DBIx::Class::Storage(3p)

NAME
DBIx::Class::Storage - Generic Storage Handler

DESCRIPTION
A base implementation of common Storage methods. For specific information about DBI-based storage, see DBIx::Class::Storage::DBI.

METHODS

  new
Arguments: $schema

Instantiates the Storage object.

  set_schema
Used to reset the schema class or object which owns this storage object, such as during "clone" in DBIx::Class::Schema.

  connected
Returns true if we have an open storage connection, false if it is not (yet) open.

  disconnect
Closes any open storage connection unconditionally.

  ensure_connected
Initiate a connection to the storage if one isn't already open.

  throw_exception
Throws an exception - croaks.

  txn_do

Arguments: $coderef, @coderef_args?
Return Value: The return value of $coderef

Executes $coderef with (optional) arguments @coderef_args atomically, returning its result (if any). If an exception is caught, a rollback is issued and the exception is rethrown. If the rollback fails, (i.e. throws an exception) an exception is thrown that includes a "Rollback failed" message.

For example,

  my $author_rs = $schema->resultset('Author')->find(1);
  my @titles = qw/Night Day It/;

  my $coderef = sub {
    # If any one of these fails, the entire transaction fails
    $author_rs->create_related('books', {
      title => $_
    }) foreach (@titles);

    return $author->books;
  };

  my $rs;
  eval {
    $rs = $schema->txn_do($coderef);
  };

  if ($@) {                                  # Transaction failed
    die "something terrible has happened!"   #
      if ($@ =~ /Rollback failed/);          # Rollback failed

    deal_with_failed_transaction();
  }

In a nested transaction (calling txn_do() from within a txn_do() coderef) only the outermost transaction will issue a "txn_commit", and txn_do() can be called in void, scalar and list context and it will behave as expected.

Please note that all of the code in your coderef, including non-DBIx::Class code, is part of a transaction. This transaction may fail out halfway, or it may get partially double-executed (in the case that our DB connection failed halfway through the transaction, in which case we reconnect and restart the txn). Therefore it is best that any side-effects in your coderef are idempotent (that is, can be re-executed multiple times and get the same result), and that you check up on your side-effects in the case of transaction failure.

  txn_begin
Starts a transaction.

See the preferred "txn_do" method, which allows for an entire code block to be executed transactionally.

  txn_commit
Issues a commit of the current transaction.

  txn_rollback
Issues a rollback of the current transaction. A nested rollback will throw a DBIx::Class::Storage::NESTED_ROLLBACK_EXCEPTION exception, which allows the rollback to propagate to the outermost transaction.

  sql_maker
Returns a "sql_maker" object - normally an object of class "DBIC::SQL::Abstract".

  debug
Causes trace information to be emitted on the "debugobj" object. (or "STDERR" if "debugobj" has not specifically been set).

This is the equivalent to setting "DBIC_TRACE" in your shell environment.

  debugfh
Set or retrieve the filehandle used for trace/debug output. This should be an IO::Handle compatible ojbect (only the "print" method is used. Initially set to be STDERR - although see information on the DBIC_TRACE environment variable.

  debugobj
Sets or retrieves the object used for metric collection. Defaults to an instance of DBIx::Class::Storage::Statistics that is compatible with the original method of using a coderef as a callback. See the aforementioned Statistics class for more information.

  debugcb
Sets a callback to be executed each time a statement is run; takes a sub reference. Callback is executed as $sub->($op, $info) where $op is SELECT/INSERT/UPDATE/DELETE and $info is what would normally be printed.

See debugobj for a better way.

  cursor_class
The cursor class for this Storage object.

  deploy
Deploy the tables to storage (CREATE TABLE and friends in a SQL-based Storage class). This would normally be called through "deploy" in DBIx::Class::Schema.

  connect_info
The arguments of "connect_info" are always a single array reference, and are Storage-handler specific.

This is normally accessed via "connection" in DBIx::Class::Schema, which encapsulates its argument list in an arrayref before calling "connect_info" here.

  select
Handle a select statement.

  insert
Handle an insert statement.

  update
Handle an update statement.

  delete
Handle a delete statement.

  select_single
Performs a select, fetch and return of data - handles a single row only.

  columns_info_for
Returns metadata for the given source's columns. This is *deprecated*, and will be removed before 1.0. You should be specifying the metadata yourself if you need it.

ENVIRONMENT VARIABLES

  DBIC_TRACE
If "DBIC_TRACE" is set then trace information is produced (as when the debug method is set).

If the value is of the form "1=/path/name" then the trace output is written to the file "/path/name".

This environment variable is checked when the storage object is first created (when you call connect on your schema). So, run-time changes to this environment variable will not take effect unless you also re-connect on your schema.

  DBIX_CLASS_STORAGE_DBI_DEBUG
Old name for DBIC_TRACE

AUTHORS
Matt S. Trout <mst@shadowcatsystems.co.uk>

Andy Grundman <andy@hybridized.org>

LICENSE
You may distribute this code under the same terms as Perl itself.