com.aquenos.cassandra.pvarchiver.common

Interface ObjectResultSet<V>

Type Parameters:

V - type of the object contained in the result set.

All Superinterfaces:

Iterable<V>

All Known Implementing Classes:

AbstractObjectResultSet, SimpleObjectResultSet

public interface ObjectResultSet<V>
extends Iterable<V>

Set of objects that represent the result of a query. This class closely resembles Cassandra's ResultSet. Basically, it provides the same methods but deals with typed objects instead of CQL rows.

This design is intended to make it very easy to wrap a ResultSet in a ObjectResultSet while retaining the possibility to implement a ObjectResultSet that is not based on a ResultSet.

Implementations of this interface have to be expected to be not thread safe.

Author:

Sebastian Marsching

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	ObjectResultSet.ObjectResultSetIterator<V> Simple implementation of an iterator that consumes a object result-set.

Method Summary

Modifier and Type	Method and Description
List<V>	all() Returns all remaining objects in this object result-set as a list.
ListenableFuture<Void>	fetchMoreResults() Forces fetching the next page of object for this object result-set.
int	getAvailableWithoutFetching() Returns the number of objects that can be retrieved from this object result-set without blocking to fetch.
boolean	isExhausted() Tells whether this object result-set has more objects.
boolean	isFullyFetched() Tells whether all objects from this object result set have been fetched from the database.
Iterator<V>	iterator() Returns an iterator over the objects contained in this object result-set.
V	one() Returns the next object from this object result-set.

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Method Detail

all

List<V> all()

Returns all remaining objects in this object result-set as a list.

Calls to this method will block until all objects have been retrieved from the database.

Note that, contrary to iterator() or successive calls to one(), this method forces fetching the full content of the object result-set at once, holding it all in memory in particular. It is thus recommended to prefer iterations through iterator() when possible, especially if the result set can be big.

Returns:

list containing the remaining objects of this object result set. The returned list is empty if and only this result set is exhausted. This result set will be exhausted after a call to this method.

fetchMoreResults

ListenableFuture<Void> fetchMoreResults()

Forces fetching the next page of object for this object result-set.

The use of this method is entirely optional. It will be called automatically while the result set is consumed (through one(), all() or iteration) when needed (i.e. when getAvailableWithoutFetching() == 0 and isFullyFetched() == false).

You can however call this method manually to force the fetching of the next page of objects. This can allow to prefetch objects before they are strictly needed.

This method is not blocking. However, hasNext() on the iterator returned by iterator() or calling one() will block until the fetch query returns if all objects that have been fetched previously have already been returned.

Only one page of objects (for a given result set) can be fetched at any given time. If this method is called twice and the query triggered by the first call has not returned yet when the second one is performed, then the second call will simply return a future on the currently in progress query.

Returns:

future on the completion of fetching the next page of objects. If the result set is already fully retrieved ( isFullyFetched() == true), then the returned future will return immediately (you should thus call isFullyFetched() to know if calling this method can be of any use}).

getAvailableWithoutFetching

int getAvailableWithoutFetching()

Returns the number of objects that can be retrieved from this object result-set without blocking to fetch.

Returns:

number of objects readily available in this object result-set. If isFullyFetched(), this is the total number of objects remaining in this result set (after which the result set will be exhausted).

isExhausted

boolean isExhausted()

Tells whether this object result-set has more objects.

Calls to this method may block if getAvailableWithoutFetching() == 0 and isFullyFetched() == false.

Returns:

true if this object result-set is exhausted ( one() == null), false if there are objects left in this result set.

isFullyFetched

boolean isFullyFetched()

Tells whether all objects from this object result set have been fetched from the database.

Note that if this method returns true, then getAvailableWithoutFetching() will return how many objects remain in the result set before exhaustion. However, if this method returns false, this does not guarantee that the result set is not exhausted (you should call isExhausted() to verify it).

Returns:

true if all objects have been fetched, false if there might be more objects that have not been loaded from the database yet.

iterator

Iterator<V> iterator()

Returns an iterator over the objects contained in this object result-set.

Calls to the Iterator.hasNext() method may block if getAvailableWithoutFetching() == 0 and isFullyFetched() == false.

The Iterator.next() method is equivalent to calling one(). So this iterator will consume objects from this result set and after a full iteration, the result set will be empty.

The returned iterator does not support the Iterator.remove() method.

Specified by:

iterator in interface Iterable<V>

Returns:

iterator that will consume and return the remaining objects of this object result-set.

one

V one()

Returns the next object from this object result-set.

Calls to this method may block if getAvailableWithoutFetching() == 0 and isFullyFetched() == false.

Returns:

next object in this object result-set or null if this result set is exhausted.