(mysql.info) windows-vs-unix
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(mysql.info) windows-upgrading
(mysql.info) windows-installation
2.3.15 MySQL on Windows Compared to MySQL on Unix
-------------------------------------------------
MySQL for Windows has proven itself to be very stable. The Windows
version of MySQL has the same features as the corresponding Unix
version, with the following exceptions:
* *Windows 95 and threads*
Windows 95 leaks about 200 bytes of main memory for each thread
creation. Each connection in MySQL creates a new thread, so you
shouldn't run `mysqld' for an extended time on Windows 95 if your
server handles many connections! Newer versions of Windows don't
suffer from this bug.
* *Limited number of ports*
Windows systems have about 4,000 ports available for client
connections, and after a connection on a port closes, it takes two
to four minutes before the port can be reused. In situations where
clients connect to and disconnect from the server at a high rate,
it is possible for all available ports to be used up before closed
ports become available again. If this happens, the MySQL server
appears to be unresponsive even though it is running. Note that
ports may be used by other applications running on the machine as
well, in which case the number of ports available to MySQL is
lower.
For more information about this problem, see
`http://support.microsoft.com/default.aspx?scid=kb;en-us;196271'.
* *Concurrent reads*
MySQL depends on the `pread()' and `pwrite()' system calls to be
able to mix `INSERT' and `SELECT'. Currently, we use mutexes to
emulate `pread()' and `pwrite()'. We intend to replace the file
level interface with a virtual interface in the future so that we
can use the `readfile()'/`writefile()' interface on NT, 2000, and
XP to get more speed. The current implementation limits the number
of open files that MySQL 5.0 can use to 2,048, which means that you
cannot run as many concurrent threads on Windows NT, 2000, XP, and
2003 as on Unix.
* *Blocking read*
MySQL uses a blocking read for each connection. That has the
following implications if named-pipe connections are enabled:
* A connection is not disconnected automatically after eight
hours, as happens with the Unix version of MySQL.
* If a connection hangs, it is not possible to break it without
killing MySQL.
* `mysqladmin kill' does not work on a sleeping connection.
* `mysqladmin shutdown' cannot abort as long as there are
sleeping connections.
We plan to fix this problem in the future.
* *`ALTER TABLE'*
While you are executing an `ALTER TABLE' statement, the table is
locked from being used by other threads. This has to do with the
fact that on Windows, you can't delete a file that is in use by
another thread. In the future, we may find some way to work around
this problem.
* *`DROP TABLE'*
`DROP TABLE' on a table that is in use by a `MERGE' table does not
work on Windows because the `MERGE' handler does the table mapping
hidden from the upper layer of MySQL. Because Windows does not
allow dropping files that are open, you first must flush all
`MERGE' tables (with `FLUSH TABLES') or drop the `MERGE' table
before dropping the table.
* *`DATA DIRECTORY' and `INDEX DIRECTORY'*
The `DATA DIRECTORY' and `INDEX DIRECTORY' options for `CREATE
TABLE' are ignored on Windows, because Windows doesn't support
symbolic links. These options also are ignored on systems that
have a non-functional `realpath()' call.
* *`DROP DATABASE'*
You cannot drop a database that is in use by some thread.
* *Killing MySQL from the Task Manager*
On Windows 95, you cannot kill MySQL from the Task Manager or with
the shutdown utility. You must stop it with `mysqladmin shutdown'.
* *Case-insensitive names*
Filenames are not case sensitive on Windows, so MySQL database and
table names are also not case sensitive on Windows. The only
restriction is that database and table names must be specified
using the same case throughout a given statement. See
name-case-sensitivity.
* *The ‘`\'’ pathname separator character*
Pathname components in Windows are separated by the ‘`\'’
character, which is also the escape character in MySQL. If you are
using `LOAD DATA INFILE' or `SELECT ... INTO OUTFILE', use
Unix-style filenames with ‘`/'’ characters:
mysql> LOAD DATA INFILE 'C:/tmp/skr.txt' INTO TABLE skr;
mysql> SELECT * INTO OUTFILE 'C:/tmp/skr.txt' FROM skr;
Alternatively, you must double the ‘`\'’ character:
mysql> LOAD DATA INFILE 'C:\\tmp\\skr.txt' INTO TABLE skr;
mysql> SELECT * INTO OUTFILE 'C:\\tmp\\skr.txt' FROM skr;
* *Problems with pipes*
Pipes do not work reliably from the Windows command-line prompt.
If the pipe includes the character `^Z' / `CHAR(24)', Windows
thinks that it has encountered end-of-file and aborts the program.
This is mainly a problem when you try to apply a binary log as
follows:
C:\> mysqlbinlog BINARY_LOG_FILE | mysql --user=root
If you have a problem applying the log and suspect that it is
because of a `^Z' / `CHAR(24)' character, you can use the
following workaround:
C:\> mysqlbinlog BINARY_LOG_FILE --result-file=/tmp/bin.sql
C:\> mysql --user=root --execute "source /tmp/bin.sql"
The latter command also can be used to reliably read in any SQL
file that may contain binary data.
* *`Access denied for user' error*
If MySQL cannot resolve your hostname properly, you may get the
following error when you attempt to run a MySQL client program to
connect to a server running on the same machine:
Access denied for user 'SOME_USER'@'unknown'
to database 'mysql'
To fix this problem, you should create a file named
`\windows\hosts' containing the following information:
127.0.0.1 localhost
Here are some open issues for anyone who might want to help us improve
MySQL on Windows:
* Add macros to use the faster thread-safe increment/decrement
methods provided by Windows.
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