NAME

DBIx::SQLEngine::Driver::Trait::DatabaseFlavors - For minor variations in a database

SYNOPSIS

  # Classes can import this behavior if they have further subclasses
  use DBIx::SQLEngine::Driver::Trait::DatabaseFlavors ':all';

DESCRIPTION

This package supports configurations of drivers or database servers which differ from the generic implementation provided by their driver.

Variations Within a Driver Class

Beyond the fundamental subclassing based on driver type lies a more subtle range of variations.

How do we compensate for different versions of a database system? For example, newer versions of MySQL support a number of features that the old ones don't: transactions were added in 3.23 (for some table types); union selects were added in 4.0; and stored procedures are being added in 5.0. Similarly DBD::SQLite's functionality is limited by the version of the SQLite C library is in use, and DBD::AnyData's level of functionality depends on which version of SQL::Statement is installed.

Similarly, how do we detect driver/server combinations that need extra help? For example, placeholders will fail for Linux users of DBD::Sybase connecting to MS SQL Servers on Windows, so they need a special subclass which uses the NoPlaceholders trait.

This is handled by the "dbms_flavor" interface. When a flavor is selected, detected, or defaulted, the driver in question is reblessed into an appropriate subclass, such as Driver::MySQL::3_23, Driver::MySQL::5_0, or Driver::Sybase::MSSQL.

About Driver Traits

You do not need to use this package directly; it is used internally by those driver subclasses which need it.

For more information about Driver Traits, see "About Driver Traits" in DBIx::SQLEngine::Driver.

INTERNAL CONNECTION METHODS (DBI DBH)

Initialization and Reconnection

_init()

  $sqldb->_init ()

Calls select_default_dbms_flavor().

Internal method, called by DBIx::AnyDBD after connection is made and class hierarchy has been juggled.

DRIVER AND DATABASE FLAVORS

Detecting DBMS Flavors

default_dbms_flavor()

  $sqldb->default_dbms_flavor() : $flavor_name

Subclass hook. Default returns empty string, to not select any flavor.

detect_dbms_flavor()

  $sqldb->detect_dbms_flavor() : $flavor_name

Subclass hook. Default returns empty string, to not select any flavor.

Applying DBMS Flavors

select_dbms_flavor()

  $sqldb->select_dbms_flavor( $flavor_name )

Reblesses the driver to a subclass based on the flavor name.

select_default_dbms_flavor()

  $sqldb->select_default_dbms_flavor( )

Calls select_dbms_flavor() with the result of default_dbms_flavor().

select_detect_dbms_flavor()

  $sqldb->select_detect_dbms_flavor( )

Calls select_dbms_flavor() with the result of detect_dbms_flavor() or default_dbms_flavor().