comment on

Is there an easy way to override DBI::prepare or 'execute' in such a way that I can add some logging to give a stack trace (Carp::cluck) showing where every database query in a large body of code was called from, as it runs?

Assuming that you control the code that's doing the prepare(), a simple approach is to wrap the object that prepare() hands back. Something like:

    my $sth = $dbh->prepare("SELECT ... WHERE ... ? ...");
    $sth = Statement->wrap($sth, "Label");
    ...
    $sth->execute(@args);
[download]

The wrapping class looks something like:

    package Statement;

    sub wrap {
        my($pkg, $sth, $label) = @_;
        bless [ $sth, $label ], $pkg;
    }

    sub execute {
        my $self = shift;
        # tracing, timing code here. E.g.,
        log($self->[1] . " is about to execute");
        my $rv = $self->[0]->execute(@args);
        # timing, logging code here
    }

    sub finish {
        my $self = shift;
        $self->[0]->finish();
    }

    1;
[download]

You'll probably find that you need to wrap some additional methods.

The label helps track the statement and makes the logs more readable, and could include the text of the query.

In reply to Re: How to report call stack for DBI queries by dws
in thread How to report call stack for DBI queries by mp

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