Padre::DB(3) User Contributed Perl Documentation Padre::DB(3)NAMEPadre::DB - An ORLite-based ORM Database API
SYNOPSIS
TO BE COMPLETED
DESCRIPTION
This module implements access to the database that Padre is using to
store bits & pieces. It is using "ORLite" underneath, for an easy table
scheme discovery at runtime. See below to learn about how to update the
database scheme.
Updating database scheme
The database is created at runtime if it does not exist, but we are
relying on "Padre::DB::Migrate". To summarize "Padre::DB::Migrate":
· We provide scripts to update the database from one revision to
another.
· "Padre::DB" calls "Padre::DB::Migrate" to apply them in order,
starting from the current database revision.
Therefore, in order to update the database, you need to do the
following:
· Create a script share/timeline/migrate-$i.pl with $i the next
available integer. This script will look like this:
use strict;
use Padre::DB::Migrate::Patch;
# do some stuff on the base
do(<<'END_SQL');
<insert your sql statement here>
END_SQL
Of course, in case of dropping an existing table, you should make
sure that you don't loose data - that is, your script should
migrate existing data to the new scheme (unless the whole feature
is deprecated, of course).
· Update the user_revision in "Padre::DB"'s call to
"Padre::DB::Migrate" to read the new script number (i.e., the $i
that you have used to name your script in the timeline directory).
use Padre::DB::Migrate 0.01 {
[...]
user_revision => <your-revision-number>,
[...]
};
· Once this is done, you can try to load Padre's development and
check whether the table is updated correctly. Once again, check
whether data is correctly migrated from old scheme to new scheme
(if applicable).
Note that "Padre::DB::Migrate" is quiet by default. And if your SQL
statements are buggy, you will not see anything but the database
not being updated. Therefore, to debug what's going on, add the
"-DEBUG" flag to "Padre::DB::Migrate" call (add it as the last
parameter):
use Padre::DB::Migrate 0.01 {
[...]
}, '-DEBUG'
Congratulations! The database has been updated, and will be updated
automatically when users will run the new Padre version...
Accessing and using the database
Now that the database has been updated, you can start using it. Each
new table will have a "Padre::DB::YourTable" module created
automatically at runtime by "ORLite", providing you with the standard
methods described below (see METHODS).
Note: we prefer using underscore for table names instead of camel case.
"ORLite" is smart enough to convert underscore names to camel case
module names.
But what if you want to provide some particular methods? For example,
one can imagine that if you create a table "accessed_files" retaining
the path and the opening timestamp, you want to create a method
"most_recent()" that will return the last opened file.
In that case, that's quite easy, too:
· Create a standard "Padre::DB::YourTable" module where you will put
your method. Note that all standard methods described above will
still be available.
· Don't forget to "use Padre::DB::YourTable" in "Padre::DB", so that
other Padre modules will get access to all db tables by just using
"Padre::DB".
METHODS
Those methods are automatically created for each of the tables (see
above). Note that the modules automatically created provide both class
methods and instance methods, where the object instances each represent
a table record.
dsn
my $string = Padre::DB->dsn;
The "dsn" accessor returns the DBI connection string used to connect to
the SQLite database as a string.
dbh
my $handle = Padre::DB->dbh;
To reliably prevent potential SQLite deadlocks resulting from multiple
connections in a single process, each ORLite package will only ever
maintain a single connection to the database.
During a transaction, this will be the same (cached) database handle.
Although in most situations you should not need a direct DBI connection
handle, the "dbh" method provides a method for getting a direct
connection in a way that is compatible with connection management in
ORLite.
Please note that these connections should be short-lived, you should
never hold onto a connection beyond your immediate scope.
The transaction system in ORLite is specifically designed so that code
using the database should never have to know whether or not it is in a
transation.
Because of this, you should never call the ->disconnect method on the
database handles yourself, as the handle may be that of a currently
running transaction.
