NAME

DBIx::Class::ResultSet - Represents a query used for fetching a set of results.

SYNOPSIS

my $users_rs   = $schema->resultset('User');
while( $user = $users_rs->next) {
  print $user->username;
}

my $registered_users_rs   = $schema->resultset('User')->search({ registered => 1 });
my @cds_in_2005 = $schema->resultset('CD')->search({ year => 2005 })->all();

DESCRIPTION

A ResultSet is an object which stores a set of conditions representing a query. It is the backbone of DBIx::Class (i.e. the really important/useful bit).

No SQL is executed on the database when a ResultSet is created, it just stores all the conditions needed to create the query.

A basic ResultSet representing the data of an entire table is returned by calling resultset on a DBIx::Class::Schema and passing in a Source name.

my $users_rs = $schema->resultset('User');

A new ResultSet is returned from calling "search" on an existing ResultSet. The new one will contain all the conditions of the original, plus any new conditions added in the search call.

A ResultSet also incorporates an implicit iterator. "next" and "reset" can be used to walk through all the DBIx::Class::Rows the ResultSet represents.

The query that the ResultSet represents is only executed against the database when these methods are called: "find", "next", "all", "first", "single", "count".

If a resultset is used in a numeric context it returns the "count". However, if it is used in a boolean context it is always true. So if you want to check if a resultset has any results, you must use if $rs != 0.

EXAMPLES

Chaining resultsets

Let's say you've got a query that needs to be run to return some data to the user. But, you have an authorization system in place that prevents certain users from seeing certain information. So, you want to construct the basic query in one method, but add constraints to it in another.

sub get_data {
  my $self = shift;
  my $request = $self->get_request; # Get a request object somehow.
  my $schema = $self->get_schema;   # Get the DBIC schema object somehow.

  my $cd_rs = $schema->resultset('CD')->search({
    title => $request->param('title'),
    year => $request->param('year'),
  });

  $cd_rs = $self->apply_security_policy( $cd_rs );

  return $cd_rs->all();
}

sub apply_security_policy {
  my $self = shift;
  my ($rs) = @_;

  return $rs->search({
    subversive => 0,
  });
}

Resolving conditions and attributes

When a resultset is chained from another resultset, conditions and attributes with the same keys need resolving.

"join", "prefetch", "+select", "+as" attributes are merged into the existing ones from the original resultset.

The "where" and "having" attributes, and any search conditions, are merged with an SQL AND to the existing condition from the original resultset.

All other attributes are overridden by any new ones supplied in the search attributes.

Multiple queries

Since a resultset just defines a query, you can do all sorts of things with it with the same object.

# Don't hit the DB yet.
my $cd_rs = $schema->resultset('CD')->search({
  title => 'something',
  year => 2009,
});

# Each of these hits the DB individually.
my $count = $cd_rs->count;
my $most_recent = $cd_rs->get_column('date_released')->max();
my @records = $cd_rs->all;

And it's not just limited to SELECT statements.

$cd_rs->delete();

This is even cooler:

$cd_rs->create({ artist => 'Fred' });

Which is the same as:

$schema->resultset('CD')->create({
  title => 'something',
  year => 2009,
  artist => 'Fred'
});

See: "search", "count", "get_column", "all", "create".

METHODS

new

Arguments: $source, \%$attrs
Return Value: $rs

The resultset constructor. Takes a source object (usually a DBIx::Class::ResultSourceProxy::Table) and an attribute hash (see "ATTRIBUTES" below). Does not perform any queries -- these are executed as needed by the other methods.

Generally you won't need to construct a resultset manually. You'll automatically get one from e.g. a "search" called in scalar context:

my $rs = $schema->resultset('CD')->search({ title => '100th Window' });

IMPORTANT: If called on an object, proxies to new_result instead so

my $cd = $schema->resultset('CD')->new({ title => 'Spoon' });

will return a CD object, not a ResultSet.

search

Arguments: $cond, \%attrs?
Return Value: $resultset (scalar context) || @row_objs (list context)

my @cds    = $cd_rs->search({ year => 2001 }); # "... WHERE year = 2001"
my $new_rs = $cd_rs->search({ year => 2005 });

my $new_rs = $cd_rs->search([ { year => 2005 }, { year => 2004 } ]);
               # year = 2005 OR year = 2004

In list context, ->all() is called implicitly on the resultset, thus returning a list of row objects instead. To avoid that, use "search_rs".

If you need to pass in additional attributes but no additional condition, call it as search(undef, \%attrs).

# "SELECT name, artistid FROM $artist_table"
my @all_artists = $schema->resultset('Artist')->search(undef, {
  columns => [qw/name artistid/],
});

For a list of attributes that can be passed to search, see "ATTRIBUTES". For more examples of using this function, see Searching. For a complete documentation for the first argument, see SQL::Abstract.

For more help on using joins with search, see DBIx::Class::Manual::Joining.

