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NAME |
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AnyEvent::DBI - asynchronous DBI access |
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SYNOPSIS |
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use AnyEvent::DBI; |
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my $cv = AnyEvent->condvar; |
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my $dbh = new AnyEvent::DBI "DBI:SQLite:dbname=test.db", "", ""; |
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$dbh->exec ("select * from test where num=?", 10, sub { |
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my ($rows, $rv) = @_; |
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print "@$_\n" |
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for @$rows; |
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$cv->broadcast; |
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}); |
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# asynchronously do sth. else here |
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|
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$cv->wait; |
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DESCRIPTION |
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This module is an AnyEvent user, you need to make sure that you use and |
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run a supported event loop. |
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This module implements asynchronous DBI access my forking or executing |
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separate "DBI-Server" processes and sending them requests. |
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It means that you can run DBI requests in parallel to other tasks. |
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The overhead for very simple statements ("select 0") is somewhere around |
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120% to 200% (dual/single core CPU) compared to an explicit |
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prepare_cached/execute/fetchrow_arrayref/finish combination. |
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METHODS |
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$dbh = new AnyEvent::DBI $database, $user, $pass, [key => value]... |
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Returns a database handle for the given database. Each database |
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handle has an associated server process that executes statements in |
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order. If you want to run more than one statement in parallel, you |
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need to create additional database handles. |
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The advantage of this approach is that transactions work as state is |
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preserved. |
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Example: |
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$dbh = new AnyEvent::DBI |
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"DBI:mysql:test;mysql_read_default_file=/root/.my.cnf", "", ""; |
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Additional key-value pairs can be used to adjust behaviour: |
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on_error => $callback->($dbh, $filename, $line, $fatal) |
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When an error occurs, then this callback will be invoked. On |
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entry, $@ is set to the error message. $filename and $line is |
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where the original request was submitted. |
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If this callback returns and this was a fatal error ($fatal is |
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true) then AnyEvent::DBI die's, otherwise it calls the original |
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request callback without any arguments. |
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If omitted, then "die" will be called on any errors, fatal or |
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not. |
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$dbh->exec ("statement", @args, $cb->($rows, $rv, ...)) |
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Executes the given SQL statement with placeholders replaced by |
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@args. The statement will be prepared and cached on the server side, |
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so using placeholders is compulsory. |
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The callback will be called with the result of "fetchall_arrayref" |
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as first argument (or "undef" if the statement wasn't a select |
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statement) and the return value of "execute" as second argument. |
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Additional arguments might get passed as well. |
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If an error occurs and the "on_error" callback returns, then no |
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arguments will be passed and $@ contains the error message. |
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SEE ALSO |
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AnyEvent, DBI. |
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AUTHOR |
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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