On Aug 5, 1:16 am, Bennett Haselton <[email protected]> wrote:
> It seems that with Cache::Memcached::Fast, if you use gets() on a key
> that doesn't exist, and use cas() to set the key value later, this
> fails, if the key didn't exist at the time you called gets() on it.
>
> The following code succeeds if $keyname is set to a key that already
> exists in memcached, however it fails (outputs "Update failed") if
> $keyname is set to something that didn't already exist:
>
> ****
> use Cache::Memcached::Fast;
> use strict;
>
> my $keyname = '20090804';
>
> # Configure the memcached server
>
> my $cache = new Cache::Memcached::Fast {
> 'servers' => [
> 'localhost:11211',
> ],
> };
>
> print "Existing value: " . $cache->get($keyname) . "\n";
>
> my $cas_val = $cache->gets($keyname);
>
> $$cas_val[1] = 'newval';
>
> if ($cache->cas($keyname, @$cas_val))
> {
> print "OK, value updated\n";}
>
> else
> {
> print "Update failed\n";}
>
> ****
>
> It seems counterintuitive to me that the update would fail if the key
> never existed in the first place. My understanding is you use gets
> and cas if what you want to do is retrieve a value, and then update
> the value only if the value hasn't been changed since you retrieved
> it. In the case of a nonexistent key, then the value hasn't
> "changed" since you retrieved it (it was empty before, and it still
> is), so the update should succeed.
>
> Is there a way to change this behavior? Otherwise, I'll just have to
> write code with two branches every time I want to update a value
> using gets() and cas() -- first, check if the key already exists (and
> if so, update it using gets() and cas()), otherwise, update it using
> get() and set() (because I can't get gets() and cas() to work on a
> non-pre-existing key).
>
> -Bennett
Can't you get the actual result code returned by memcache,
and if it is RES_NOTFOUND (IIRC) simply attempt an add() ?
Jared
