/*
* Licensed 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,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.facebook.presto.operator;
import com.facebook.presto.spi.Page;
import com.facebook.presto.spi.type.Type;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import java.util.List;
public interface Operator
extends AutoCloseable
{
ListenableFuture<?> NOT_BLOCKED = Futures.immediateFuture(null);
OperatorContext getOperatorContext();
/**
* Gets the column types of pages produced by this operator.
*/
List<Type> getTypes();
/**
* Notifies the operator that no more pages will be added and the
* operator should finish processing and flush results. This method
* will not be called if the Task is already failed or canceled.
*/
void finish();
/**
* Is this operator completely finished processing and no more
* output pages will be produced.
*/
boolean isFinished();
/**
* Returns a future that will be completed when the operator becomes
* unblocked. If the operator is not blocked, this method should return
* {@code NOT_BLOCKED}.
*/
default ListenableFuture<?> isBlocked()
{
return NOT_BLOCKED;
}
/**
* Returns true if and only if this operator can accept an input page.
*/
boolean needsInput();
/**
* Adds an input page to the operator. This method will only be called if
* {@code needsInput()} returns true.
*/
void addInput(Page page);
/**
* Gets an output page from the operator. If no output data is currently
* available, return null.
*/
Page getOutput();
/**
* This method will always be called before releasing the Operator reference.
*/
@Override
default void close()
throws Exception
{
}
}