Further, you should do your own transaction management on a handle
provided by the <dbh> method.
In cases where there are extreme needs, and you absolutely have to
violate these connection handling rules, you should create your own
completely manual DBI->connect call to the database, using the connect
string provided by the "dsn" method.
The "dbh" method returns a DBI::db object, or throws an exception on
error.
begin
Padre::DB->begin;
The "begin" method indicates the start of a transaction.
In the same way that ORLite allows only a single connection, likewise
it allows only a single application-wide transaction.
No indication is given as to whether you are currently in a transaction
or not, all code should be written neutrally so that it works either
way or doesn't need to care.
Returns true or throws an exception on error.
commit
Padre::DB->commit;
The "commit" method commits the current transaction. If called outside
of a current transaction, it is accepted and treated as a null
operation.
Once the commit has been completed, the database connection falls back
into auto-commit state. If you wish to immediately start another
transaction, you will need to issue a separate ->begin call.
Returns true or throws an exception on error.
rollback
The "rollback" method rolls back the current transaction. If called
outside of a current transaction, it is accepted and treated as a null
operation.
Once the rollback has been completed, the database connection falls
back into auto-commit state. If you wish to immediately start another
transaction, you will need to issue a separate ->begin call.
If a transaction exists at END-time as the process exits, it will be
automatically rolled back.
Returns true or throws an exception on error.
do
Padre::DB->do(
'insert into table ( foo, bar ) values ( ?, ? )', {},
\$foo_value,
\$bar_value,
);
The "do" method is a direct wrapper around the equivalent DBI method,
but applied to the appropriate locally-provided connection or
transaction.
It takes the same parameters and has the same return values and error
behaviour.
selectall_arrayref
The "selectall_arrayref" method is a direct wrapper around the
equivalent DBI method, but applied to the appropriate locally-provided
connection or transaction.
It takes the same parameters and has the same return values and error
behaviour.
selectall_hashref
The "selectall_hashref" method is a direct wrapper around the
equivalent DBI method, but applied to the appropriate locally-provided
connection or transaction.
It takes the same parameters and has the same return values and error
behaviour.
selectcol_arrayref
The "selectcol_arrayref" method is a direct wrapper around the
equivalent DBI method, but applied to the appropriate locally-provided
connection or transaction.
It takes the same parameters and has the same return values and error
behaviour.
selectrow_array
The "selectrow_array" method is a direct wrapper around the equivalent
DBI method, but applied to the appropriate locally-provided connection
or transaction.
It takes the same parameters and has the same return values and error
behaviour.
selectrow_arrayref
The "selectrow_arrayref" method is a direct wrapper around the
equivalent DBI method, but applied to the appropriate locally-provided
connection or transaction.
It takes the same parameters and has the same return values and error
behaviour.
selectrow_hashref
The "selectrow_hashref" method is a direct wrapper around the
equivalent DBI method, but applied to the appropriate locally-provided
connection or transaction.
It takes the same parameters and has the same return values and error
behaviour.
prepare
The "prepare" method is a direct wrapper around the equivalent DBI
method, but applied to the appropriate locally-provided connection or
transaction
It takes the same parameters and has the same return values and error
behaviour.
In general though, you should try to avoid the use of your own prepared
statements if possible, although this is only a recommendation and by
no means prohibited.
pragma
# Get the user_version for the schema
my $version = Padre::DB->pragma('user_version');
The "pragma" method provides a convenient method for fetching a pragma
for a database. See the SQLite documentation for more details.
SUPPORTPadre::DB is based on ORLite.
Documentation created by ORLite::Pod 0.10.
For general support please see the support section of the main project
documentation.
AUTHOR
Adam Kennedy <adamk@cpan.org>
COPYRIGHT
Copyright 2008-2011 The Padre development team as listed in Padre.pm.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
The full text of the license can be found in the LICENSE file included
with this module.
perl v5.14.1 2011-06-18 Padre::DB(3)
