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
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
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:
+See L<DBIx::Class::Manual::Cookbook/Retrieve_one_and_only_one_row_from_a_resultset>.
- ->search->(undef, { order_by => "id DESC" })
-
-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
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.
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
$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">
+
=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 chance 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