Re: to prepare_cached or not?

On Thu, 14 Jun 2007, Greg Sabino Mullane wrote:

>> I have a bunch of queries which are not extremely performance sensitive.
>> What is the trade-off between prepare and prepare_cached? Is
>> prepare_cached basically free and I should use it all the time? Or is
>> there a significant memory cost and I should only use it for the most
>> time-critical queries?
>
> No significant memory or computation cost. It's a fairly cheap optimization.
> It's probably fine to use it all you want. Personally, I rarely use it myself,
> as my apps prepare things only once and keep pretty good track of what's
> already been prepared or not.



That depends, I can think of some instances were you would not want to use it:


for (1..100_000_000) {
     eval {
         my $sth = $dbh->prepare_cached(q{
             INSERT INTO mytable (number) VALUES ($_);
         });
         $sth->excute();
     }; if (my $e = $@) {
         die "Hmm there was an error... Did you forget to create mytable? $e";
     }
}


Or in general, any time you have something that will generate a large set of 
different statements....


-r