Alzabo::RDBMSRules(3) Base class for Alzabo RDBMS rulesets

SYNOPSIS


use Alzabo::RDBMSRules;
my $rules = Alzabo::RDBMSRules( rules => 'MySQL' );

DESCRIPTION

This class is the base class for all "Alzabo::RDBMSRules" modules. To instantiate a subclass call this class's "new()" method. See the ``SUBCLASSING Alzabo::RDBMSRules'' section for information on how to make a ruleset for the RDBMS of your choice.

METHODS

available

A list of names representing the available "Alzabo::RDBMSRules" subclasses. Any one of these names would be appropriate as the ``rdbms'' parameter for the "Alzabo::RDBMSRules->new()" method.

new

The constructor always accepts one parameter, ``rdbms'', which is the name of the RDBMS to be used.

Some subclasses may accept additional values.

The constructor returns a new "Alzabo::RDBMSRules" object of the appropriate subclass.

Throws: "Alzabo::Exception::Eval"

schema_sql (Alzabo::Create::Schema object)

Returns a list of SQL statements which would create the given schema.

index_sql (Alzabo::Create::Index object)

Returns a list of SQL statements to create the specified index.

drop_table_sql (Alzabo::Create::Table object)

Returns a list of SQL statements to drop the specified table.

drop_index_sql (Alzabo::Create::Index object)

Returns a list of SQL statements to drop the specified index.

schema_sql_diff

This method takes two parameters:
  • new => "Alzabo::Create::Schema" object
  • old => "Alzabo::Create::Schema" object

This method compares the two schema objects and returns an array of SQL statements which turn the ``old'' schema into the ``new'' one.

table_sql_diff

This method takes two parameters:
  • new => "Alzabo::Create::Table" object
  • old => "Alzabo::Create::Table" object

This method compares the two table objects and returns an array of SQL statements which turn the ``old'' table into the ``new'' one.

type_is_numeric (Alzabo::Column object)

Returns a boolean indicating whether or not the column is numeric (integer or floating point).

quote_identifiers

Returns true or false to indicate whether or not the generated DDL SQL statements should have their identifiers quoted or not. This may be overridden by subclasses. It defaults to false.

can_alter_table_name

If this is true, then when syncing a schema, the object will call "alter_table_name_sql()" to change the table's name. Otherwise it will call "recreate_table_sql()".

can_alter_column_name

If this is true, then when syncing a schema, the object will call "alter_column_name_sql()" to change the table's name. Otherwise it will call "recreate_table_sql()".

Virtual Methods

The following methods are not implemented in the "Alzabo::RDBMSRules" class itself and must be implemented in its subclasses.

column_types

Returns a list of valid column types.

feature ($feature)

Given a string defining a feature, this method indicates whether or not the given RDBMS supports that feature. By default, this method always returns false unless overridden in the subclass.

Features that may be asked for:

  • extended_column_types

    Column types that must be input directly from a user, as opposed to being chosen from a list. MySQL's ENUM and SET types are examples of such types.

  • index_column_prefixes

    MySQL supports the notion of column prefixes in indexes, allowing you to index only a portion of a large text column.

  • fulltext_indexes

    This should be self-explanatory.

  • functional_indexes

    Indexes on functions, as supported by PostgreSQL.

validate_schema_name (Alzabo::Schema object)

Throws an "Alzabo::Exception::RDBMSRules" if the schema's name is not valid.

validate_table_name (Alzabo::Create::Table object)

Throws an "Alzabo::Exception::RDBMSRules" if the table's name is not valid.

validate_column_name (Alzabo::Create::Column object)

Throws an "Alzabo::Exception::RDBMSRules" if the column's name is not valid.

validate_column_type ($type_as_string)

Throws an "Alzabo::Exception::RDBMSRules" if the type is not valid.

This method returns a canonized version of the type.

validate_column_length (Alzabo::Create::Column object)

Throws an "Alzabo::Exception::RDBMSRules" if the length or precision is not valid for the given column.

validate_column_attribute

This method takes two parameters:
  • column => "Alzabo::Create::Column" object
  • attribute => $attribute

This method is a bit different from the others in that it takes an existing column object and a potential attribute.