CAVEAT

Note that "search" does not process/deflate any of the values passed in the SQL::Abstract-compatible search condition structure. This is unlike other condition-bound methods "new", "create" and "find". The user must ensure manually that any value passed to this method will stringify to something the RDBMS knows how to deal with. A notable example is the handling of DateTime objects, for more info see: "Formatting_DateTime_objects_in_queries" in DBIx::Class::Manual::Cookbook.

search_rs

Arguments: $cond, \%attrs?
Return Value: $resultset

This method does the same exact thing as search() except it will always return a resultset, even in list context.

search_literal

Arguments: $sql_fragment, @bind_values
Return Value: $resultset (scalar context) || @row_objs (list context)

my @cds   = $cd_rs->search_literal('year = ? AND title = ?', qw/2001 Reload/);
my $newrs = $artist_rs->search_literal('name = ?', 'Metallica');

Pass a literal chunk of SQL to be added to the conditional part of the resultset query.

CAVEAT: search_literal is provided for Class::DBI compatibility and should only be used in that context. search_literal is a convenience method. It is equivalent to calling $schema->search(\[]), but if you want to ensure columns are bound correctly, use search.

Example of how to use search instead of search_literal

my @cds = $cd_rs->search_literal('cdid = ? AND (artist = ? OR artist = ?)', (2, 1, 2));
my @cds = $cd_rs->search(\[ 'cdid = ? AND (artist = ? OR artist = ?)', [ 'cdid', 2 ], [ 'artist', 1 ], [ 'artist', 2 ] ]);

See "Searching" in DBIx::Class::Manual::Cookbook and "Searching" in DBIx::Class::Manual::FAQ for searching techniques that do not require search_literal.

find

Arguments: \%columns_values | @pk_values, \%attrs?
Return Value: $row_object | undef

Finds and returns a single row based on supplied criteria. Takes either a hashref with the same format as "create" (including inference of foreign keys from related objects), or a list of primary key values in the same order as the primary columns declaration on the "result_source".

In either case an attempt is made to combine conditions already existing on the resultset with the condition passed to this method.

To aid with preparing the correct query for the storage you may supply the key attribute, which is the name of a unique constraint (the unique constraint corresponding to the primary columns is always named primary). If the key attribute has been supplied, and DBIC is unable to construct a query that satisfies the named unique constraint fully ( non-NULL values for each column member of the constraint) an exception is thrown.

If no key is specified, the search is carried over all unique constraints which are fully defined by the available condition.

If no such constraint is found, find currently defaults to a simple search->(\%column_values) which may or may not do what you expect. Note that this fallback behavior may be deprecated in further versions. If you need to search with arbitrary conditions - use "search". If the query resulting from this fallback produces more than one row, a warning to the effect is issued, though only the first row is constructed and returned as $row_object.

In addition to key, "find" recognizes and applies standard resultset attributes in the same way as "search" does.

Note that if you have extra concerns about the correctness of the resulting query you need to specify the key attribute and supply the entire condition as an argument to find (since it is not always possible to perform the combination of the resultset condition with the supplied one, especially if the resultset condition contains literal sql).

For example, to find a row by its primary key:

my $cd = $schema->resultset('CD')->find(5);

You can also find a row by a specific unique constraint:

my $cd = $schema->resultset('CD')->find(
  {
    artist => 'Massive Attack',
    title  => 'Mezzanine',
  },
  { key => 'cd_artist_title' }
);

See also "find_or_create" and "update_or_create".

search_related

Arguments: $rel, $cond, \%attrs?
Return Value: $new_resultset (scalar context) || @row_objs (list context)

$new_rs = $cd_rs->search_related('artist', {
  name => 'Emo-R-Us',
});

Searches the specified relationship, optionally specifying a condition and attributes for matching records. See "ATTRIBUTES" for more information.

In list context, ->all() is called implicitly on the resultset, thus returning a list of row objects instead. To avoid that, use "search_related_rs".

search_related_rs

This method works exactly the same as search_related, except that it guarantees a resultset, even in list context.

cursor

Arguments: none
Return Value: $cursor

Returns a storage-driven cursor to the given resultset. See DBIx::Class::Cursor for more information.

single

Arguments: $cond?
Return Value: $row_object | undef

my $cd = $schema->resultset('CD')->single({ year => 2001 });

Inflates the first result without creating a cursor if the resultset has any records in it; if not returns undef. Used by "find" as a lean version of "search".

While this method can take an optional search condition (just like "search") being a fast-code-path it does not recognize search attributes. If you need to add extra joins or similar, call "search" and then chain-call "single" on the DBIx::Class::ResultSet returned.

Note

As of 0.08100, this method enforces the assumption that the preceding query returns only one row. If more than one row is returned, you will receive a warning:

Query returned more than one row

In this case, you should be using "next" or "find" instead, or if you really know what you are doing, use the "rows" attribute to explicitly limit the size of the resultset.

This method will also throw an exception if it is called on a resultset prefetching has_many, as such a prefetch implies fetching multiple rows from the database in order to assemble the resulting object.

get_column

Arguments: $cond?
Return Value: $resultsetcolumn

my $max_length = $rs->get_column('length')->max;

Returns a DBIx::Class::ResultSetColumn instance for a column of the ResultSet.

search_like

Arguments: $cond, \%attrs?
Return Value: $resultset (scalar context) || @row_objs (list context)

# WHERE title LIKE '%blue%'
$cd_rs = $rs->search_like({ title => '%blue%'});

Performs a search, but uses LIKE instead of = as the condition. Note that this is simply a convenience method retained for ex Class::DBI users. You most likely want to use "search" with specific operators.

