Modifier and Type | Method and Description |
---|---|
List<T> |
all()
Returns all the remaining rows in this result set as a list.
|
ListenableFuture<S> |
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.
|
forEach, spliterator
boolean isExhausted()
boolean isFullyFetched()
Note that if isFullyFetched()
, then 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 exhausted (you should call isExhausted()
to verify it).
int getAvailableWithoutFetching()
isFullyFetched()
,
this is the total number of rows remaining in this result set (after which the result set
will be exhausted).ListenableFuture<S> fetchMoreResults()
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 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.
isFullyFetched() == true
), then the returned future will
return immediately but not particular error will be thrown (you should thus call isFullyFetched()
to know if calling this method can be of any use}).T one()
List<T> all()
Note that, contrary to iterator()
or successive calls to 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 iterator()
when
possible, especially if the result set can be big.
Iterator<T> iterator()
The Iterator.next()
method is equivalent to calling 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.
ExecutionInfo getExecutionInfo()
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 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.
List<ExecutionInfo> getAllExecutionInfo()
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.
Copyright © 2012–2019. All rights reserved.