Provided by: libalzabo-perl_0.92-4_all bug

NAME

       Alzabo::Driver - Alzabo base class for RDBMS drivers

SYNOPSIS

         use Alzabo::Driver;

         my $driver = Alzabo::Driver->new( rdbms => 'MySQL',
                                           schema => $schema );

DESCRIPTION

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

       This class throws several, exceptions, one of which, "Alzabo::Exception::Driver", has
       additional methods not present in other exception classes.  See "Alzabo::Exception::Driver
       METHODS" for a description of these methods.

METHODS

   available
       Returns a list of names representing the available "Alzabo::Driver" subclasses.  Any one
       of these names would be appropriate as the "rdbms" parameter for the "Alzabo::Driver->new"
       method.

   new
       The constructor takes the following parameters:

       ·   rdbms => $rdbms_name

           The name of the RDBMS being used.

       ·   schema => "Alzabo::Schema" object

       It returns a new "Alzabo::Driver" object of the appropriate subclass.

       Throws: "Alzabo::Exception::Eval"

   tables
       Returns a list of strings containing the names of the tables in the database.  See the
       "DBI" documentation of the "DBI->tables" method for more details.

       Throws: "Alzabo::Exception::Driver"

   handle ($optional_dbh)
       This method takes one optional parameter, a connected DBI handle.  If this is given, then
       this handle is the new handle for the driver.

       It returns the active database handle.

       Throws: "Alzabo::Exception::Params"

   Data Retrieval methods
       Some of these methods return lists of data (the "rows", "rows_hashref", and "column"
       methods).  With large result sets, this can use a lot memory as these lists are created in
       memory before being returned to the caller.  To avoid this, it may be desirable to use the
       functionality provided by the "Alzabo::DriverStatement" class, which allows you to fetch
       results one row at a time.

       These methods all accept the following parameters:

       ·   sql => $sql_string

       ·   bind => $bind_value or \@bind_values

       ·   limit => [ $max, optional $offset ] (optional)

           The $offset defaults to 0.

           This parameter has no effect for the methods that return only one row.  For the
           others, it causes the drivers to skip $offset rows and then return only $max rows.
           This is useful if the RDBMS being used does not support "LIMIT" clauses.

   rows
       Returns an array of array references containing the data requested.

   rows_hashref
       Returns an array of hash references containing the data requested.  The hash reference
       keys are the columns being selected.  All the key names are in uppercase.

   one_row
       Returns an array or scalar containing the data returned, depending on context.

   one_row_hash
       Returns a hash containing the data requested.  The hash keys are the columns being
       selected.  All the key names are in uppercase.

   column
       Returns an array containing the values for the first column of each row returned.

   do
       Use this for non-SELECT SQL statements.

       Returns the number of rows affected.

       Throws: "Alzabo::Exception::Driver"

   statement
       This methods returns a new "Alzabo::DriverStatement" handle, ready to return data via the
       "Alzabo::DriverStatement->next()" or "Alzabo::DriverStatement->next_as_hash()" methods.

       Throws: "Alzabo::Exception::Driver"

   rdbms_version
       Returns the version string of the database backend currently in use.  The form of this
       string will vary depending on which driver subclass is being used.

   quote (@strings)
       This methods calls the underlying DBI handles "quote()" method on the array of strings
       provided, and returns the quoted versions.

   quote_identifier (@strings)
       This methods calls the underlying DBI handles "quote_identifier()" method on the array of
       strings provided, and returns the quoted versions.

Alzabo::DriverStatement

       This class is a wrapper around "DBI"'s statement handles.  It finishes automatically as
       appropriate so the end user does need not worry about doing this.

   next
       Use this method in a while loop to fetch all the data from a statement.

       Returns an array containing the next row of data for statement or an empty list if no more
       data is available.

       Throws: "Alzabo::Exception::Driver"

   next_as_hash
       For backwards compatibility, this is also available as "next_hash()".

