NAME

       Alzabo::RDBMSRules - 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, <dave@urth.org>