For more information, see DBIx::Class::Manual::Cookbook.

This method is deprecated and will be removed in 0.09. Use "search()" instead. An example conversion is:

->search_like({ foo => 'bar' });

# Becomes

->search({ foo => { like => 'bar' } });

slice

Arguments: $first, $last
Return Value: $resultset (scalar context) || @row_objs (list context)

Returns a resultset or object list representing a subset of elements from the resultset slice is called on. Indexes are from 0, i.e., to get the first three records, call:

my ($one, $two, $three) = $rs->slice(0, 2);

Arguments: none
Return Value: $result | undef

Returns the next element in the resultset (undef is there is none).

Can be used to efficiently iterate over records in the resultset:

my $rs = $schema->resultset('CD')->search;
while (my $cd = $rs->next) {
  print $cd->title;
}

Note that you need to store the resultset object, and call next on it. Calling resultset('Table')->next repeatedly will always return the first record from the resultset.

result_source

Arguments: $result_source?
Return Value: $result_source

An accessor for the primary ResultSource object from which this ResultSet is derived.

result_class

Arguments: $result_class?
Return Value: $result_class

An accessor for the class to use when creating row objects. Defaults to result_source->result_class - which in most cases is the name of the "table" class.

Note that changing the result_class will also remove any components that were originally loaded in the source class via "load_components" in DBIx::Class::ResultSource. Any overloaded methods in the original source class will not run.

count

Arguments: $cond, \%attrs??
Return Value: $count

Performs an SQL COUNT with the same query as the resultset was built with to find the number of elements. Passing arguments is equivalent to $rs->search ($cond, \%attrs)->count

count_rs

Arguments: $cond, \%attrs??
Return Value: $count_rs

Same as "count" but returns a DBIx::Class::ResultSetColumn object. This can be very handy for subqueries:

->search( { amount => $some_rs->count_rs->as_query } )

As with regular resultsets the SQL query will be executed only after the resultset is accessed via "next" or "all". That would return the same single value obtainable via "count".

count_literal

Arguments: $sql_fragment, @bind_values
Return Value: $count

Counts the results in a literal query. Equivalent to calling "search_literal" with the passed arguments, then "count".

all

Arguments: none
Return Value: @objects

Returns all elements in the resultset.

reset

Arguments: none
Return Value: $self

Resets the resultset's cursor, so you can iterate through the elements again. Implicitly resets the storage cursor, so a subsequent "next" will trigger another query.

first

Arguments: none
Return Value: $object | undef

Resets the resultset and returns an object for the first result (or undef if the resultset is empty).

update

Arguments: \%values
Return Value: $storage_rv

Sets the specified columns in the resultset to the supplied values in a single query. Note that this will not run any accessor/set_column/update triggers, nor will it update any row object instances derived from this resultset (this includes the contents of the resultset cache if any). See "update_all" if you need to execute any on-update triggers or cascades defined either by you or a result component.

The return value is a pass through of what the underlying storage backend returned, and may vary. See "execute" in DBI for the most common case.

CAVEAT

Note that "update" does not process/deflate any of the values passed in. This is unlike the corresponding "update" in DBIx::Class::Row. The user must ensure manually that any value passed to this method will stringify to something the RDBMS knows how to deal with. A notable example is the handling of DateTime objects, for more info see: "Formatting_DateTime_objects_in_queries" in DBIx::Class::Manual::Cookbook.

update_all

Arguments: \%values
Return Value: 1

Fetches all objects and updates them one at a time via "update" in DBIx::Class::Row. Note that update_all will run DBIC defined triggers, while "update" will not.

delete

Arguments: none
Return Value: $storage_rv

Deletes the rows matching this resultset in a single query. Note that this will not run any delete triggers, nor will it alter the in_storage status of any row object instances derived from this resultset (this includes the contents of the resultset cache if any). See "delete_all" if you need to execute any on-delete triggers or cascades defined either by you or a result component.

The return value is a pass through of what the underlying storage backend returned, and may vary. See "execute" in DBI for the most common case.

delete_all

Arguments: none
Return Value: 1

Fetches all objects and deletes them one at a time via "delete" in DBIx::Class::Row. Note that delete_all will run DBIC defined triggers, while "delete" will not.

populate

Arguments: \@data;

Accepts either an arrayref of hashrefs or alternatively an arrayref of arrayrefs. For the arrayref of hashrefs style each hashref should be a structure suitable for submitting to a $resultset->create(...) method.

In void context, insert_bulk in DBIx::Class::Storage::DBI is used to insert the data, as this is a faster method.

Otherwise, each set of data is inserted into the database using "create" in DBIx::Class::ResultSet, and the resulting objects are accumulated into an array. The array itself, or an array reference is returned depending on scalar or list context.

