com.datastax.dse.driver.api.core.cql.reactive

Interface ReactiveQueryMetadata

All Known Subinterfaces:

ContinuousReactiveResultSet, ReactiveResultSet

public interface ReactiveQueryMetadata

Interface implemented by all the reactive result set publishers provided by the driver, and notably by ReactiveResultSet.

Method Summary

Modifier and Type	Method and Description
org.reactivestreams.Publisher<? extends ColumnDefinitions>	getColumnDefinitions() Returns metadata about the columns contained in this result set.
org.reactivestreams.Publisher<? extends ExecutionInfo>	getExecutionInfos() Returns information about the execution of all requests that have been performed so far to assemble this result set.
org.reactivestreams.Publisher<Boolean>	wasApplied() If the query that produced this result was a conditional update, indicates whether it was successfully applied.

Method Detail

getColumnDefinitions

@NonNull
org.reactivestreams.Publisher<? extends ColumnDefinitions> getColumnDefinitions()

Returns metadata about the columns contained in this result set.

This publisher emits exactly one item as soon as the first response arrives, then completes. If the query execution fails within the first request-response cycle, then this publisher will fail with the same error; however if the error happens after the first response, then this publisher will be already completed and will not acknowledge that error in any way.

By default, publishers returned by this method do not support multiple subscriptions.

See Also:

ReactiveRow.getColumnDefinitions()

getExecutionInfos

@NonNull
org.reactivestreams.Publisher<? extends ExecutionInfo> getExecutionInfos()

Returns information about the execution of all requests that have been performed so far to assemble this result set.

If the query is not paged, this publisher will emit exactly one item as soon as the response arrives, then complete. If the query is paged, it will emit multiple items, one per page; then it will complete when the last page arrives. If the query execution fails, then this publisher will fail with the same error.

By default, publishers returned by this method do not support multiple subscriptions.

See Also:

ReactiveRow.getExecutionInfo()

wasApplied

@NonNull
org.reactivestreams.Publisher<Boolean> wasApplied()

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

This publisher emits exactly one item as soon as the first response arrives, then completes. If the query execution fails within the first request-response cycle, then this publisher will fail with the same error; however if the error happens after the first response, then this publisher will be already completed and will not acknowledge that error in any way.

By default, publishers returned by this method do not support multiple subscriptions.

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.

See Also:

ReactiveRow.wasApplied()