mysql5.1新特性--misc1

cocolala

1, external-locking

# Enable external file level locking. Enabled file locking will have a
# negative impact on performance, so only use it in case you have
# multiple database instances running on the same files (note some
# restrictions still apply!) or if you use other software relying on
# locking MyISAM tables on file level.
#external-locking

--看来mysql也可以做到像oracle一样，由多个实例访问同一份数据文件
--通过外部的file lock来实现，会降低性能

When MySQL is compiled using MIT-pthreads, system locking is disabled by default for performance reasons. You can tell the server to use system locking with the --external-locking option. This is needed only if you want to be able to run two MySQL servers against the same data files, but that is not recommended, anyway.


2, 从源码编译二进制文件时重新configure的注意事项
The solution to many problems involves reconfiguring. If you do need to reconfigure, take note of the following:
If configure is run after it has previously been run, it may use information that was gathered during its previous invocation. This information is stored in config.cache. When configure starts up, it looks for that file and reads its contents if it exists, on the assumption that the information is still correct. That assumption is invalid when you reconfigure.
Each time you run configure, you must run make again to recompile. However, you may want to remove old object files from previous builds first because they were compiled using different configuration options.
To prevent old configuration information or object files from being used, run these commands before re-running configure:
shell> rm config.cache
shell> make clean
Alternatively, you can run make distclean.
从源码configure,make编译成binary时
如果需要改变配置重新来一次，需要删除config.cache,及老的二进制对像文件

3, 对于myisam引擎的表,如果更改了表的字符集,需要用myisamchk修复表与索引数据，使一致!

If you change character sets after having created any tables, you must run myisamchk -r -q --set-collation=collation_name on every MyISAM table. Your indexes may be sorted incorrectly otherwise. This can happen if you install MySQL, create some tables, and then reconfigure MySQL to use a different character set and reinstall it.

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