com.datastax.oss.driver.api.core

Interface AsyncPagingIterable<ElementT,SelfT extends AsyncPagingIterable<ElementT,SelfT>>

All Known Subinterfaces:

AsyncResultSet, ContinuousAsyncResultSet, MappedAsyncPagingIterable<ElementT>

public interface AsyncPagingIterable<ElementT,SelfT extends AsyncPagingIterable<ElementT,SelfT>>

An iterable of elements which are fetched asynchronously by the driver, possibly in multiple requests.

Method Summary

Modifier and Type	Method and Description
Iterable<ElementT>	currentPage() The elements in the current page.
CompletionStage<SelfT>	fetchNextPage() Fetch the next page of results asynchronously.
ColumnDefinitions	getColumnDefinitions() Metadata about the columns returned by the CQL request that was used to build this result.
ExecutionInfo	getExecutionInfo() Returns information about the execution of this page of results.
boolean	hasMorePages() Whether there are more pages of results.
default <TargetT> MappedAsyncPagingIterable<TargetT>	map(Function<? super ElementT,? extends TargetT> elementMapper) Creates a new instance by transforming each element of this iterable with the provided function.
default ElementT	one() Returns the next element, or null if the results are exhausted.
int	remaining() How many rows are left before the current page is exhausted.
boolean	wasApplied() If the query that produced this result was a CQL conditional update, indicate whether it was successfully applied.

Method Detail

getColumnDefinitions

@NonNull
ColumnDefinitions getColumnDefinitions()

Metadata about the columns returned by the CQL request that was used to build this result.

getExecutionInfo

@NonNull
ExecutionInfo getExecutionInfo()

Returns information about the execution of this page of results.

remaining

int remaining()

How many rows are left before the current page is exhausted.

currentPage

@NonNull
Iterable<ElementT> currentPage()

The elements in the current page. To keep iterating beyond that, use hasMorePages() and fetchNextPage().

Note that this method always returns the same object, and that that object can only be iterated once: elements are "consumed" as they are read.

one

@Nullable
default ElementT one()

Returns the next element, or null if the results are exhausted.

This is convenient for queries that are known to return exactly one element, for example count queries.

hasMorePages

boolean hasMorePages()

Whether there are more pages of results. If so, call fetchNextPage() to fetch the next one asynchronously.

fetchNextPage

@NonNull
CompletionStage<SelfT> fetchNextPage()
                                       throws IllegalStateException

Fetch the next page of results asynchronously.

Throws:

IllegalStateException - if there are no more pages. Use hasMorePages() to check if you can call this method.

wasApplied

boolean wasApplied()

If the query that produced this result was a CQL conditional update, indicate whether it was successfully applied.

For consistency, this method always returns true for non-conditional queries (although there is no reason to call the method in that case). This is also the case for conditional DDL statements (CREATE KEYSPACE... IF NOT EXISTS, CREATE TABLE... IF NOT EXISTS), for which Cassandra doesn't return an [applied] column.

Note that, for versions of Cassandra strictly lower than 2.1.0-rc2, a server-side bug (CASSANDRA-7337) causes this method to always return true for batches containing conditional queries.

map

default <TargetT> MappedAsyncPagingIterable<TargetT> map(Function<? super ElementT,? extends TargetT> elementMapper)

Creates a new instance by transforming each element of this iterable with the provided function.

Note that both instances share the same underlying data: consuming elements from the transformed iterable will also consume them from this object, and vice-versa.