bk commit - mysqldoc tree (1.958)

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ChangeSet
  1.958 03/10/28 12:30:09 guilhem@xxxxxxxxx +1 -0
  Adding a warning "you should not symlink the FRM file".
  Thread (october 2003)
  "RE: reproducible error 17
  on the mysql lists led to this.

  Docs/manual.texi
    1.873 03/10/28 12:30:05 guilhem@xxxxxxxxx +23 -1
    Adding a warning "you should not symlink the FRM file".

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User: guilhem
# Host: gbichot2
# Root: /home/mysql_src/mysqldoc

--- 1.872/Docs/manual.texi      Mon Oct 27 20:28:00 2003
+++ 1.873/Docs/manual.texi      Tue Oct 28 12:30:05 2003
@@ -33179,7 +33179,29 @@
 @item
 @code{mysqldump} doesn't include the symbolic link information in the output.
 @item
-@code{BACKUP TABLE} and @code{RESTORE TABLE} don't respect symbolic links.
+@code{BACKUP TABLE} and @code{RESTORE TABLE} don't respect symbolic
+links.
+@item
+The @code{frm} file must @strong{never} be a symbolic link (as said
+previously, only the data and index files can be symbolic links).
+Doing this (for example to make synonyms), will produce wrong
+results.
+Suppose you have a database @code{db1} under the MySQL data
+directory, a table @code{tbl1} in this database, and in the @code{db1}
+directory you make a symlink @code{tbl2} that points to @code{tbl1}:
+
+@example
+shell> cd /path/to/datadir/db1
+shell> ln -s tbl1.frm tbl2.frm
+shell> ln -s tbl1.MYD tbl2.MYD
+shell> ln -s tbl1.MYI tbl2.MYI
+@end example
+
+Now if one thread reads @code{db1.tbl1} and another thread updates
+@code{db1.tbl2}, there will be problems: the query cache will be fooled
+(it will believe @code{tbl1} has not been updated so will return
+out-of-date results), the @code{ALTER} commands on @code{tbl2} will also
+fail.
 @end itemize
 
 

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