Next, spend some time defining which data you need to store, and how
it relates to the other data you have. For some help on normalisation,
-go to L<http://b62.tripod.com/doc/dbbase.htm> or
-L<http://209.197.234.36/db/simple.html>.
+go to L<http://b62.tripod.com/doc/dbbase.htm>.
Now, decide whether you want to have the database itself be the
definitive source of information about the data layout, or your
to connect with rights to read/write all the schemas/tables as
necessary.
-=back
+=back
=head2 Relationships
Create a C<belongs_to> relationship for the field containing the
foreign key. See L<DBIx::Class::Relationship/belongs_to>.
-=item .. define a foreign key relationship where the key field may contain NULL?
+=item .. define a foreign key relationship where the key field may contain NULL?
Just create a C<belongs_to> relationship, as above. If the column is
NULL then the inflation to the foreign object will not happen. This
->search({'created_time' => { '>=', '2006-06-01 00:00:00' } })
-Note that to use a function here you need to make the whole value into
-a scalar reference:
+Note that to use a function here you need to make it a scalar
+reference:
- ->search({'created_time' => \'>= yesterday()' })
+ ->search({'created_time' => { '>=', \'yesterday()' } })
=item .. search in several tables simultaneously?
query, which can be accessed similarly to a table, see your database
documentation for details.
-=item .. search using greater-than or less-than and database functions?
-
-To use functions or literal SQL with conditions other than equality
-you need to supply the entire condition, for example:
-
- my $interval = "< now() - interval '12 hours'";
- ->search({last_attempt => \$interval})
-
-and not:
-
- my $interval = "now() - interval '12 hours'";
- ->search({last_attempt => { '<' => \$interval } })
-
=item .. search with an SQL function on the left hand side?
To use an SQL function on the left hand side of a comparison:
- ->search({}, { where => \'YEAR(date_of_birth)=1979' });
-
-=begin hidden
+ ->search({ -nest => \[ 'YEAR(date_of_birth) = ?', [ plain_value => 1979 ] ] });
-(When the bind arg ordering bug is fixed, the previous example can be
-replaced with the following.)
-
- ->search({}, { where => \'YEAR(date_of_birth)=?', bind => [ 1979 ] });
-
-=end hidden
+Note: the C<plain_value> string in the C<< [ plain_value => 1979 ] >> part
+should be either the same as the name of the column (do this if the type of the
+return value of the function is the same as the type of the column) or
+otherwise it's essentially a dummy string currently (use C<plain_value> as a
+habit). It is used by L<DBIx::Class> to handle special column types.
Or, if you have quoting off:
- ->search({ 'YEAR(date_of_birth' => 1979 });
+ ->search({ 'YEAR(date_of_birth)' => 1979 });
=item .. find more help on constructing searches?
=item .. fetch a whole column of data instead of a row?
-Call C<get_column> on a L<DBIx::Class::ResultSet>, this returns a
-L<DBIx::Class::ResultSetColumn>, see it's documentation and the
+Call C<get_column> on a L<DBIx::Class::ResultSet>. This returns a
+L<DBIx::Class::ResultSetColumn>. See its documentation and the
L<Cookbook|DBIx::Class::Manual::Cookbook> for details.
=item .. fetch a formatted column?
=item .. fetch a single (or topmost) row?
-Sometimes you many only want a single record back from a search. A quick
-way to get that single row is to first run your search as usual:
-
- ->search->(undef, { order_by => "id DESC" })
+See L<DBIx::Class::Manual::Cookbook/Retrieve_one_and_only_one_row_from_a_resultset>.
-Then call L<DBIx::Class::ResultSet/slice> and ask it only to return 1 row:
-
- ->slice(0)
-
-These two calls can be combined into a single statement:
+A less readable way is to ask a regular search to return 1 row, using
+L<DBIx::Class::ResultSet/slice>:
->search->(undef, { order_by => "id DESC" })->slice(0)
-Why slice instead of L<DBIx::Class::ResultSet/first> or L<DBIx::Class::ResultSet/single>?
-If supported by the database, slice will use LIMIT/OFFSET to hint to the database that we
-really only need one row. This can result in a significant speed improvement.
+which (if supported by the database) will use LIMIT/OFFSET to hint to the
+database that we really only need one row. This can result in a significant
+speed improvement. The method using L<DBIx::Class::ResultSet/single> mentioned
+in the cookbook can do the same if you pass a C<rows> attribute to the search.
=item .. refresh a row from storage?
L<DBIx::Class::PK/discard_changes> does just that by re-fetching the row from storage
using the row's primary key.
+=item .. fetch my data a "page" at a time?
+
+Pass the C<rows> and C<page> attributes to your search, eg:
+
+ ->search({}, { rows => 10, page => 1});
+
+=item .. get a count of all rows even when paging?
+
+Call C<pager> on the paged resultset, it will return a L<Data::Page>
+object. Calling C<total_entries> on the pager will return the correct
+total.
+
+C<count> on the resultset will only return the total number in the page.
+
=back
=head2 Inserting and updating data
=item .. insert many rows of data efficiently?
+The C<populate> method in L<DBIx::Class::ResultSet> provides
+efficient bulk inserts.
+
=item .. update a collection of rows at the same time?
Create a resultset using a search, to filter the rows of data you
But note that when using a scalar reference the column in the database
will be updated but when you read the value from the object with e.g.
-
+
->somecolumn()
-
+
you still get back the scalar reference to the string, B<not> the new
value in the database. To get that you must refresh the row from storage
using C<discard_changes()>. Or chain your function calls like this:
->update->discard_changes
-
- to update the database and refresh the object in one step.
