herddb.core.PageReplacementPolicy Maven / Gradle / Ivy
/*
Licensed to Diennea S.r.l. under one
or more contributor license agreements. See the NOTICE file
distributed with this work for additional information
regarding copyright ownership. Diennea S.r.l. licenses this file
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, 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 herddb.core;
import java.util.Collection;
/**
* Cache replacement policy for memory pagination.
*
*
* A {@link PageReplacementPolicy} will not load or unload memory pages but will keep track of their usage and
* instruct the system about which page need to be replaced.
*
*
* @author diego.salvi
*/
public interface PageReplacementPolicy {
/**
* Track a page cache hit.
*
* @param page for which track an hit
*/
void pageHit(Page page);
/**
* Add a new {@code Page} to memory.
*
* Adding a new page could force an older page to be unloaded
*
*
* @param page page to be added
* @return selected page to be unloaded or {@code null}
*/
Page.Metadata add(Page page);
/**
* Remove a {@code Page} from memory.
*
* @param page page to be removed.
* @return {@code true} if the memory really contained the given page
*/
boolean remove(Page page);
/**
* Remove many {@code Page Pages} from memory.
*
* This method is logically equivalent to multiple {@link #remove(Page)} invocations but is expected
* to be more efficient.
*
*
* @param pages pages to be removed.
*/
> void remove(Collection
pages);
/**
* Returns the current number of {@link Page Pages} memorized.
*
* @return current number of Pages
*/
int size();
/**
* Returns the maximum number of {@link Page Pages} memorizable.
*
* @return maximum number of Pages
*/
int capacity();
/**
* Clear any memorized data.
*/
void clear();
}