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(Continued from previous question...)
MySQL - Using Symbolic Links for Databases and Tables
You can move tables and databases from the database directory to other locations and replace them with symbolic links to the
new locations. You might want to do this, for example, to move a database to a file system with more free space.
If MySQL notices that a table is symbolically linked, it will resolve the symlink and use the table it points to instead.
This works on all systems that support the realpath() call (at least Linux and Solaris support realpath())! On systems that
don't support realpath(), you should not access the table through the real path and through the symlink at the same time! If
you do, the table will be inconsistent after any update.
MySQL doesn't that you link one directory to multiple databases. Replacing a database directory with a symbolic link will
work fine as long as you don't make a symbolic link between databases. Suppose you have a database db1 under the MySQL data
directory, and then make a symlink db2 that points to db1:
shell> cd /path/to/datadir
shell> ln -s db1 db2
Now, for any table tbl_a in db1, there also appears to be a table tbl_a in db2. If one thread updates db1.tbl_a and another
thread updates db2.tbl_a, there will be problems.
If you really need this, you must change the following code in `mysys/mf_format.c':
if (flag & 32 || (!lstat(to,&stat_buff) && S_ISLNK(stat_buff.st_mode)))
to
if (1)
On Windows you can use internal symbolic links to directories by compiling MySQL with -DUSE_SYMDIR. This allows you to put
different databases on different disks.
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