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спецификации, руководства, описания, API
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The information in this section applies to MySQL Cluster running on both Unix and Windows platforms.
Working with database tables and data in MySQL Cluster is not much different from doing so in standard MySQL. There are two key points to keep in mind:
For a table to be replicated in the cluster, it must use the NDBCLUSTER
storage engine. To specify this, use the ENGINE=NDBCLUSTER
or ENGINE=NDB
option when
creating the table:
CREATE TABLEtbl_name
(col_name
column_definitions
) ENGINE=NDBCLUSTER;
Alternatively, for an existing table that uses a different storage engine, use ALTER TABLE
to change the table to use NDBCLUSTER
:
ALTER TABLE tbl_name
ENGINE=NDBCLUSTER;
Every NDBCLUSTER
table has a primary key. If no primary key is defined by the
user when a table is created, the NDBCLUSTER
storage engine automatically generates a hidden one. Such a key takes up space just as does any other
table index. (It is not uncommon to encounter problems due to insufficient memory for accommodating
these automatically created indexes.)
If you are importing tables from an existing database using the output of mysqldump, you can open the SQL script in a text editor and add
the ENGINE
option to any table creation statements, or replace any existing ENGINE
options. Suppose that you have the world
sample database on another MySQL server that does not support MySQL Cluster, and you want to export the City
table:
shell> mysqldump --add-drop-table world City >
city_table.sql
The resulting city_table.sql
file will contain this table creation statement (and
the INSERT
statements necessary to import the table data):
DROP TABLE IF EXISTS `City`;CREATE TABLE `City` ( `ID` int(11) NOT NULL auto_increment, `Name` char(35) NOT NULL default '', `CountryCode` char(3) NOT NULL default '', `District` char(20) NOT NULL default '', `Population` int(11) NOT NULL default '0', PRIMARY KEY (`ID`)) ENGINE=MyISAM DEFAULT CHARSET=latin1;INSERT INTO `City` VALUES (1,'Kabul','AFG','Kabol',1780000);INSERT INTO `City` VALUES (2,'Qandahar','AFG','Qandahar',237500);INSERT INTO `City` VALUES (3,'Herat','AFG','Herat',186800);(remaining INSERT statements omitted)
You need to make sure that MySQL uses the NDBCLUSTER
storage engine for this table. There are two ways that this can be accomplished. One of these is to modify the
table definition before importing it into the Cluster database. Using the
City
table as an example, modify the ENGINE
option of
the definition as follows:
DROP TABLE IF EXISTS `City`;CREATE TABLE `City` ( `ID` int(11) NOT NULL auto_increment, `Name` char(35) NOT NULL default '', `CountryCode` char(3) NOT NULL default '', `District` char(20) NOT NULL default '', `Population` int(11) NOT NULL default '0', PRIMARY KEY (`ID`)) ENGINE=NDBCLUSTER DEFAULT CHARSET=latin1;INSERT INTO `City` VALUES (1,'Kabul','AFG','Kabol',1780000);INSERT INTO `City` VALUES (2,'Qandahar','AFG','Qandahar',237500);INSERT INTO `City` VALUES (3,'Herat','AFG','Herat',186800);(remaining INSERT statements omitted)
This must be done for the definition of each table that is to be part of the clustered database. The easiest way
to accomplish this is to do a search-and-replace on the file that contains the definitions and replace all
instances of TYPE=
or engine_name
ENGINE=
with engine_name
ENGINE=NDBCLUSTER
. If you do not want to modify the file, you can use the
unmodified file to create the tables, and then use ALTER
TABLE
to change their storage engine. The particulars are given later in this section.
Assuming that you have already created a database named world
on the SQL node of
the cluster, you can then use the mysql command-line client to read city_table.sql
,
and create and populate the corresponding table in the usual manner:
shell> mysql world <
city_table.sql
It is very important to keep in mind that the preceding command must be executed on the host where the SQL node
is running (in this case, on the machine with the IP address 192.168.0.20
).
