be alarmed if the error from incorrect connection details happens a
lot later.
+=item .. use DBIx::Class across multiple databases?
+
+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
=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>.
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?
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
+
+(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
+
+Or, if you have quoting off:
+
+ ->search({ 'YEAR(date_of_birth)' => 1979 });
+
=item .. find more help on constructing searches?
Behind the scenes, DBIx::Class uses L<SQL::Abstract> to help construct
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
=over 4
-=item .. fetch as much data as possible in as few select calls as possible? (prefetch)
+=item .. fetch as much data as possible in as few select calls as possible?
See the prefetch examples in the L<Cookbook|DBIx::Class::Manual::Cookbook>.
+=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
+L<Cookbook|DBIx::Class::Manual::Cookbook> for details.
+
+=item .. fetch a formatted column?
+
+In your table schema class, create a "private" column accessor with:
+
+ __PACKAGE__->add_columns(my_column => { accessor => '_hidden_my_column' });
+
+Then, in the same class, implement a subroutine called "my_column" that
+fetches the real value and does the formatting you want.
+
+See the Cookbook for more details.
+
+=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" })
+
+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:
+
+ ->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.
+
+=item .. refresh a row from storage?
+
+Use L<DBIx::Class::PK/discard_changes>.
+
+ $row->discard_changes
+
+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.
+
+=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
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?
->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.
+
+If you want to use JSON, then in your table schema class, do the following:
+
+ use JSON;
+
+ __PACKAGE__->add_columns(qw/ ... my_column ../)
+ __PACKAGE__->inflate_column('my_column', {
+ inflate => sub { jsonToObj(shift) },
+ deflate => sub { objToJson(shift) },
+ });
+
+For YAML, in your table schema class, do the following:
+
+ use YAML;
+
+ __PACKAGE__->add_columns(qw/ ... my_column ../)
+ __PACKAGE__->inflate_column('my_column', {
+ inflate => sub { YAML::Load(shift) },
+ deflate => sub { YAML::Dump(shift) },
+ });
+
+This technique is an easy way to store supplemental unstructured data in a table. Be
+careful not to overuse this capability, however. If you find yourself depending more
+and more on some data within the inflated column, then it may be time to factor that
+data out.
+
=back
=head2 Misc
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 some where 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">
+
=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
projects / dbsrgits/DBIx-Class.git / blobdiff