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Alzabo::Driver - Alzabo base class for RDBMS drivers |
Alzabo::Column object)
Alzabo::Driver - Alzabo base class for RDBMS drivers
use Alzabo::Driver;
my $driver = Alzabo::Driver->new( rdbms => 'MySQL',
schema => $schema );
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.
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.
Alzabo::Schema object
A new Alzabo::Driver object of the appropriate subclass.
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.
This method takes one optional parameter, a connected DBI handle. If this is given, then this handle is the new handle for the driver.
The active database handle.
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.
$offset defaults to 0.
This parameters 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.
An array of array references containing the data requested.
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.
An array or scalar containing the data returned, depending on context.
A hash containing the data requested. The hash keys are the columns being selected. All the key names are in uppercase.
An array containing the values for the first column of each row returned.
Use this for non-SELECT SQL statements.
The number of rows affected.
$offset defaults to 0.
A new Alzabo::DriverStatement handle,
ready to return data via the
Alzabo::DriverStatement->next_row
or
Alzabo::DriverStatement->next_row_hash
methods.
This class is a wrapper around DBI's statement handles. It finishes
automatically as appropriate so the end user does need not worry about
doing this.
Use this method in a while loop to fetch all the data from a statement.
An array containing the next row of data for statement or an empty list if no more data is available.
A hash containing the next row of data for statement or an empty list if no more data is available. All the keys of the hash are in uppercase.
Executes the associated statement handle with the given bound
parameters. If the statement handle is still active (it was
previously executed and has more data left) then its finish method
will be called first.
In addition to the methods inherited from
Exception::Class::Base, objects in this
class also contain several methods specific to this subclass.
The SQL statement in use at the time the error occurred, if any.
A list of the the bound parameters for the SQL statement, if any.
To create a subclass of Alzabo::Driver for your particular RDBMS is
fairly simple. First of all, there must be a DBD::* driver for it,
as Alzabo::Driver is built on top of DBI.
Here's a sample header to the module using a fictional RDBMS called FooDB:
package Alzabo::Driver::FooDB;
use strict; use vars qw($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.
The following methods are not implemented in Alzabo::Driver itself
and must be implemented in a subclass.
All of these default to undef. See the appropriate DBD driver documentation for more details.
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.
Attempts to create a new database for the schema attached to the driver. Some drivers may accept or require more arguments than specified above.
Attempts to drop the database for the schema attached to the driver.
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
Alzabo code that calls this method.
Notify Alzabo that you wish to start a transaction.
Not yet determined.
Rolls back the current transaction.
Notify Alzabo that you wish to finish a transaction. This is basically the equivalent of calling commit.
Not yet determined.
The last primary key id created via a sequenced column.
Dave Rolsky, <dave@urth.org>
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Alzabo::Driver - Alzabo base class for RDBMS drivers |