other day.
- Fix overly-strict sanity check in BeginInternalSubTransaction that made it fail when used in a deferred trigger. Bug goes back to 8.0; no doubt the reason it hadn't been noticed is that we've been discouraging use of user-defined constraint triggers. Per report from Frank van Vugt.
- Make large sequential scans and VACUUMs work in a limited-size "ring" of buffers, rather than blowing out the whole shared-buffer arena. Aside from avoiding cache spoliation, this fixes the problem that VACUUM formerly tended to cause a WAL flush for every page it modified, because we had it hacked to use only a single buffer. Those flushes will now occur only once per ring-ful. The exact ring size, and the threshold for seqscans to switch into the ring usage pattern, remain under debate; but the infrastructure seems done. The key bit of infrastructure is a new optional BufferAccessStrategy object that can be passed to ReadBuffer operations; this replaces the former StrategyHintVacuum API. This patch also changes the buffer usage-count methodology a bit: we now advance usage_count when first pinning a buffer, rather than when last unpinning it. To preserve the behavior that a buffer's lifetime starts to decrease when it's released, the clock sweep code is modified to not decrement usage_count of pinned buffers. Work not done in this commit: teach GiST and GIN indexes to use the vacuum BufferAccessStrategy for vacuum-driven fetches. Original patch by Simon, reworked by Heikki and again by Tom.
- Tweak the code in a couple of places to try to deliver more user-friendly error messages when a single COPY line is too long for us to handle. Per example from Johann Spies.
Neil Conway a commité :
- Remove incorrect semicolon in example. This was previously fixed in HEAD only -- backporting to 8.2. Per report from Frank van Vugt.
- Allow leading and trailing whitespace in the input to the boolean type. Also, add explicit casts between boolean and text/varchar. Both of these changes are for conformance with SQL:2003. Update the regression tests, bump the catversion.
- Tweak: use memcpy() in text_time(), rather than manually copying bytes in a loop.
- Fix a bug in input processing for the "interval" type. Previously, "microsecond" and "millisecond" units were not considered valid input by themselves, which caused inputs like "1 millisecond" to be rejected erroneously. Update the docs, add regression tests, and backport to 8.2 and 8.1
- mmgr README tweak: "either" is no longer correct. The previous wording compared PortalContext with QueryContext, but the latter no longer exists.
- Stop a few regression tests from needlessly disabling GEQO. This was necessary in 1997, when geqo_threshold did not exist, but it is no longer needed.
- Code cleanup: use "bool" for Boolean variables, rather than "int".
Michael Meskes a commité :
- Applied patch send by Joachim Wieland to fix INTEGER_DATETIMES under MSVC.
- Applied Joachim Wieland's patch for ecpg_config.h creation on Vista. Changed variable test to not run into infinite loops on backend errors.