       Returns a hash containing the next row of data for statement or an empty list if no more
       data is available.  All the keys of the hash will be lowercased.

       Throws: "Alzabo::Exception::Driver"

   all_rows
       If the select for which this statement is cursor was for a single column (or aggregate
       value), then this method returns an array containing each remaining value from the
       database.

       Otherwise, it returns an array of array references, each one containing a returned row
       from the database.

       Throws: "Alzabo::Exception::Driver"

   all_rows_hash
       Returns an array of hashes, each hash representing a single row returned from the
       database.  The hash keys are all in lowercase.

       Throws: "Alzabo::Exception::Driver"

   execute (@bind_values)
       Executes the associated statement handle with the given bound parameters.  If the
       statement handle is still active (it was previously executed and has more data left) then
       its "finish()" method will be called first.

       Throws: "Alzabo::Exception::Driver"

   count
       Returns the number of rows returned so far.

Alzabo::Exception::Driver METHODS

       In addition to the methods inherited from "Exception::Class::Base", objects in this class
       also contain several methods specific to this subclass.

   sql
       Returns the SQL statement in use at the time the error occurred, if any.

   bind
       Returns an array reference contaning the bound parameters for the SQL statement, if any.

SUBCLASSING Alzabo::Driver

       To create a subclass of "Alzabo::Driver" for your particular RDBMS is fairly simple.
       First of all, there must be a "DBD::*" driver for it, as "Alzabo::Driver" is built on top
       of "DBI".

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

        package Alzabo::Driver::FooDB;

        use strict;
        use vars qw($VERSION);

        use Alzabo::Driver;

        use DBI;
        use DBD::FooDB;

        use base qw(Alzabo::Driver);

       The next step is to implement a "new" method and the methods listed under "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 {}, $class;
        8:
        9:      return $self;
        10:  }

       The hash %p contains any values passed to the "Alzabo::Driver->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.

       Look at the included "Alzabo::Driver" 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, what its DBD::* driver is, and include the code you've written so far.

   Virtual Methods
       The following methods are not implemented in "Alzabo::Driver" itself and must be
       implemented in a subclass.

       Parameters for connect(), create_database(), and drop_database()

       ·   user => $db_username

       ·   password => $db_pw

       ·   host => $hostname

       ·   port => $port

       All of these default to undef.  See the appropriate DBD driver documentation for more
       details.

       After the driver is created, it will have access to its associated schema object in
       "$self->{schema}".

   connect
       Some drivers may accept or require more arguments than specified above.

       Note that "Alzabo::Driver" subclasses are not expected to cache connections.  If you want
       to do this please use "Apache::DBI" under mod_perl or don't call "connect()" more than
       once per process.

   create_database
       Attempts to create a new database for the schema attached to the driver.  Some drivers may
       accept or require more arguments than specified above.

   drop_database
       Attempts to drop the database for the schema attached to the driver.

   schemas
       Returns a list of schemas in the specified RDBMS.  This method may accept some or all of
       the parameters which can be given to "connect()".

   supports_referential_integrity
       Should return a boolean value indicating whether or not the RDBMS supports referential
       integrity constraints.

   next_sequence_number ("Alzabo::Column" object)
       This method is expected to return the value of the next sequence number based on a column
       object.  For some databases (MySQL, for example), the appropriate value is "undef".  This
       is accounted for in the Alzabo code that calls this method.

   begin_work
       Notify Alzabo that you wish to start a transaction.

   rollback
       Rolls back the current transaction.

   commit
       Notify Alzabo that you wish to finish a transaction.  This is basically the equivalent of
       calling commit.

   get_last_id
       Returns the last primary key id created via a sequenced column.

   rdbms_version
       Returns the version of the server to which the driver is connected.

   driver_id
       Returns the driver's name.  This should be something that can be passed to
       "Alzabo::Driver->new()" as a "name" parameter.

AUTHOR

       Dave Rolsky, <dave@urth.org>