NAME
Couchbase::Client::Iterator - Iterator for Couchbase GET requests
SYNOPSIS
my @keys = map { "A_Key_$_" } (0..1000);
my $iterator = $cbo->get_iterator(\@keys);
# Might want to check for error:
if ($iterator->error) {
die "Couldn't create iterator: " . $iterator->error->errstr();
}
while (my ($key,$ret) = $iterator->next) {
printf("I Got value %s for key %s\n", $ret->value, $key);
}DESCRIPTION
This package provides the iterator object, allowing a by-key iteration for multi-get requests.
This increases efficiency on the server-side by reducing packet size, while also reducing memory usage on the client side (so all responses do not need to be buffered before they are read).
In particular, if you are fetching a large number of keys (many of which may not exist), then you save a significant amount of memory involved in compiling the resultset.
Use of this iterator and its implementation was designed as a model for the more complex Couchbase::Couch iterator interface.
$cbo->get_iterator(@keys)
This creates a new iterator. See get_multi in Couchbbase::Client for the arguments to this function.
Instead of using a normal get_multi, it returns an iterator object which can be iterated over until all keys are exhausted.
This function always returns a Couchbase::Client::Iterator object.
If an error ocurred during the initial creation, it will be accessible via the error method.
$iter->next
When called in list context, returns a pair of ($key,$return) pairs, where $key is one of the keys requested, and $return is a Couchbase::Client::Return object.
When called in scalar context, it makes a best effort to return the number of items remaining to be fetched. This is probably not very useful, so don't call it in scalar context.
When there are no more items to fetch, a false value is returned.
$iter->error
Returns a Couchbase::Client::Return object if any error has ocurred while creating the iterator
$iter->remaining
Returns the amount of items remaining to be fetched
NOTES AND CAVEATS
Because the client uses a single socket for each server, mixing an iterator with other request types will at best reduce its effectiveness (all data will need to be buffered) and break things at worse. So don't do something like:
while (my ($k,$v) = $iterator->next) {
$cbo->store($k, "new_v");
}If you need such functionality, you should create a second Couchbase::Client object (thereby creating a second set of streams).