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:
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 to get more speed. The current implementation limits
the number of open files that MySQL 5.1 can use
to 2,048, which means that you cannot run as many concurrent
threads on Windows 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.
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.
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 nonfunctional
realpath()
call.
You cannot drop a database that is in use by another thread.
Case-insensitive names
File names 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 Section 8.2.2, “Identifier Case Sensitivity”.
Directory and file names
On Windows, MySQL Server supports only directory and file names that are compatible with the current ANSI code pages. For example, the following Japanese directory name will not work in the Western locale (code page 1252):
datadir="C:/私たちのプロジェクトのデータ"
The same limitation applies to directory and file names
referred to in SQL statements, such as the data file path name
in LOAD DATA
INFILE
.
The “\
”
path name separator character
Path name 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 file names 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
C:\>binary_log_file
--result-file=/tmp/bin.sqlmysql --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 host name 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.
User Comments
Quote: "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."
Windows does allow files to be deleted while still in use if all currently open handles are opened with FILE_SHARE_DELETE.
There is usually no reason to omit this flag when opening a file. If your code relies on the Unix behavior, which appears to be similar to always specifying FILE_SHARE_DELETE, then just change all your CreateFile() calls to use this flag, and you will get the desired behavior.
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