org.neo4j.io.pagecache

Interface PageCache

All Superinterfaces:

AutoCloseable

public interface PageCache
extends AutoCloseable

A page caching mechanism that allows caching multiple files and accessing their data in pages via a re-usable cursor. This interface does not specify the cache eviction and allocation behavior, it may be backed by implementations that map entire files into RAM, or implementations with smart eviction strategies, trying to keep "hot" pages in RAM.

Method Summary

Methods

Modifier and Type	Method and Description
void	close() Flush all dirty pages and close the page cache.
void	flushAndForce() Flush all dirty pages
PagedFile	map(File file, int pageSize, OpenOption... openOptions) Ask for a handle to a paged file, backed by this page cache.
int	maxCachedPages() The max number of cached pages.
int	pageSize() The size in bytes of the pages managed by this cache.

Method Detail

map

PagedFile map(File file,
            int pageSize,
            OpenOption... openOptions)
              throws IOException

Ask for a handle to a paged file, backed by this page cache. Note that this currently asks for the pageSize to use, which is an artifact or records being of varying size in the stores. This should be consolidated to use a standard page size for the whole cache, with records aligning on those page boundaries.

Parameters:

file - The file to map.

pageSize - The file page size to use for this mapping. If the file is already mapped with a different page size, an exception will be thrown.

openOptions - The set of open options to use for mapping this file. The StandardOpenOption.READ and StandardOpenOption.WRITE options always implicitly specified. The StandardOpenOption.CREATE open option will create the given file if it does not already exist, and the StandardOpenOption.TRUNCATE_EXISTING will truncate any existing file iff it has not already been mapped. All other options are either silently ignored, or will cause an exception to be thrown.

Throws:

NoSuchFileException - if the given file does not exist, and the StandardOpenOption.CREATE option was not specified.

IOException - if the file could otherwise not be mapped.

flushAndForce

void flushAndForce()
                   throws IOException

Flush all dirty pages

Throws:

IOException

close

void close()
           throws IOException

Flush all dirty pages and close the page cache.

Specified by:

close in interface AutoCloseable

Throws:

IOException

pageSize

int pageSize()

The size in bytes of the pages managed by this cache.

maxCachedPages

int maxCachedPages()

The max number of cached pages.