IO::Lambda::DBI(3p)

NAME
IO::Lambda::DBI - asynchronous DBI

DESCRIPTION
The module implements asynchronous DBI proxy object, that remotes DBI calls using any given file handle, such as stream sockets, pipes, etc. All calls to DBI methods are implemented as method calls to the object, which return lambdas, that shall be subsequently called and awaited for completion.

SYNOPSIS
    use IO::Lambda qw(:all);
    use IO::Lambda::DBI;
    use IO::Lambda::Thread qw(new_thread);

    # use threads as a transport
    my ($thread, $socket) = new_thread( sub {
        IO::Lambda::Message::DBI-> new( shift )-> run;
    }, 1);

    my $dbi = IO::Lambda::DBI-> new($socket);

    # execute a query
    print lambda {
        context $dbi-> connect('DBI:mysql:database=mysql', '', '');
    tail {
        return "connect error:$_[0]" unless shift;
        context $dbi-> selectrow_array('SELECT 5 + ?', {}, 2);
    tail {
        my ($ok,$result) = @_;
        return "dbi error:$result" unless $ok;
        context $dbi-> disconnect;
    tail {
        return "select=$result";
    }}}}-> wait, "\n";

    # finalize
    $thread-> join;

IO::Lambda::DBI
All remoted methods return lambdas of type

   dbi_result :: () -> ( 1, @result | 0, $error )

where depending on the first returned item in the array, the other items are either DBI method results, or an error.

The class handles AUTOLOAD methods as proxy methods, so calls such as "$dbh-> selectrow_array" are perfectly legal.

new $class, $r, $w, %options
    See "new" in IO::Lambda::Message.

connect($dsn, $user, $auth, %attr) :: dbi_result
    Proxies "DBI::connect". In case of failure, depending on "RaiseError" flag, returns either "(0,$error)" or "(1,$error)".

disconnect :: dbi_result
    Proxies "DBI::disconnect".

call($method, @parameters) :: dbi_result
    Proxies "DBI::$method(@parameters)".

set_attr(%attr)
    Sets attributes on a DBI handle.

get_attr(@keys)
    Retrieves values for attribute keys from a DBI handle.

prepare($statement)
    Returns a new prepared statement object or an error string. All method calls on this object return lambda that also wait until remote methods are executed.

begin_group(), end_group()
    These two methods allow grouping of DBI calls. begin_group() affects a "IO::Lambda::DBI" object so that all calls to remoted methods are not stored in the queue (and, consequently, not executed one at a time), but are accumulated instead. end_group() ends such buffering, sends the message incapsulating all stored calls, and returns a lambda that executes when all stored calls are finished and replied to. The lambda returns results to all accumulated calls.

    Note: each stored call registers whether it is called in array or scalar context. The results are returned accordingly in a list, so the caller is responsible for parsing the results if some or all calls were made in the array context.

    Example:

        context
            $dbi-> begin_group,
            $dbi-> selectrow_arrayref("select * from a"),
            $dbi-> selectrow_arrayref("select * from b"),
            $dbi-> end_group;
        tail {
            return warn "error:$_[0]" unless shift;
            my ( $a, $b) = @_;
        }

IO::Lambda::Message::DBI
Descendant of "IO::Lambda::Message::Simple". Implements blocking, server side that does the actual calls to the DBI.

SEE ALSO
DBI, eg/dbi.pl.

AUTHOR
Dmitry Karasik, <dmitry@karasik.eu.org>.