Example: Assuming an Artist Class that has many CDs Classes relating:

my $Artist_rs = $schema->resultset("Artist");

## Void Context Example
$Artist_rs->populate([
   { artistid => 4, name => 'Manufactured Crap', cds => [
      { title => 'My First CD', year => 2006 },
      { title => 'Yet More Tweeny-Pop crap', year => 2007 },
    ],
   },
   { artistid => 5, name => 'Angsty-Whiny Girl', cds => [
      { title => 'My parents sold me to a record company', year => 2005 },
      { title => 'Why Am I So Ugly?', year => 2006 },
      { title => 'I Got Surgery and am now Popular', year => 2007 }
    ],
   },
]);

## Array Context Example
my ($ArtistOne, $ArtistTwo, $ArtistThree) = $Artist_rs->populate([
  { name => "Artist One"},
  { name => "Artist Two"},
  { name => "Artist Three", cds=> [
  { title => "First CD", year => 2007},
  { title => "Second CD", year => 2008},
]}
]);

print $ArtistOne->name; ## response is 'Artist One'
print $ArtistThree->cds->count ## reponse is '2'

For the arrayref of arrayrefs style, the first element should be a list of the fieldsnames to which the remaining elements are rows being inserted. For example:

$Arstist_rs->populate([
  [qw/artistid name/],
  [100, 'A Formally Unknown Singer'],
  [101, 'A singer that jumped the shark two albums ago'],
  [102, 'An actually cool singer'],
]);

Please note an important effect on your data when choosing between void and wantarray context. Since void context goes straight to insert_bulk in DBIx::Class::Storage::DBI this will skip any component that is overriding insert. So if you are using something like DBIx-Class-UUIDColumns to create primary keys for you, you will find that your PKs are empty. In this case you will have to use the wantarray context in order to create those values.

Arguments: none
Return Value: $pager

Return Value a Data::Page object for the current resultset. Only makes sense for queries with a page attribute.

To get the full count of entries for a paged resultset, call total_entries on the Data::Page object.

new_result

Arguments: \%vals
Return Value: $rowobject

Creates a new row object in the resultset's result class and returns it. The row is not inserted into the database at this point, call "insert" in DBIx::Class::Row to do that. Calling "in_storage" in DBIx::Class::Row will tell you whether the row object has been inserted or not.

Passes the hashref of input on to "new" in DBIx::Class::Row.

as_query

Arguments: none
Return Value: \[ $sql, @bind ]

Returns the SQL query and bind vars associated with the invocant.

This is generally used as the RHS for a subquery.

find_or_new

Arguments: \%vals, \%attrs?
Return Value: $rowobject

my $artist = $schema->resultset('Artist')->find_or_new(
  { artist => 'fred' }, { key => 'artists' });

$cd->cd_to_producer->find_or_new({ producer => $producer },
                                 { key => 'primary });

Find an existing record from this resultset using "find". if none exists, instantiate a new result object and return it. The object will not be saved into your storage until you call "insert" in DBIx::Class::Row on it.

You most likely want this method when looking for existing rows using a unique constraint that is not the primary key, or looking for related rows.

If you want objects to be saved immediately, use "find_or_create" instead.

Note: Make sure to read the documentation of "find" and understand the significance of the key attribute, as its lack may skew your search, and subsequently result in spurious new objects.

Note: Take care when using find_or_new with a table having columns with default values that you intend to be automatically supplied by the database (e.g. an auto_increment primary key column). In normal usage, the value of such columns should NOT be included at all in the call to find_or_new, even when set to undef.

create

Arguments: \%vals
Return Value: a DBIx::Class::Row $object

Attempt to create a single new row or a row with multiple related rows in the table represented by the resultset (and related tables). This will not check for duplicate rows before inserting, use "find_or_create" to do that.

To create one row for this resultset, pass a hashref of key/value pairs representing the columns of the table and the values you wish to store. If the appropriate relationships are set up, foreign key fields can also be passed an object representing the foreign row, and the value will be set to its primary key.

To create related objects, pass a hashref of related-object column values keyed on the relationship name. If the relationship is of type multi ("has_many" in DBIx::Class::Relationship) - pass an arrayref of hashrefs. The process will correctly identify columns holding foreign keys, and will transparently populate them from the keys of the corresponding relation. This can be applied recursively, and will work correctly for a structure with an arbitrary depth and width, as long as the relationships actually exists and the correct column data has been supplied.

Instead of hashrefs of plain related data (key/value pairs), you may also pass new or inserted objects. New objects (not inserted yet, see "new"), will be inserted into their appropriate tables.

Effectively a shortcut for ->new_result(\%vals)->insert.

Example of creating a new row.

$person_rs->create({
  name=>"Some Person",
  email=>"somebody@someplace.com"
});

Example of creating a new row and also creating rows in a related has_many or has_one resultset. Note Arrayref.

$artist_rs->create(
   { artistid => 4, name => 'Manufactured Crap', cds => [
      { title => 'My First CD', year => 2006 },
      { title => 'Yet More Tweeny-Pop crap', year => 2007 },
    ],
   },
);

Example of creating a new row and also creating a row in a related belongs_to resultset. Note Hashref.

