- All Superinterfaces:
public interface TupleMapFactory<Config>
- extends CascadingFactory<Config,Map<Tuple,Collection<Tuple>>>
Interface TupleMapFactory allows developers to plugin alternative implementations of a "tuple map"
used to back in memory "join" and "co-group" operations. Typically these implementations are
"spillable", in that to prevent using up all memory in the JVM, after some threshold is met or event
is triggered, values are persisted to disk.
Map classes returned must take a
Tuple as a key, and a
Collection of Tuples as
a value. Further,
Map.get(Object) must never return
null, but on the first call to get() on the map
an empty Collection must be created and stored.
Map.put(Object, Object) is never called on the map instance internally,
TupleCollectionFactory to create the underlying Tuple Collections would allow that aspect
to be pluggable as well.
If the Map implementation implements the
Spillable interface, it will receive a
instance that calls back to the appropriate logging mechanism for the platform. This instance should be passed
down to any child Spillable types, namely an implementation of
The default implementation for the Hadoop platform is the
which created a
SpillableTupleMap may be used as a base class.
- See Also:
static final String TUPLE_MAP_FACTORY
- See Also:
- Constant Field Values
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