-
+
+to update the database and refresh the object in one step.
+
=item .. store JSON/YAML in a column and have it deflate/inflate automatically?
You can use L<DBIx::Class::InflateColumn> to accomplish YAML/JSON storage transparently.
=back
+=head2 Custom methods in Result classes
+
+You can add custom methods that do arbitrary things, even to unrelated tables.
+For example, to provide a C<< $book->foo() >> method which searches the
+cd table, you'd could add this to Book.pm:
+
+ sub foo {
+ my ($self, $col_data) = @_;
+ return $self->result_source->schema->resultset('cd')->search($col_data);
+ }
+
+And invoke that on any Book Result object like so:
+
+ my $rs = $book->foo({ title => 'Down to Earth' });
+
+When two tables ARE related, L<DBIx::Class::Relationship::Base> provides many
+methods to find or create data in related tables for you. But if you want to
+write your own methods, you can.
+
+For example, to provide a C<< $book->foo() >> method to manually implement
+what create_related() from L<DBIx::Class::Relationship::Base> does, you could
+add this to Book.pm:
+
+ sub foo {
+ my ($self, $relname, $col_data) = @_;
+ return $self->related_resultset($relname)->create($col_data);
+ }
+
+Invoked like this:
+
+ my $author = $book->foo('author', { name => 'Fred' });
+
=head2 Misc
=over 4
package MyTable;
use Moose; # import Moose
- use Moose::Util::TypeConstraint; # import Moose accessor type constraints
+ use Moose::Util::TypeConstraint; # import Moose accessor type constraints
extends 'DBIx::Class'; # Moose changes the way we define our parent (base) package
my $row;
- # assume that some where in here $row will get assigned to a MyTable row
+ # assume that somewhere in here $row will get assigned to a MyTable row
$row->non_column_data('some string'); # would set the non_column_data accessor
$row->update(); # would not inline the non_column_data accessor into the update
-
+
=item How do I use DBIx::Class objects in my TT templates?
Like normal objects, mostly. However you need to watch out for TT
=item How do I reduce the overhead of database queries?
You can reduce the overhead of object creation within L<DBIx::Class>
-using the tips in L<DBIx::Class::Manual::Cookbook/"Skip row object creation for faster results">
+using the tips in L<DBIx::Class::Manual::Cookbook/"Skip row object creation for faster results">
and L<DBIx::Class::Manual::Cookbook/"Get raw data for blindingly fast results">
+=item How do I override a run time method (e.g. a relationship accessor)?
+
+If you need access to the original accessor, then you must "wrap around" the original method.
+You can do that either with L<Moose::Manual::MethodModifiers> or L<Class::Method::Modifiers>.
+The code example works for both modules:
+
+ package Your::Schema::Group;
+ use Class::Method::Modifiers;
+
+ # ... declare columns ...
+
+ __PACKAGE__->has_many('group_servers', 'Your::Schema::GroupServer', 'group_id');
+ __PACKAGE__->many_to_many('servers', 'group_servers', 'server');
+
+ # if the server group is a "super group", then return all servers
+ # otherwise return only servers that belongs to the given group
+ around 'servers' => sub {
+ my $orig = shift;
+ my $self = shift;
+
+ return $self->$orig(@_) unless $self->is_super_group;
+ return $self->result_source->schema->resultset('Server')->all;
+ };
+
+If you just want to override the original method, and don't care about the data
+from the original accessor, then you have two options. Either use
+L<Method::Signatures::Simple> that does most of the work for you, or do
+it the "dirty way".
+
+L<Method::Signatures::Simple> way:
+
+ package Your::Schema::Group;
+ use Method::Signatures::Simple;
+
+ # ... declare columns ...
+
+ __PACKAGE__->has_many('group_servers', 'Your::Schema::GroupServer', 'group_id');
+ __PACKAGE__->many_to_many('servers', 'group_servers', 'server');
+
+ # The method keyword automatically injects the annoying my $self = shift; for you.
+ method servers {
+ return $self->result_source->schema->resultset('Server')->search({ ... });
+ }
+
+The dirty way:
+
+ package Your::Schema::Group;
+ use Sub::Name;
+
+ # ... declare columns ...
+
+ __PACKAGE__->has_many('group_servers', 'Your::Schema::GroupServer', 'group_id');
+ __PACKAGE__->many_to_many('servers', 'group_servers', 'server');
+
+ *servers = subname servers => sub {
+ my $self = shift;
+ return $self->result_source->schema->resultset('Server')->search({ ... });
+ };
+
=back
=head2 Notes for CDBI users
See L<DBIx::Class::Manual::Cookbook/Stringification>
=back
+
+=head2 Troubleshooting
+
+=over 4
+
+=item Help, I can't connect to postgresql!
+
+If you get an error such as:
+
+ DBI connect('dbname=dbic','user',...) failed: could not connect to server:
+ No such file or directory Is the server running locally and accepting
+ connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
+
+Likely you have/had two copies of postgresql installed simultaneously, the
+second one will use a default port of 5433, while L<DBD::Pg> is compiled with a
+default port of 5432.
+
+You can change the port setting in C<postgresql.conf>.
+
+=item I've lost or forgotten my mysql password
+
+Stop mysqld and restart it with the --skip-grant-tables option.
+
+Issue the following statements in the mysql client.
+
+ UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root';
+ FLUSH PRIVILEGES;
+
+Restart mysql.
+
+Taken from:
+
+L<http://dev.mysql.com/doc/refman/5.1/en/resetting-permissions.html>.
+
+=back
projects / dbsrgits/DBIx-Class.git / blobdiff