$cd_rs->create({
  title=>"Music for Silly Walks",
  year=>2000,
  artist => {
    name=>"Silly Musician",
  }
});

WARNING: When subclassing ResultSet never attempt to override this method. Since it is a simple shortcut for $self->new_result($attrs)->insert, a lot of the internals simply never call it, so your override will be bypassed more often than not. Override either new or insert depending on how early in the "create" process you need to intervene.

find_or_create

Arguments: \%vals, \%attrs?
Return Value: $rowobject

$cd->cd_to_producer->find_or_create({ producer => $producer },
                                    { key => 'primary' });

Tries to find a record based on its primary key or unique constraints; if none is found, creates one and returns that instead.

my $cd = $schema->resultset('CD')->find_or_create({
  cdid   => 5,
  artist => 'Massive Attack',
  title  => 'Mezzanine',
  year   => 2005,
});

Also takes an optional key attribute, to search by a specific key or unique constraint. For example:

my $cd = $schema->resultset('CD')->find_or_create(
  {
    artist => 'Massive Attack',
    title  => 'Mezzanine',
  },
  { key => 'cd_artist_title' }
);

Note: Make sure to read the documentation of "find" and understand the significance of the key attribute, as its lack may skew your search, and subsequently result in spurious row creation.

Note: Because find_or_create() reads from the database and then possibly inserts based on the result, this method is subject to a race condition. Another process could create a record in the table after the find has completed and before the create has started. To avoid this problem, use find_or_create() inside a transaction.

Note: Take care when using find_or_create with a table having columns with default values that you intend to be automatically supplied by the database (e.g. an auto_increment primary key column). In normal usage, the value of such columns should NOT be included at all in the call to find_or_create, even when set to undef.

See also "find" and "update_or_create". For information on how to declare unique constraints, see "add_unique_constraint" in DBIx::Class::ResultSource.

update_or_create

Arguments: \%col_values, { key => $unique_constraint }?
Return Value: $row_object

$resultset->update_or_create({ col => $val, ... });

Like "find_or_create", but if a row is found it is immediately updated via $found_row->update (\%col_values).

Takes an optional key attribute to search on a specific unique constraint. For example:

# In your application
my $cd = $schema->resultset('CD')->update_or_create(
  {
    artist => 'Massive Attack',
    title  => 'Mezzanine',
    year   => 1998,
  },
  { key => 'cd_artist_title' }
);

$cd->cd_to_producer->update_or_create({
  producer => $producer,
  name => 'harry',
}, {
  key => 'primary',
});

Note: Make sure to read the documentation of "find" and understand the significance of the key attribute, as its lack may skew your search, and subsequently result in spurious row creation.

Note: Take care when using update_or_create with a table having columns with default values that you intend to be automatically supplied by the database (e.g. an auto_increment primary key column). In normal usage, the value of such columns should NOT be included at all in the call to update_or_create, even when set to undef.

See also "find" and "find_or_create". For information on how to declare unique constraints, see "add_unique_constraint" in DBIx::Class::ResultSource.

update_or_new

Arguments: \%col_values, { key => $unique_constraint }?
Return Value: $rowobject

$resultset->update_or_new({ col => $val, ... });

Like "find_or_new" but if a row is found it is immediately updated via $found_row->update (\%col_values).

For example:

# In your application
my $cd = $schema->resultset('CD')->update_or_new(
  {
    artist => 'Massive Attack',
    title  => 'Mezzanine',
    year   => 1998,
  },
  { key => 'cd_artist_title' }
);

if ($cd->in_storage) {
    # the cd was updated
}
else {
    # the cd is not yet in the database, let's insert it
    $cd->insert;
}

Note: Make sure to read the documentation of "find" and understand the significance of the key attribute, as its lack may skew your search, and subsequently result in spurious new objects.

Note: Take care when using update_or_new with a table having columns with default values that you intend to be automatically supplied by the database (e.g. an auto_increment primary key column). In normal usage, the value of such columns should NOT be included at all in the call to update_or_new, even when set to undef.

See also "find", "find_or_create" and "find_or_new".

get_cache

Arguments: none
Return Value: \@cache_objects | undef

Gets the contents of the cache for the resultset, if the cache is set.

The cache is populated either by using the "prefetch" attribute to "search" or by calling "set_cache".

set_cache

Arguments: \@cache_objects
Return Value: \@cache_objects

Sets the contents of the cache for the resultset. Expects an arrayref of objects of the same class as those produced by the resultset. Note that if the cache is set the resultset will return the cached objects rather than re-querying the database even if the cache attr is not set.

The contents of the cache can also be populated by using the "prefetch" attribute to "search".

clear_cache

Arguments: none
Return Value: undef

Clears the cache for the resultset.

is_paged

Arguments: none
Return Value: true, if the resultset has been paginated

is_ordered

Arguments: none
Return Value: true, if the resultset has been ordered with order_by.

related_resultset

Arguments: $relationship_name
Return Value: $resultset

Returns a related resultset for the supplied relationship name.

$artist_rs = $schema->resultset('CD')->related_resultset('Artist');

current_source_alias

Arguments: none
Return Value: $source_alias

Returns the current table alias for the result source this resultset is built on, that will be used in the SQL query. Usually it is me.

Currently the source alias that refers to the result set returned by a "search"/"find" family method depends on how you got to the resultset: it's me by default, but eg. "search_related" aliases it to the related result source name (and keeps me referring to the original result set). The long term goal is to make DBIx::Class always alias the current resultset as me (and make this method unnecessary).

