org.iq80.leveldb.table

Interface FilterPolicy

All Superinterfaces:

XFilterPolicy

All Known Implementing Classes:

BloomFilterPolicy

public interface FilterPolicy
extends XFilterPolicy

A database can be configured with a custom FilterPolicy object. This object is responsible for creating a small filter from a set of keys. These filters are stored in leveldb and are consulted automatically by leveldb to decide whether or not to read some information from disk. In many cases, a filter can cut down the number of disk seeks form a handful to a single disk seek per DB::Get() call.

Most people will want to use the builtin bloom filter support (see NewBloomFilterPolicy() below).

Author:

Honore Vasconcelos

Method Summary

Modifier and Type	Method and Description
byte[]	createFilter(List<Slice> keys) Append a filter that summarizes keys[0,n-1] to *dst.
boolean	keyMayMatch(Slice key, Slice filter) "filter" contains the data appended by a preceding call to CreateFilter() on this class.
String	name()

Method Detail

name

String name()

createFilter

byte[] createFilter(List<Slice> keys)

Append a filter that summarizes keys[0,n-1] to *dst.

Parameters:

keys - keys[0,n-1] contains a list of keys (potentially with duplicates) that are ordered according to the user supplied comparator.

keyMayMatch

boolean keyMayMatch(Slice key,
                    Slice filter)

"filter" contains the data appended by a preceding call to CreateFilter() on this class. This method must return true if the key was in the list of keys passed to CreateFilter(). This method may return true or false if the key was not on the list, but it should aim to return false with a high probability.