You can override fetchall_arrayref method.

Just create dbilimit.pl

use strict;
package DBI;

my $fetchall_arrayref;
our $ROWS_LIMIT;

INIT {
    $ROWS_LIMIT = 10;
    $fetchall_arrayref = \&fetchall_arrayref;
}

no warnings;

sub fetchall_arrayref {
    my ($sth, $slice, $max_rows) = @_;

    $max_rows = $ROWS_LIMIT
      unless defined $max_rows;

    $fetchall_arrayref->($sth, $slice, $max_rows);
}

1;
[download]

P.S. the code is not tested so it may have some bugs

This what I was looking for! I didn't want to have to re-write every instance of a fetchall_arrayref or hashref in the code to a while fetch loop, that would have chaned the logic pf the program. Overridding the methods in this manner is much more concise and easier. Thank you, it did the job.

I may do that if I have too, but I like to keep the structure of the program intact if possible. I am debugging it in a visual debugger, and I want to see the results of the call, just not ALL the results. I am assuming then that the answer is no to a DBI specific method that limits the number of rows returned?

There in fact are method(s) that limit the number of results you get. They're called fetchrow_*(). They limit the number of results to one row so you can control however many you actually obtain. Straight out of the DBI documentation:

$sth = $dbh->prepare("SELECT foo, bar FROM table WHERE baz=?");

$sth->execute( $baz );

while ( @row = $sth->fetchrow_array ) {
    print "@row\n";
}
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Now you can transform this a little to suit your needs like merlyn was talking about:

my $LIMIT = 30;

my $sth = $dbh->prepare("SELECT foo, bar FROM table WHERE baz=?");
$sth->execute( $baz );

my ( @rows, @row );
for ( 1 .. $LIMIT ) {
    last unless ( @row = $sth->fetchrow_array );
    push @rows, [ @row ];
}

#do stuff with @rows
[download]

This code is untested but you get the general idea. There are other types of fetchrow_*() methods that you can take a look at. Read the DBI documentation.

Update: You can also take a look at the fetchall_arrayref() method which appears to take a $max_rows parameter.

Zenon Zabinski | zdog | zdog@perlmonk.org