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Platforms
Platforms abstract query generation and the subtle differences of
the supported database vendors. In most cases you don't need to
interact with the Doctrine\DBAL\Platforms
package a lot, but
there might be certain cases when you are programming database
independent where you want to access the platform to generate
queries for you.
The platform can be accessed from any Doctrine\DBAL\Connection
instance by calling the getDatabasePlatform()
method.
Each database driver has a platform associated with it by default.
Several drivers also share the same platform, for example PDO_OCI
and OCI8
share the OraclePlatform
.
Doctrine provides abstraction for different versions of platforms if necessary to represent their specific features and dialects. For example has Microsoft added support for sequences in their 2012 version. Therefore Doctrine offers a separate platform class for this extending the previous 2008 version. The 2008 version adds support for additional data types which in turn don't exist in the previous 2005 version and so on. A list of available platform classes that can be used for each vendor can be found as follows:
MySQL
MySQLPlatform
for version 8.0 and above.MySQL84Platform
for version 8.4 and above.
MariaDB
MariaDBPlatform
for version 10.5.2 and above.MariaDb1060Platform
for version 10.6 and above.MariaDB1010Platform
for version 10.10 and above.
Oracle
OraclePlatform
for version 18c (12.2.0.2) and above.
Microsoft SQL Server
SQLServerPlatform
for version 2017 and above.
PostgreSQL
PostgreSQLPlatform
for version 12.0 and above.
IBM DB2
Db2Platform
for all versions.
SQLite
SQLitePlatform
for all versions.
It is highly encouraged to use the platform class that matches your database vendor and version best. Otherwise it is not guaranteed that the compatibility in terms of SQL dialect and feature support between Doctrine DBAL and the database server will always be given.
If you want to overwrite parts of your platform you can do so by using a middleware:
1 <?php
class CustomSQLitePlatform extends SqlitePlatform {}
class CustomDriver extends AbstractDriverMiddleware
{
public function getDatabasePlatform(ServerVersionProvider $versionProvider)
{
return new CustomSQLitePlatform();
}
}
class CustomMiddleware implements Driver\Middleware
{
public function wrap(Driver $driver): Driver
{
return new CustomDriver($driver);
}
}
$config = new Doctrine\DBAL\Configuration();
$config->setMiddlewares([new CustomMiddleware()]);
$connection = DriverManager::getConnection($params, $config);
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This way you can optimize your schema or generated SQL code with features that might not be portable for instance, however are required for your special needs. This can include using triggers or views to simulate features or adding behaviour to existing SQL functions.
Platforms are also responsible to know which database type translates to which PHP Type. This is a very tricky issue across all the different database vendors, for example MySQL BIGINT and Oracle NUMBER should be handled as integer. Doctrine DBAL offers a powerful way to abstract the database to php and back conversion, which is described in the next section.