public class Result<T> extends Object implements PagingIterable<Result<T>,T>
| Modifier and Type | Method and Description |
|---|---|
List<T> |
all()
Returns all the remaining rows in this result set as a list.
|
ListenableFuture<Result<T>> |
fetchMoreResults()
Force fetching the next page of results for this result set, if any.
|
List<ExecutionInfo> |
getAllExecutionInfo()
Return the execution information for all queries made to retrieve this
result set.
|
int |
getAvailableWithoutFetching()
The number of rows that can be retrieved from this result set without
blocking to fetch.
|
ExecutionInfo |
getExecutionInfo()
Returns information on the execution of the last query made for this result set.
|
boolean |
isExhausted()
Returns whether this result set has more results.
|
boolean |
isFullyFetched()
Whether all results from this result set have been fetched from the
database.
|
Iterator<T> |
iterator()
Returns an iterator over the rows contained in this result set.
|
T |
one()
Returns the next result from this result set.
|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitforEach, spliteratorpublic boolean isExhausted()
PagingIterableisExhausted in interface PagingIterable<Result<T>,T>public T one()
PagingIterableone in interface PagingIterable<Result<T>,T>public List<T> all()
PagingIterable
Note that, contrary to PagingIterable.iterator() or successive calls to
PagingIterable.one(), this method forces fetching the full content of the result set
at once, holding it all in memory in particular. It is thus recommended
to prefer iterations through PagingIterable.iterator() when possible, especially
if the result set can be big.
all in interface PagingIterable<Result<T>,T>public Iterator<T> iterator()
PagingIterable
The Iterator.next() method is equivalent to calling PagingIterable.one().
So this iterator will consume results 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.
public ExecutionInfo getExecutionInfo()
PagingIterable
Note that in most cases, a result set is fetched with only one query, but large
result sets can be paged and thus be retrieved by multiple queries. In that
case this method return the ExecutionInfo for the last query
performed. To retrieve the information for all queries, use PagingIterable.getAllExecutionInfo().
The returned object includes basic information such as the queried hosts, but also the Cassandra query trace if tracing was enabled for the query.
getExecutionInfo in interface PagingIterable<Result<T>,T>public List<ExecutionInfo> getAllExecutionInfo()
PagingIterable
Unless the result set is large enough to get paged underneath, the returned
list will be singleton. If paging has been used however, the returned list
contains the ExecutionInfo objects for all the queries done to obtain this
result set (at the time of the call) in the order those queries were made.
getAllExecutionInfo in interface PagingIterable<Result<T>,T>public ListenableFuture<Result<T>> fetchMoreResults()
PagingIterable
This method is entirely optional. It will be called automatically while
the result set is consumed (through PagingIterable.one(), PagingIterable.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 results. This can allow to prefetch results before they are strictly needed. For instance, if you want to prefetch the next page of results as soon as there is less than 100 rows readily available in this result set, you can do:
ResultSet rs = session.execute(...);
Iterator<Row> iter = rs.iterator();
while (iter.hasNext()) {
if (rs.getAvailableWithoutFetching() == 100 && !rs.isFullyFetched())
rs.fetchMoreResults();
Row row = iter.next()
... process the row ...
}
This method is not blocking, so in the example above, the call to fetchMoreResults will not block the processing of the 100 currently available
rows (but iter.hasNext() will block once those rows have been processed
until the fetch query returns, if it hasn't yet).
Only one page of results (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 2nd call will simply return a future on the currently in progress query.
fetchMoreResults in interface PagingIterable<Result<T>,T>isFullyFetched() == true),
then the returned future will return immediately but not particular error will be
thrown (you should thus call PagingIterable.isFullyFetched() to know if calling this
method can be of any use}).public boolean isFullyFetched()
PagingIterable
Note that if isFullyFetched(), then PagingIterable.getAvailableWithoutFetching()
will return how many rows remain in the result set before exhaustion. But
please note that !isFullyFetched() never guarantees that the result set
is not exhausted (you should call PagingIterable.isExhausted() to verify it).
isFullyFetched in interface PagingIterable<Result<T>,T>public int getAvailableWithoutFetching()
PagingIterablegetAvailableWithoutFetching in interface PagingIterable<Result<T>,T>PagingIterable.isFullyFetched(), this is the total number of rows remaining
in this result set (after which the result set will be exhausted).Copyright © 2012–2018. All rights reserved.