To create a copy of the entire world
database on the SQL node, use mysqldump on the noncluster server to export the database to a
file named world.sql
; for example, in the /tmp
directory. Then modify the table definitions as just described and import the file into the SQL node of the
cluster like this:
shell> mysql world <
/tmp/world.sql
If you save the file to a different location, adjust the preceding instructions accordingly.
Running SELECT
queries on the SQL node is no different from running them on any other
instance of a MySQL server. To run queries from the command line, you first need to log in to the MySQL Monitor
in the usual way (specify the root
password at the Enter
password:
prompt):
shell> mysql -u root -p
Enter password:Welcome to the MySQL monitor. Commands end with ; or \g.Your MySQL connection id is 1 to server version: 5.6.11-ndb-7.3.3Type 'help;' or '\h' for help. Type '\c' to clear the buffer.mysql>
We simply use the MySQL server's root
account and assume that you have followed the
standard security precautions for installing a MySQL server, including setting a strong root
password. For more information, see Section 2.10.2,
"Securing the Initial MySQL Accounts".
It is worth taking into account that Cluster nodes do not make use of the
MySQL privilege system when accessing one another. Setting or changing MySQL user accounts (including the root
account) effects only applications that access the SQL node, not interaction
between nodes. See Section 17.5.11.2, "MySQL Cluster
and MySQL Privileges", for more information.
If you did not modify the ENGINE
clauses in the table definitions prior to
importing the SQL script, you should run the following statements at this point:
mysql>USE world;
mysql>ALTER TABLE City ENGINE=NDBCLUSTER;
mysql>ALTER TABLE Country ENGINE=NDBCLUSTER;
mysql>ALTER TABLE CountryLanguage ENGINE=NDBCLUSTER;
Selecting a database and running a SELECT query against a table in that database is also accomplished in the usual manner, as is exiting the MySQL Monitor:
mysql>USE world;
mysql>SELECT Name, Population FROM City ORDER BY Population DESC LIMIT 5;
+-----------+------------+| Name | Population |+-----------+------------+| Bombay | 10500000 || Seoul | 9981619 || São Paulo | 9968485 || Shanghai | 9696300 || Jakarta | 9604900 |+-----------+------------+5 rows in set (0.34 sec)mysql>\q
Byeshell>
Applications that use MySQL can employ standard APIs to access NDB
tables. It is important to remember that your application must access the SQL
node, and not the management or data nodes. This brief example shows how we might execute the SELECT
statement just shown by using the PHP 5.X mysqli
extension running on a Web server elsewhere on the network:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <title>SIMPLE mysqli SELECT</title></head><body><?php # connect to SQL node: $link = new mysqli('192.168.0.20', 'root', 'root_password
', 'world'); # parameters for mysqli constructor are: # host, user, password, database if( mysqli_connect_errno() ) die("Connect failed: " . mysqli_connect_error()); $query = "SELECT Name, Population FROM City ORDER BY Population DESC LIMIT 5"; # if no errors... if( $result = $link->query($query) ) {?><table border="1" width="40%" cellpadding="4" cellspacing ="1"> <tbody> <tr> <th width="10%">City</th> <th>Population</th> </tr><? # then display the results... while($row = $result->fetch_object()) printf("<tr>\n <td align=\"center\">%s</td><td>%d</td>\n</tr>\n", $row->Name, $row->Population);?> </tbody</table><? # ...and verify the number of rows that were retrieved printf("<p>Affected rows: %d</p>\n", $link->affected_rows); } else # otherwise, tell us what went wrong echo mysqli_error(); # free the result set and the mysqli connection object $result->close(); $link->close();?></body></html>
We assume that the process running on the Web server can reach the IP address of the SQL node.
In a similar fashion, you can use the MySQL C API, Perl-DBI, Python-mysql, or MySQL Connectors to perform the tasks of data definition and manipulation just as you would normally with MySQL.