DBIx::Class::Storage(3)

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;
  try {
    $rs = $schema->txn_do($coderef);
  } catch {
    my $error = shift;
    # Transaction failed
    die "something terrible has happened!"
      if ($error =~ /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.

It does not perform an actual storage commit unless there's a DBIx::Class transaction currently in effect (i.e. you called "txn_begin").

  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.

  svp_begin
Arguments: $savepoint_name?

Created a new savepoint using the name provided as argument. If no name is provided, a random name will be used.

  svp_release
Arguments: $savepoint_name?

Release the savepoint provided as argument. If none is provided, release the savepoint created most recently. This will implicitly release all savepoints created after the one explicitly released as well.

  svp_rollback
Arguments: $savepoint_name?

Rollback to the savepoint provided as argument. If none is provided, rollback to the savepoint created most recently. This will implicitly release all savepoints created after the savepoint we rollback to.

  txn_scope_guard
An alternative way of transaction handling based on DBIx::Class::Storage::TxnScopeGuard:

 my $txn_guard = $storage->txn_scope_guard;

 $row->col1("val1");
 $row->update;

 $txn_guard->commit;

If an exception occurs, or the guard object otherwise leaves the scope before "$txn_guard->commit" is called, the transaction will be rolled back by an explicit "txn_rollback" call. In essence this is akin to using a "txn_begin"/"txn_commit" pair, without having to worry about calling "txn_rollback" at the right places. Note that since there is no defined code closure, there will be no retries and other magic upon database disconnection. If you need such functionality see "txn_do".

  sql_maker
Returns a "sql_maker" object - normally an object of class "DBIx::Class::SQLMaker".

  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 object (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.

  DBIC_TRACE_PROFILE
If "DBIC_TRACE_PROFILE" is set, DBIx::Class::Storage::Debug::PrettyPrint will be used to format the output from "DBIC_TRACE". The value it is set to is the "profile" that it will be used. If the value is a filename the file is read with Config::Any and the results are used as the configuration for tracing. See "new" in SQL::Abstract::Tree for what that structure should look like.

  DBIX_CLASS_STORAGE_DBI_DEBUG
Old name for DBIC_TRACE

SEE ALSO
DBIx::Class::Storage::DBI - reference storage implementation using SQL::Abstract and DBI.

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.