2009/11/24 Randal L. Schwartz <mer...@stonehenge.com>:
>>>>>> "Dermot" == Dermot <paik...@googlemail.com> writes:
>
>
> ...
>
> Dermot> I guess the question is: Will the declaration of our %cache within a
> Dermot> function-orientated sub-routine render it always uninitialized?
>
> I believe what you are seeing is that %cache is per-child, so it has
> to compute it *once* for each child, not once for the server overall.
Actually I've made a bobo. This program doesn't run within modperl but
from the command-line. It updates a DB. But it worked really well. A
few print statements show that the hash is initialised once at the
first invocation of the get_cached_val_or_lookup().
package MyPack::Handlers;
our %cache;
...
..
sub get_cached_val_or_lookup {
my $val = shift;
return $cache{$val} ||= do {
print STDERR "Having to lookup value for $val as the hash key
didn't exist\n";
my $sql = qq(SELECT DISTINCT price_code, price_id FROM prices);
my $dbq = dbiQuery($sql);
if ($dbq->success && $dbq->rows) { # DBI sub-classed methods
while ( $dbq->fetch() ) {
my $code = ($dbq->row())[0];
$cache{$code} = ($dbq->row())[1];
}
return $cache{$val};
}
}
}
1;
One more question If I can. Chas pointed me to
http://perldesignpatterns.com/?PerlDesignPatterns some time ago. I
suspect that the above is a form of design pattern. Does it have a
name? Is there a reference to it at
http://perldesignpatterns.com/?PerlDesignPatterns
Thanx,
Dp.
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