Module cuckoo_filter

Description
Data Types
Function Index
Function Details

High-performance, concurrent, and mutable Cuckoo Filter implemented using atomics for Erlang and Elixir.

Description

High-performance, concurrent, and mutable Cuckoo Filter implemented using atomics for Erlang and Elixir.

Data Types

option()

option() = {name, filter_name()} | {fingerprint_size, 4 | 8 | 16 | 32 | 64} | {bucket_size, pos_integer()} | {max_evictions, non_neg_integer()} | {hash_function, fun((binary()) -> hash())}

Function Index

add/2	Equivalent to `add(Filter, Element, infinity)`.
add/3	Adds an element to a filter.
add_hash/2	Equivalent to `add_hash(Filter, Element, infinity)`.
add_hash/3	Adds an element to a filter by its hash.
capacity/1	Returns the maximum capacity of a filter.
contains/2	Checks if an element is in a filter.
contains_fingerprint/3	Checks whether a filter contains a fingerprint at the given index or its alternative index.
contains_hash/2	Checks if an element is in a filter by its hash.
delete/2	Equivalent to `delete(Filter, Element, infinity)`.
delete/3	Deletes an element from a filter.
delete_hash/2	Equivalent to `delete_hash(Filter, Element, infinity)`.
delete_hash/3	Deletes an element from a filter by its hash.
export/1	Exports a filter as a binary.
hash/2	Returns the hash value of an element using the hash function of the filter.
import/2	Imports filter data from a binary created using `export/1`.
new/1	Equivalent to `new(Capacity, [])`.
new/2	Creates a new cuckoo filter with the given capacity and options.
size/1	Returns number of items in a filter.
whereis/1	Retrieves a cuckoo_filter from persistent_term by its name.

Function Details

add/2

add(Filter::cuckoo_filter() | filter_name(), Element::term()) -> ok | {error, not_enough_space}

Equivalent to add(Filter, Element, infinity).

add/3

add(Filter::cuckoo_filter() | filter_name(), Element::term(), LockTimeout::timeout()) -> ok | {error, not_enough_space | timeout}

add(Filter::cuckoo_filter() | filter_name(), Element::term(), LockTimeout::force) -> ok | {ok, Evicted::{index(), fingerprint()}}

Adds an element to a filter.

Returns ok if the insertion was successful, but could return {error, not_enough_space}, when the filter is nearing its capacity.

When LockTimeout is given, it could return {error, timeout}, if it can not acquire the lock within LockTimeout milliseconds.

If force is given as the 3rd argument, and there is no room for the element to be inserted, another random element is removed, and the removed element is returned as {ok, {Index, Fingerprint}}. In this case, elements are not relocated, and no lock is acquired.

add_hash/2

add_hash(Filter::cuckoo_filter() | filter_name(), Hash::hash()) -> ok | {error, not_enough_space}

Equivalent to add_hash(Filter, Element, infinity).

add_hash/3

add_hash(Filter::cuckoo_filter() | filter_name(), Hash::hash(), LockTimeout::timeout()) -> ok | {error, not_enough_space | timeout}

add_hash(Filter::cuckoo_filter() | filter_name(), Hash::hash(), LockTimeout::force) -> ok | {ok, Evicted::{index(), fingerprint()}}

Adds an element to a filter by its hash.

Same as add/3 except that it accepts the hash of the element instead of the element.

capacity/1

capacity(Cuckoo_filter::cuckoo_filter() | filter_name()) -> pos_integer()

Returns the maximum capacity of a filter.

contains/2

contains(Filter::cuckoo_filter() | filter_name(), Element::term()) -> boolean()

Checks if an element is in a filter.

contains_fingerprint/3

contains_fingerprint(Filter::cuckoo_filter() | filter_name(), Index::index(), Fingerprint::fingerprint()) -> boolean()

Checks whether a filter contains a fingerprint at the given index or its alternative index.

contains_hash/2

contains_hash(Filter::cuckoo_filter() | filter_name(), Hash::hash()) -> boolean()

Checks if an element is in a filter by its hash.

delete/2

delete(Filter::cuckoo_filter() | filter_name(), Element::term()) -> ok | {error, not_found}

Equivalent to delete(Filter, Element, infinity).

delete/3

delete(Filter::cuckoo_filter() | filter_name(), Element::term(), LockTimeout::timeout()) -> ok | {error, not_found | timeout}

Deletes an element from a filter.

Returns ok if the deletion was successful, and returns {error, not_found} if the element could not be found in the filter.

When LockTimeout is given, it could return {error, timeout}, if it can not acquire the lock within LockTimeout milliseconds.

Note: A cuckoo filter can only delete items that are known to be inserted before. Deleting of non inserted items might lead to deletion of another random element.

delete_hash/2

delete_hash(Filter::cuckoo_filter() | filter_name(), Hash::hash()) -> ok | {error, not_found}

Equivalent to delete_hash(Filter, Element, infinity).

delete_hash/3

delete_hash(Filter::cuckoo_filter() | filter_name(), Hash::hash(), LockTimeout::timeout()) -> ok | {error, not_found | timeout}

Deletes an element from a filter by its hash.

Same as delete/3 except that it uses the hash of the element instead of the element.

export/1

export(Filter::cuckoo_filter() | filter_name()) -> binary()

Exports a filter as a binary.

Returned binary can be used to reconstruct the filter again, using import/2 function.

hash/2

hash(Cuckoo_filter::cuckoo_filter() | filter_name(), Element::term()) -> hash()

Returns the hash value of an element using the hash function of the filter.

import/2

import(Filter::cuckoo_filter() | filter_name(), Data::binary()) -> ok | {error, invalid_data_size}

Imports filter data from a binary created using export/1.

Returns ok if the import was successful, but could return {ok, invalid_data_size} if the size of the given binary does not match the size of the filter.

new/1

new(Capacity::pos_integer()) -> cuckoo_filter()

Equivalent to new(Capacity, []).

new/2

new(Capacity::pos_integer(), Opts::options()) -> cuckoo_filter()

Creates a new cuckoo filter with the given capacity and options

Note that the actual capacity might be higher than the given capacity, because internally number of buckets in a cuckoo filter must be a power of 2.

Possible options are:

{name, Name}
If you give it a name, created filter instance will be stored in persistent_term, and later you can access the filter by its name.
{fingerprint_size, FingerprintSize}
FingerprintSize can be one of 4, 8, 16, 32, and 64 bits. Default fingerprint size is 16 bits.
{bucket_size, BucketSize}
BucketSize must be a non negative integer, and the default value is 4. Higher bucket sizes can reduce insert time considerably since it reduces the number of relocations of existing fingerprints in occupied buckets, but it increases the lookup time, and false positive rate.
{max_evictions, MaxEvictions}
MaxEvictions indicates the maximum number of relocation attemps before giving up when inserting a new element.
{hash_function, HashFunction}
You can specify a custom hash function that accepts a binary as argument and returns hash value as an integer. By default xxh3 hash functions are used, and you need to manually add xxh3 to the list of your project dependencies.

size/1

size(Cuckoo_filter::cuckoo_filter() | filter_name()) -> non_neg_integer()

Returns number of items in a filter.

whereis/1

whereis(FilterName::filter_name()) -> cuckoo_filter()

Retrieves a cuckoo_filter from persistent_term by its name.

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