Thus it's currently necessary to use this method in predefined queries (see "Predefined searches" in DBIx::Class::Manual::Cookbook) when referring to the source alias of the current result set:

# in a result set class
sub modified_by {
  my ($self, $user) = @_;

  my $me = $self->current_source_alias;

  return $self->search(
    "$me.modified" => $user->id,
  );
}

as_subselect_rs

Arguments: none
Return Value: $resultset

Act as a barrier to SQL symbols. The resultset provided will be made into a "virtual view" by including it as a subquery within the from clause. From this point on, any joined tables are inaccessible to ->search on the resultset (as if it were simply where-filtered without joins). For example:

my $rs = $schema->resultset('Bar')->search({'x.name' => 'abc'},{ join => 'x' });

# 'x' now pollutes the query namespace

# So the following works as expected
my $ok_rs = $rs->search({'x.other' => 1});

# But this doesn't: instead of finding a 'Bar' related to two x rows (abc and
# def) we look for one row with contradictory terms and join in another table
# (aliased 'x_2') which we never use
my $broken_rs = $rs->search({'x.name' => 'def'});

my $rs2 = $rs->as_subselect_rs;

# doesn't work - 'x' is no longer accessible in $rs2, having been sealed away
my $not_joined_rs = $rs2->search({'x.other' => 1});

# works as expected: finds a 'table' row related to two x rows (abc and def)
my $correctly_joined_rs = $rs2->search({'x.name' => 'def'});

Another example of when one might use this would be to select a subset of columns in a group by clause:

my $rs = $schema->resultset('Bar')->search(undef, {
  group_by => [qw{ id foo_id baz_id }],
})->as_subselect_rs->search(undef, {
  columns => [qw{ id foo_id }]
});

In the above example normally columns would have to be equal to the group by, but because we isolated the group by into a subselect the above works.

throw_exception

See "throw_exception" in DBIx::Class::Schema for details.

ATTRIBUTES

Attributes are used to refine a ResultSet in various ways when searching for data. They can be passed to any method which takes an \%attrs argument. See "search", "search_rs", "find", "count".

These are in no particular order:

order_by

Value: ( $order_by | \@order_by | \%order_by )

Which column(s) to order the results by.

[The full list of suitable values is documented in "ORDER BY CLAUSES" in SQL::Abstract; the following is a summary of common options.]

If a single column name, or an arrayref of names is supplied, the argument is passed through directly to SQL. The hashref syntax allows for connection-agnostic specification of ordering direction:

For descending order:

 order_by => { -desc => [qw/col1 col2 col3/] }

For explicit ascending order:

 order_by => { -asc => 'col' }

The old scalarref syntax (i.e. order_by => \'year DESC') is still supported, although you are strongly encouraged to use the hashref syntax as outlined above.

columns

Value: \@columns

Shortcut to request a particular set of columns to be retrieved. Each column spec may be a string (a table column name), or a hash (in which case the key is the as value, and the value is used as the select expression). Adds me. onto the start of any column without a . in it and sets select from that, then auto-populates as from select as normal. (You may also use the cols attribute, as in earlier versions of DBIC.)

Essentially columns does the same as "select" and "as".

columns => [ 'foo', { bar => 'baz' } ]

is the same as

select => [qw/foo baz/],
as => [qw/foo bar/]

+columns

Value: \@columns

Indicates additional columns to be selected from storage. Works the same as "columns" but adds columns to the selection. (You may also use the include_columns attribute, as in earlier versions of DBIC). For example:-

$schema->resultset('CD')->search(undef, {
  '+columns' => ['artist.name'],
  join => ['artist']
});

would return all CDs and include a 'name' column to the information passed to object inflation. Note that the 'artist' is the name of the column (or relationship) accessor, and 'name' is the name of the column accessor in the related table.

NOTE: You need to explicitly quote '+columns' when defining the attribute. Not doing so causes Perl to incorrectly interpret +columns as a bareword with a unary plus operator before it.

include_columns

Value: \@columns

Deprecated. Acts as a synonym for "+columns" for backward compatibility.

select

Value: \@select_columns

Indicates which columns should be selected from the storage. You can use column names, or in the case of RDBMS back ends, function or stored procedure names:

$rs = $schema->resultset('Employee')->search(undef, {
  select => [
    'name',
    { count => 'employeeid' },
    { max => { length => 'name' }, -as => 'longest_name' }
  ]
});

# Equivalent SQL
SELECT name, COUNT( employeeid ), MAX( LENGTH( name ) ) AS longest_name FROM employee

NOTE: You will almost always need a corresponding "as" attribute when you use "select", to instruct DBIx::Class how to store the result of the column. Also note that the "as" attribute has nothing to do with the SQL-side 'AS' identifier aliasing. You can however alias a function, so you can use it in e.g. an ORDER BY clause. This is done via the -as select function attribute supplied as shown in the example above.

NOTE: You need to explicitly quote '+select'/'+as' when defining the attributes. Not doing so causes Perl to incorrectly interpret them as a bareword with a unary plus operator before it.

+select

Indicates additional columns to be selected from storage. Works the same as "select" but adds columns to the default selection, instead of specifying an explicit list.

+as

Indicates additional column names for those added via "+select". See "as".

as

Value: \@inflation_names

Indicates column names for object inflation. That is "as" indicates the slot name in which the column value will be stored within the Row object. The value will then be accessible via this identifier by the get_column method (or via the object accessor if one with the same name already exists) as shown below. The "as" attribute has nothing to do with the SQL-side AS. See "select" for details.

