DESCRIPTION

This documentation is about what special support Alzabo has for MySQL, as well as what is lacking.

MySQL support is based on the 3.23.* release series, with some support for features that are starting to appear in the 4.0.* releases. Earlier versions of MySQL will probably work with Alzabo, though Alzabo cannot magically make these releases support new features like fulltext indexes.

Indexes

• Alzabo supports the ability to specify prefixes when adding an index. Prefixes are required when attempting to index any sort of text or blob column.
• Alzabo supports the creation of fulltext indexes and their use in SELECT and WHERE clauses. This includes the ability to get back the score given for a match as part of a select, using the "function" or "select" methods of either table or schema objects.

Reverse Engineering

• When reverse engineering a schema, Alzabo knows that MySQL has ``default defaults'' for certain column types. For example, if a DATE column is specified as NOT NULL but is not assigned a default, MySQL gives this column a default of '0000-00-00'.

  Because Alzabo knows about this, it will ignore these defaults when reverse engineering an RDBMS.

• Similarly, Alzabo knows that MySQL assigns default ``lengths'' to many column types. For example, if given INTEGER as a column type, MySQL will convert this to INTEGER(11) or INTEGER(10), depending on the version of MySQL being used.

  Again, Alzabo ignores these lengths when reverse engineering a schema.

• All of this may lead to apparent inconsistencies when using the with the "Alzabo::Create::Schema->sync_backend" or "Alzabo::Create::Schema->sync_backend_sql" methods. If you are using this feature from the web based schema creator, you will see that even immediately after running the "sync_backend()" method, Alzabo may still think there are differences between the two schemas. This is not a problem, as running the SQL Alzabo generates will not actually change your database.

Transactions

Alzabo will try to use transactions whenever appropriate. Unfortunately, there is no way to determine whether or not a given table supports transactions so Alzabo simply calls DBI's "begin_work()" method, whether or not this will actually do anything.

Constraints and Foreign Keys

• Column constraints are treated as column attributes.
• Foreign key constraints are not generated when generating SQL for a MySQL schema. This will probably change in the future.

Table Types

These can be specified as a table attribute.