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
be alarmed if the error from incorrect connection details happens a
lot later.
+=item .. use DBIx::Class across multiple databases?
-=back
+If your database server allows you to run querys across multiple
+databases at once, then so can DBIx::Class. All you need to do is make
+sure you write the database name as part of the
+L<DBIx::Class::ResultSource/table> call. Eg:
+
+ __PACKAGE__->table('mydb.mytablename');
+
+And load all the Result classes for both / all databases using one
+L<DBIx::Class::Schema/load_namespaces> call.
+
+=item .. use DBIx::Class across PostgreSQL/DB2/Oracle schemas?
+
+Add the name of the schema to the L<DBIx::Class::ResultSource/table>
+as part of the name, and make sure you give the one user you are going
+to connect with rights to read/write all the schemas/tables as
+necessary.
+
+=back
=head2 Relationships
=item .. tell DBIx::Class about relationships between my tables?
-There are a vareity of relationship types that come pre-defined for
+There are a variety of relationship types that come pre-defined for
you to use. These are all listed in L<DBIx::Class::Relationship>. If
you need a non-standard type, or more information, look in
L<DBIx::Class::Relationship::Base>.
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
Read the documentation on L<DBIx::Class::Relationship/many_to_many>.
-=item .. stop DBIx::Class from attempting to cascade deletes on my has_many relationships?
+=item .. stop DBIx::Class from attempting to cascade deletes on my has_many and might_have relationships?
By default, DBIx::Class cascades deletes and updates across
-C<has_many> relationships. If your database already does this (and
-that is probably better), turn it off by supplying C<< cascade_delete => 0 >>
-in the relationship attributes. See L<DBIx::Class::Relationship::Base>.
+C<has_many> and C<might_have> relationships. You can disable this
+behaviour on a per-relationship basis by supplying
+C<< cascade_delete => 0 >> in the relationship attributes.
+
+The cascaded operations are performed after the requested delete or
+update, so if your database has a constraint on the relationship, it
+will have deleted/updated the related records or raised an exception
+before DBIx::Class gets to perform the cascaded operation.
+
+See L<DBIx::Class::Relationship>.
=item .. use a relationship?
->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?
+=item .. search with an SQL function on the left hand side?
+
+To use an SQL function on the left hand side of a comparison:
-To use functions or literal SQL with conditions other than equality
-you need to supply the entire condition, for example:
+ ->search({ -nest => \[ 'YEAR(date_of_birth) = ?', [ plain_value => 1979 ] ] });
- my $interval = "< now() - interval '12 hours'";
- ->search({last_attempt => \$interval})
+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.
-and not:
+Or, if you have quoting off:
- my $interval = "now() - interval '12 hours'";
- ->search({last_attempt => { '<' => \$interval } })
+ ->search({ 'YEAR(date_of_birth)' => 1979 });
=item .. find more help on constructing searches?
L<DBIx::Class::Manual::Cookbook>, try looking in the SQL::Abstract
documentation.
+=item .. make searches in Oracle (10gR2 and newer) case-insensitive?
+
+To make Oracle behave like most RDBMS use on_connect_do to issue
+alter session statements on database connection establishment:
+
+ ->on_connect_do("ALTER SESSION SET NLS_COMP = 'LINGUISTIC'");
+ ->on_connect_do("ALTER SESSION SET NLS_SORT = '<NLS>_CI'");
+ e.g.
+ ->on_connect_do("ALTER SESSION SET NLS_SORT = 'BINARY_CI'");
+ ->on_connect_do("ALTER SESSION SET NLS_SORT = 'GERMAN_CI'");
+
+
=back
=head2 Fetching data
=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:
+See L<DBIx::Class::Manual::Cookbook/Retrieve_one_and_only_one_row_from_a_resultset>.
+
+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)
+
+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?
+
+Use L<DBIx::Class::PK/discard_changes>.
- ->search->(undef, { order_by => "id DESC" })
+ $row->discard_changes
-Then call L<DBIx::Class::ResultSet/slice> and ask it only to return 1 row:
+Discarding changes and refreshing from storage are two sides fo the same coin. When you
+want to discard your local changes, just re-fetch the row from storage. When you want
+to get a new, fresh copy of the row, just re-fetch the 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.
- ->slice(0,1)
+=item .. fetch my data a "page" at a time?
-These two calls can be combined into a single statement:
+Pass the C<rows> and C<page> attributes to your search, eg:
- ->search->(undef, { order_by => "id DESC" })->slice(0,1)
+ ->search({}, { rows => 10, page => 1});
-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.
+=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
inserted key, you can tell it the name of the sequence in the
C<column_info> supplied with C<add_columns>.
- ->add_columns({ id => { sequence => 'mysequence' } });
+ ->add_columns({ id => { sequence => 'mysequence', auto_nextval => 1 } });
=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
->update({ somecolumn => \'othercolumn' })
+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.
+
=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
You can add your own data accessors to your classes.
+One method is to use the built in mk_group_accessors (via L<Class::Accessor::Grouped>)
+
+ package MyTable;
+
+ use parent 'DBIx::Class';
+
+ __PACKAGE__->table('foo'); #etc
+ __PACKAGE__->mk_group_accessors('simple' => qw/non_column_data/); # must use simple group
+
+An another method is to use L<Moose> with your L<DBIx::Class> package.
+
+ package MyTable;
+
+ use Moose; # import Moose
+ use Moose::Util::TypeConstraint; # import Moose accessor type constraints
+
+ extends 'DBIx::Class'; # Moose changes the way we define our parent (base) package
+
+ has 'non_column_data' => ( is => 'rw', isa => 'Str' ); # define a simple attribute
+
+ __PACKAGE__->table('foo'); # etc
+
+With either of these methods the resulting use of the accesssor would be
+
+ my $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
+
+ # some other stuff happens here
+
+ $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
search again or relationship accessors. The SQL query is only run when
you ask the resultset for an actual row object.
+=item How do I deal with tables that lack a primary key?
+
+If your table lacks a primary key, DBIx::Class can't work out which row
+it should operate on, for example to delete or update. However, a
+UNIQUE constraint on one or more columns allows DBIx::Class to uniquely
+identify the row, so you can tell L<DBIx::Class::ResultSource> these
+columns act as a primary key, even if they don't from the database's
+point of view:
+
+ $resultset->set_primary_key(@column);
+
+=item How do I make my program start faster?
+
+Look at the tips in L<DBIx::Class::Manual::Cookbook/"STARTUP SPEED">
+
+=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">
+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
particular column or group of columns (a-la cdbi Stringfy column
group, or stringify_self method) ?
-See L<Cookbook/Stringification>
+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