$rs = $schema->resultset('Employee')->search(undef, {
  select => [
    'name',
    { count => 'employeeid' },
    { max => { length => 'name' }, -as => 'longest_name' }
  ],
  as => [qw/
    name
    employee_count
    max_name_length
  /],
});

If the object against which the search is performed already has an accessor matching a column name specified in as, the value can be retrieved using the accessor as normal:

my $name = $employee->name();

If on the other hand an accessor does not exist in the object, you need to use get_column instead:

my $employee_count = $employee->get_column('employee_count');

You can create your own accessors if required - see DBIx::Class::Manual::Cookbook for details.

join

Value: ($rel_name | \@rel_names | \%rel_names)

Contains a list of relationships that should be joined for this query. For example:

# Get CDs by Nine Inch Nails
my $rs = $schema->resultset('CD')->search(
  { 'artist.name' => 'Nine Inch Nails' },
  { join => 'artist' }
);

Can also contain a hash reference to refer to the other relation's relations. For example:

package MyApp::Schema::Track;
use base qw/DBIx::Class/;
__PACKAGE__->table('track');
__PACKAGE__->add_columns(qw/trackid cd position title/);
__PACKAGE__->set_primary_key('trackid');
__PACKAGE__->belongs_to(cd => 'MyApp::Schema::CD');
1;

# In your application
my $rs = $schema->resultset('Artist')->search(
  { 'track.title' => 'Teardrop' },
  {
    join     => { cd => 'track' },
    order_by => 'artist.name',
  }
);

You need to use the relationship (not the table) name in conditions, because they are aliased as such. The current table is aliased as "me", so you need to use me.column_name in order to avoid ambiguity. For example:

# Get CDs from 1984 with a 'Foo' track
my $rs = $schema->resultset('CD')->search(
  {
    'me.year' => 1984,
    'tracks.name' => 'Foo'
  },
  { join => 'tracks' }
);

If the same join is supplied twice, it will be aliased to <rel>_2 (and similarly for a third time). For e.g.

my $rs = $schema->resultset('Artist')->search({
  'cds.title'   => 'Down to Earth',
  'cds_2.title' => 'Popular',
}, {
  join => [ qw/cds cds/ ],
});

will return a set of all artists that have both a cd with title 'Down to Earth' and a cd with title 'Popular'.

If you want to fetch related objects from other tables as well, see prefetch below.

For more help on using joins with search, see DBIx::Class::Manual::Joining.

prefetch

Value: ($rel_name | \@rel_names | \%rel_names)

Contains one or more relationships that should be fetched along with the main query (when they are accessed afterwards the data will already be available, without extra queries to the database). This is useful for when you know you will need the related objects, because it saves at least one query:

my $rs = $schema->resultset('Tag')->search(
  undef,
  {
    prefetch => {
      cd => 'artist'
    }
  }
);

The initial search results in SQL like the following:

SELECT tag.*, cd.*, artist.* FROM tag
JOIN cd ON tag.cd = cd.cdid
JOIN artist ON cd.artist = artist.artistid

DBIx::Class has no need to go back to the database when we access the cd or artist relationships, which saves us two SQL statements in this case.

Simple prefetches will be joined automatically, so there is no need for a join attribute in the above search.

"prefetch" can be used with the any of the relationship types and multiple prefetches can be specified together. Below is a more complex example that prefetches a CD's artist, its liner notes (if present), the cover image, the tracks on that cd, and the guests on those tracks.

# Assuming:
My::Schema::CD->belongs_to( artist      => 'My::Schema::Artist'     );
My::Schema::CD->might_have( liner_note  => 'My::Schema::LinerNotes' );
My::Schema::CD->has_one(    cover_image => 'My::Schema::Artwork'    );
My::Schema::CD->has_many(   tracks      => 'My::Schema::Track'      );

My::Schema::Artist->belongs_to( record_label => 'My::Schema::RecordLabel' );

My::Schema::Track->has_many( guests => 'My::Schema::Guest' );


my $rs = $schema->resultset('CD')->search(
  undef,
  {
    prefetch => [
      { artist => 'record_label'},  # belongs_to => belongs_to
      'liner_note',                 # might_have
      'cover_image',                # has_one
      { tracks => 'guests' },       # has_many => has_many
    ]
  }
);

This will produce SQL like the following:

SELECT cd.*, artist.*, record_label.*, liner_note.*, cover_image.*,
       tracks.*, guests.*
  FROM cd me
  JOIN artist artist
    ON artist.artistid = me.artistid
  JOIN record_label record_label
    ON record_label.labelid = artist.labelid
  LEFT JOIN track tracks
    ON tracks.cdid = me.cdid
  LEFT JOIN guest guests
    ON guests.trackid = track.trackid
  LEFT JOIN liner_notes liner_note
    ON liner_note.cdid = me.cdid
  JOIN cd_artwork cover_image
    ON cover_image.cdid = me.cdid
ORDER BY tracks.cd

Now the artist, record_label, liner_note, cover_image, tracks, and guests of the CD will all be available through the relationship accessors without the need for additional queries to the database.

