NAME

Class::ReluctantORM::Manual::Monitors - Inspecting SQL Activity

OVERVIEW

One of the most frustrating tasks when working with an ORM in a production environment is tracing and optimizing the SQL that is generated. CRO eases this pain somewhat by providing monitors - objects that you can configure to watch for and report on the status of SQL generation. You can even abort a query if it exceeds certain parameters. CRO comes with a useful basic toolkit of 8 Monitors, to assist in tracing and optimizing queries. It's also easy to create new monitors of your own design, which can execute arbitrary Perl.

INSTALLING MONITORS

We'll first work with Class::ReluctantORM::Monitor::Dump, which simply dumps out various information to STDERR as queries execute.

use Class::ReluctantORM::Monitor::Dump;

# The 'all' flag says to dump everything, all the time
my $mon = Class::ReluctantORM::Monitor::Dump->new(all => 1);

# To monitor just queries on Ship objects:
Ship->

Dump can also send its output to a log file of your choice, and you can also tone down the avalanche of output. See Class::ReluctantORM::Monitor::Dump.

Now run some queries. You'll see output like this:

# In code
$ship->insert();

# On STDERR, gobs of info

MONITOR EVENTS

As a query makes its journey from SQL object to rendered SQL string, through execution, several events occur which a Monitor may choose to respond to. You can pass these as flags under the 'when' option to the Monitor's new().

render_begin

Notifies the monitoring system that the driver has begun work to render the given SQL object.

render_transform

Notifies the monitoring system that the driver has finished transforming the SQL object.

render_finish

Notifies the monitoring system that the driver has finished rendering the SQL object.

execute_begin

Notifies the monitoring system that the driver is about to perform a DBI execute.

execute_finish

Notifies the monitoring system that the driver has returned from performing a DBI execute.

fetch_row

Notifies the monitoring system that the driver has returned from performing a DBI fetchrow.

finish

Notifies the monitoring system that the driver has finished the query (called $sth->finish).

MONITORS INCLUDED WITH CRO

Dump

Dumps the query structures to the log.

QueryCounter

Counts the number of statements executed.

ColumnCounter

Counts the number of columns returned by a query.

JoinCounter

Counts the number of JOINs in the query.

QuerySize

Monitors the total size, in bytes, of the data returned by a query.

RowCounter

Monitors the number of rows returned by the query.

RowSize

Monitors the size, in bytes, of each individual row.

Timer

Tracks execution time of each query.

CREATING YOUR OWN MONITORS

To create a Monitor, simply inherit from Class::ReluctantORM. Then implement any of the notify_* methods you see fit.

AUTHOR

Clinton Wolfe clwolfe@cpan.org March 2010