com.datastax.driver.core
Class ResultSet

java.lang.Object
  com.datastax.driver.core.ResultSet

All Implemented Interfaces:

Iterable<Row>

public class ResultSet
extends Object
implements Iterable<Row>

The result of a query. Note that this class is not thread-safe.

Method Summary

List<Row>	all() Returns all the remaining rows in this ResultSet as a list.
com.google.common.util.concurrent.ListenableFuture<Void>	fetchMoreResults() Force the fetching the next page of results for this result set, if any.
List<ExecutionInfo>	getAllExecutionInfo() Return the execution informations for all queries made to retrieve this ResultSet.
int	getAvailableWithoutFetching() The number of rows that can be retrieved from this result set without blocking to fetch.
ColumnDefinitions	getColumnDefinitions() Returns the columns returned in this ResultSet.
ExecutionInfo	getExecutionInfo() Returns information on the execution of the last query made for this ResultSet.
boolean	isExhausted() Returns whether this ResultSet has more results.
boolean	isFullyFetched() Whether all results from this result set has been fetched from the database.
Iterator<Row>	iterator() Returns an iterator over the rows contained in this ResultSet.
Row	one() Returns the the next result from this ResultSet.
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

getColumnDefinitions

public ColumnDefinitions getColumnDefinitions()

Returns the columns returned in this ResultSet.

Returns:

the columns returned in this ResultSet.

isExhausted

public boolean isExhausted()

Returns whether this ResultSet has more results.

Returns:

whether this ResultSet has more results.

one

public Row one()

Returns the the next result from this ResultSet.

Returns:

the next row in this resultSet or null if this ResultSet is exhausted.

all

public List<Row> all()

Returns all the remaining rows in this ResultSet as a list.

Returns:

a list containing the remaining results of this ResultSet. The returned list is empty if and only the ResultSet is exhausted.

iterator

public Iterator<Row> iterator()

Returns an iterator over the rows contained in this ResultSet. The Iterator.next() method is equivalent to calling one(). So this iterator will consume results from this ResultSet and after a full iteration, the ResultSet will be empty. The returned iterator does not support the Iterator.remove() method.

Specified by:

iterator in interface Iterable<Row>

Returns:

an iterator that will consume and return the remaining rows of this ResultSet.

getAvailableWithoutFetching

public int getAvailableWithoutFetching()

The number of rows that can be retrieved from this result set without blocking to fetch.

Returns:

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

isFullyFetched

public boolean isFullyFetched()

Whether all results from this result set has been fetched from the database.

Note that if isFullyFetched(), then getAvailableWithoutFetching() will return how much rows remains in the result set before exhaustion. But please note that !isFullyFetched() never guarantees that the result set is not exhausted (you should call isExhausted() to make sure of it).

Returns:

whether all results have been fetched.

fetchMoreResults

public com.google.common.util.concurrent.ListenableFuture<Void> fetchMoreResults()

Force the fetching the next page of results for this result set, if any.

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 stricly 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.

Returns:

a future on the completion of fetching the next page of results. If the result set is already fully retrieved (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).

getExecutionInfo

public ExecutionInfo getExecutionInfo()

Returns information on the execution of the last query made for this ResultSet.

Note that in most cases, a ResultSet is fetched with only one query, but large result sets can be paged and thus be retrieved by multiple queries. If that is the case, that method return that ExecutionInfo for the last query performed. To retrieve the informations 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.

Returns:

the execution info for the last query made for this ResultSet.

getAllExecutionInfo

public List<ExecutionInfo> getAllExecutionInfo()

Return the execution informations for all queries made to retrieve this ResultSet.

Unless the ResultSet 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 for all the queries done to obtain this ResultSet (at the time of the call) in the order those queries were made.

Returns:

a list of the execution info for all the queries made for this ResultSet.

toString

public String toString()

Overrides:

toString in class Object