Longindex

Longindex is a theoretical and practical approach to indexing designed for efficiently handling very long keys, such as long documents, program source code, or genomic sequences. It aims to provide fast lookups and scalable storage for large collections where traditional indexes may falter due to key length or volume.

The design principle often combines a compressed, prefix-based data structure with an auxiliary inverted index. A multi-level or compact prefix tree stores common prefixes of long keys to reduce redundancy, while the inverted index maps long tokens or features to the documents that contain them. This hybrid arrangement supports fast exact lookups and can enable prefix, range, or substring queries depending on the implementation. Longindex implementations typically use blockwise storage, delta encoding, and compression to scale, and may support dynamic updates with deferred consolidation to maintain performance.

Core operations include insert, delete, update, and query. Queries return documents or pointers to them, and may include scoring or ranking information. Trade-offs involve memory usage versus lookup speed and the complexity of updates. In practice, longindex is used in contexts where long identifiers or texts are common, such as full-text search over large corpora, genome data indexing, or large-scale code search.

Limitations include higher implementation and maintenance costs compared with traditional B-trees or standard inverted indexes. Longindex is typically embedded within broader search or database systems rather than offered as a standalone, general-purpose component. See also: trie, suffix tree, suffix array, B-tree, inverted index, and n-gram indexing.