NAME

Concurrent::Trie - A lock-free concurrent trie (Text Retrieval) data structure

SYNOPSIS

use Concurrent::Trie;

my $trie = Concurrent::Trie.new;
say $trie.contains('brie');  # False
say so $trie;                # False
say $trie.elems;             # 0

$trie.insert('brie');
say $trie.contains('brie');  # True
say so $trie;                # True
say $trie.elems;             # 1

$trie.insert('babybel');
$trie.insert('gorgonzola');
say $trie.elems;             # 3
say $trie.entries();         # (gorgonzola babybel brie)
say $trie.entries('b');      # (babybel brie)

DESCRIPTION

A trie stores strings as a tree, with each level in the tree representing a character in the string (so the tree's maximum depth is equal to the number of characters in the longest entry). A trie is especially useful for prefix searches, where all entries with a given prefix are required, since this is obtained simply by walking the tree according to the prefix, and then visiting all nodes below that point to find entries.

This is a lock-free trie. Checking if the trie contains a particular string never blocks. Iterating the entries never blocks either, and will provide a snapshot of all the entries at the time the entries` method was called. An insertion uses optimistic concurrency control, building an updated tree and then trying to commit it. This offers a global progress bound: if one thread fails to insert, it's because another thread did a successful insert.

This data structure is well suited to auto-complete style features in concurrent applications, where new entries and lookups may occur when, for example, processing web requests in parallel.

Methods

insert(Str $value --> Nil)

Inserts the passed string value into the trie.

contains(Str $value --> Bool:D)

Checks if the passed string value is in the trie. Returns True if so, and False otherwise.

entries($prefix = '' --> Seq:D)

Returns a lazy iterator of all entries in the trie with the specified prefix. If no prefix is passed, the default is the empty prefix, meaning that a call like $trie.entries() will iterate all entries in the trie. The order of the results is not defined.

The results will be a snapshot of what was in the trie at the point entries was called; additions after that point will not be in the entries list.

elems(--> Int:D)

Gets the number of entries in the trie. The data structure maintains a count, making this O(1) (as opposed to $trie.entries.elems, which would be O(n)).

Bool(--> Bool:D)

Returns True if the number of entries in the trie is non-zero, and False otherwise.

AUTHOR

Jonathan Worthington

COPYRIGHT AND LICENSE

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.