It throws an "Alzabo::Exception::RDBMSRules" if the attribute is is not valid for the column.

validate_primary_key (Alzabo::Create::Column object)

Throws an "Alzabo::Exception::RDBMSRules" if the column is not a valid primary key for its table.

validate_sequenced_attribute (Alzabo::Create::Column object)

Throws an "Alzabo::Exception::RDBMSRules" if the column cannot be sequenced.

validate_index (Alzabo::Create::Index object)

Throws an "Alzabo::Exception::RDBMSRules" if the index is not valid.

table_sql (Alzabo::Create::Table object)

Returns an array of SQL statements to create the specified table.

column_sql (Alzabo::Create::Column object)

Returns an array of SQL statements to create the specified column.

foreign_key_sql (Alzabo::Create::ForeignKey object)

Returns an array of SQL statements to create the specified foreign key.

drop_column_sql (Alzabo::Create::Column object)

Returns an array of SQL statements to drop the specified column.

drop_foreign_key_sql (Alzabo::Create::ForeignKey object)

Returns an array of SQL statements to drop the specified foreign key.

column_sql_add (Alzabo::Create::Column object)

Returns an array of SQL statements to add the specified column.

column_sql_diff

This method takes two parameters:
  • new => "Alzabo::Create::Column" object
  • old => "Alzabo::Create::Column" object

This method compares the two table objects and returns an array of SQL statements which turn the ``old'' table into the ``new'' one.

index_sql_diff

This method takes two parameters:
  • new => "Alzabo::Create::Index" object
  • old => "Alzabo::Create::Index" object

This method compares the two index objects and returns an array of SQL statements which turn the ``old'' index into the ``new'' one.

alter_primary_key_sql

This method takes two parameters:
  • new => "Alzabo::Create::Table" object
  • old => "Alzabo::Create::Table" object

This method compares the two table objects and returns an array of SQL statements which alter the ``old'' one's primary key to match the ``new'' one's.

alter_table_name_sql (Alzabo::Create::Table object)

Given a table, this method is expected to change the table's name from "$table->former_name" to "$table->name". This will only be called if the rules object returns true for "can_alter_table_name()".

alter_column_name_sql (Alzabo::Create::Table object)

Given a column, this method is expected to change the table's name from "$column->former_name" to "$column->name". This will only be called if the rules object returns true for "can_alter_column_name()".

recreate_table_sql

This method takes two parameters:
  • new => "Alzabo::Create::Table" object
  • old => "Alzabo::Create::Table" object

This method is expected to drop the old table and create the new one.

However, it must preserve all the data stored in the old table, excluding data in columns that are being dropped. Additionally, if there are sequences associated with columns in the old table, they should not be dropped.

This method will only be called if either "can_alter_table_name()" or "can_alter_column_name()" return false.

reverse_engineer (Alzabo::Create::Schema object)

Given a schema object (which presumably has no tables), this method uses the schema's "Alzabo::Driver" object to connect to an existing database and reverse engineer it into the appropriate Alzabo objects.

type_is_integer (Alzabo::Column object)

Returns a boolean indicating whether or not the column is an integer type.

type_is_floating_point (Alzabo::Column object)

Returns a boolean indicating whether or not the column is a floating point type.

type_is_character (Alzabo::Column object)

Returns a boolean indicating whether or not the column is a character type. This is defined as any type which is defined to store text, regardless of length.

type_is_date (Alzabo::Column object)

Returns a boolean indicating whether or not the column is a date type. This is not true for datetime types.

type_is_datetime (Alzabo::Column object)

Returns a boolean indicating whether or not the column is a datetime type. This is not true for date types.

type_is_time (Alzabo::Column object)

Returns a boolean indicating whether or not the column is a time type. This is not true for datetime types.

type_is_time_interval (Alzabo::Column object)

Returns a boolean indicating whether or not the column is a time interval type.

SUBCLASSING Alzabo::RDBMSRules

To create a subclass of "Alzabo::RDBMSRules" for your particular RDBMS is fairly simple.

Here's a sample header to the module using a fictional RDBMS called FooDB: 

 package Alzabo::RDBMSRules::FooDB;
 use strict;
 use vars qw($VERSION);
 use Alzabo::RDBMSRules;
 use base qw(Alzabo::RDBMSRules);

The next step is to implement a "new()" method and the methods listed under the section ``Virtual Methods''. The new method should look a bit like this: 

 1:  sub new
 2:  {
 3:      my $proto = shift;
 4:      my $class = ref $proto || $proto;
 5:      my %p = @_;
 6:
 7:      my $self = bless {}, $self;
 8:
 9:      return $self;
 10:  }

The hash %p contains any values passed to the "Alzabo::RDBMSRules->new" method by its caller.

Lines 1-7 should probably be copied verbatim into your own "new" method. Line 5 can be deleted if you don't need to look at the parameters.

The rest of your module should simply implement the methods listed under the ``Virtual Methods'' section of this documentation.

Look at the included "Alzabo::RDBMSRules" subclasses for examples. Feel free to contact me for further help if you get stuck. Please tell me what database you're attempting to implement, and include the code you've written so far.

AUTHOR

Dave Rolsky, <[email protected]>

LAST SEARCHED