However, there is one caveat to be observed: it can be dangerous to prefetch more than one has_many relationship on a given level. e.g.:

my $rs = $schema->resultset('CD')->search(
  undef,
  {
    prefetch => [
      'tracks',                         # has_many
      { cd_to_producer => 'producer' }, # has_many => belongs_to (i.e. m2m)
    ]
  }
);

In fact, DBIx::Class will emit the following warning:

Prefetching multiple has_many rels tracks and cd_to_producer at top
level will explode the number of row objects retrievable via ->next
or ->all. Use at your own risk.

The collapser currently can't identify duplicate tuples for multiple has_many relationships and as a result the second has_many relation could contain redundant objects.

Using "prefetch" with "join"

"prefetch" implies a "join" with the equivalent argument, and is properly merged with any existing "join" specification. So the following:

 my $rs = $schema->resultset('CD')->search(
  {'record_label.name' => 'Music Product Ltd.'},
  {
    join     => {artist => 'record_label'},
    prefetch => 'artist',
  }
);

... will work, searching on the record label's name, but only prefetching the artist.

Using "prefetch" with "select" / "+select" / "as" / "+as"

"prefetch" implies a "+select"/"+as" with the fields of the prefetched relations. So given:

 my $rs = $schema->resultset('CD')->search(
  undef,
  {
    select   => ['cd.title'],
    as       => ['cd_title'],
    prefetch => 'artist',
  }
);

The "select" becomes: 'cd.title', 'artist.*' and the "as" becomes: 'cd_title', 'artist.*'.

CAVEATS

Prefetch does a lot of deep magic. As such, it may not behave exactly as you might expect.

Prefetch uses the "cache" to populate the prefetched relationships. This may or may not be what you want.
If you specify a condition on a prefetched relationship, ONLY those rows that match the prefetched condition will be fetched into that relationship. This means that adding prefetch to a search() may alter what is returned by traversing a relationship. So, if you have Artist->has_many(CDs) and you do
```
my $artist_rs = $schema->resultset('Artist')->search({
    'cds.year' => 2008,
}, {
    join => 'cds',
});

my $count = $artist_rs->first->cds->count;

my $artist_rs_prefetch = $artist_rs->search( {}, { prefetch => 'cds' } );

my $prefetch_count = $artist_rs_prefetch->first->cds->count;

cmp_ok( $count, '==', $prefetch_count, "Counts should be the same" );
```
that cmp_ok() may or may not pass depending on the datasets involved. This behavior may or may not survive the 0.09 transition.

rows

Value: $rows

Specifies the maximum number of rows for direct retrieval or the number of rows per page if the page attribute or method is used.

offset

Value: $offset

Specifies the (zero-based) row number for the first row to be returned, or the of the first row of the first page if paging is used.

group_by

Value: \@columns

A arrayref of columns to group by. Can include columns of joined tables.

group_by => [qw/ column1 column2 ... /]

having

Value: $condition

HAVING is a select statement attribute that is applied between GROUP BY and ORDER BY. It is applied to the after the grouping calculations have been done.

having => { 'count_employee' => { '>=', 100 } }

or with an in-place function in which case literal SQL is required:

having => \[ 'count(employee) >= ?', [ count => 100 ] ]

distinct

Value: (0 | 1)

Set to 1 to group by all columns. If the resultset already has a group_by attribute, this setting is ignored and an appropriate warning is issued.

where

Adds to the WHERE clause.

# only return rows WHERE deleted IS NULL for all searches
__PACKAGE__->resultset_attributes({ where => { deleted => undef } }); )

Can be overridden by passing { where => undef } as an attribute to a resultset.

cache

Set to 1 to cache search results. This prevents extra SQL queries if you revisit rows in your ResultSet:

my $resultset = $schema->resultset('Artist')->search( undef, { cache => 1 } );

while( my $artist = $resultset->next ) {
  ... do stuff ...
}

$rs->first; # without cache, this would issue a query

By default, searches are not cached.

For more examples of using these attributes, see DBIx::Class::Manual::Cookbook.

for

Value: ( 'update' | 'shared' )

Set to 'update' for a SELECT ... FOR UPDATE or 'shared' for a SELECT ... FOR SHARED.

To install DBIx::Class, copy and paste the appropriate command in to your terminal.

cpanm

cpanm DBIx::Class

CPAN shell

perl -MCPAN -e shell
install DBIx::Class

For more information on module installation, please visit the detailed CPAN module installation guide.

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NAME

SYNOPSIS

DESCRIPTION

EXAMPLES

Chaining resultsets

Resolving conditions and attributes

Multiple queries

METHODS

new

search

CAVEAT

search_rs

search_literal

find

search_related

search_related_rs

cursor

single

get_column

search_like

slice

next

result_source

result_class

count

count_rs

count_literal

all

reset

first

update

CAVEAT

update_all

delete

delete_all

populate

pager

page

new_result

as_query

find_or_new

create

find_or_create

update_or_create

update_or_new

get_cache

set_cache

clear_cache

is_paged

is_ordered

related_resultset

current_source_alias

as_subselect_rs

throw_exception

ATTRIBUTES

order_by

columns

+columns

include_columns

select

+select

+as

as

join

prefetch

Using "prefetch" with "join"

Using "prefetch" with "select" / "+select" / "as" / "+as"

CAVEATS

page

rows

offset

group_by

having

distinct

where

cache

for

Module Install Instructions