com.datastax.dse.driver.api.core.cql.continuous.ContinuousResultSet Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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* See the License for the specific language governing permissions and
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*/
package com.datastax.dse.driver.api.core.cql.continuous;
import com.datastax.oss.driver.api.core.cql.ExecutionInfo;
import com.datastax.oss.driver.api.core.cql.ResultSet;
import com.datastax.oss.driver.api.core.cql.Statement;
import edu.umd.cs.findbugs.annotations.NonNull;
import java.nio.ByteBuffer;
import java.util.List;
/**
* The result of a {@linkplain ContinuousSession#executeContinuously(Statement) synchronous
* continuous paging query}.
*
* It uses {@linkplain ContinuousAsyncResultSet asynchronous calls} internally, but blocks on the
* results in order to provide a synchronous API to its clients. If the query is paged, only the
* first page will be fetched initially, and iteration will trigger background fetches of the next
* pages when necessary.
*
*
Note that this object can only be iterated once: rows are "consumed" as they are read,
* subsequent calls to {@code iterator()} will return the same iterator instance.
*
*
Implementations of this type are not thread-safe. They can only be iterated by the
* thread that invoked {@code session.executeContinuously}.
*/
public interface ContinuousResultSet extends ResultSet {
/**
* Cancels the continuous query.
*
*
There might still be rows available in the current page after the cancellation; the
* iteration will only stop when such rows are fully iterated upon.
*
*
Also, there might be more pages available in the driver's local page cache after the
* cancellation; these extra pages will be discarded.
*
*
Therefore, if you plan to resume the iteration later, the correct procedure is as follows:
*
*
* - Cancel the operation by invoking this method;
*
- Keep iterating on this object until it doesn't return any more rows;
*
- Retrieve the paging state with {@link #getExecutionInfo()
* getExecutionInfo().getPagingState()};
*
- {@linkplain Statement#setPagingState(ByteBuffer) Re-inject the paging state} in the
* statement;
*
- Resume the operation by invoking {@link ContinuousSession#executeContinuously(Statement)
* executeContinuously} again.
*
*/
void cancel();
/**
* {@inheritDoc}
*
* Note: because the driver does not support query traces for continuous queries, {@link
* ExecutionInfo#getTracingId()} will always be {@code null}.
*/
@NonNull
@Override
default ExecutionInfo getExecutionInfo() {
List infos = getExecutionInfos();
return infos.get(infos.size() - 1);
}
}