Indexand

Indexand is a concept in information retrieval describing a method for combining multiple indexed queries through a logical conjunction. In an indexand workflow, each indexed attribute yields a candidate set of documents; the final result is the intersection of these sets, returning only items that satisfy all conditions.

Origins and usage: The term appears in discussions of advanced boolean querying and multi-field search. It is used to describe an operator or processing pattern rather than a distinct data structure.

Mechanism: Typically built on inverted indexes, where each term or attribute corresponds to a postings list. The indexand operation computes the intersection of postings lists using merge-join techniques or bitset operations. In large-scale systems, compressed bitmap indexes (for example Roaring or WAH) are used to speed intersections, and early termination strategies reduce work when a threshold is met.

Variants and scope: Indexand can operate across multiple fields such as author, date, and tag. Some systems implement indexand as a specialized executor that indexes precomputed intersections or uses scoring to rank results within the intersection.

Example: A query such as author:Smith AND year:2020 AND tag:machine-learning is evaluated by retrieving the documents from each index and intersecting the three result sets.

Applications and limitations: Used in search engines, document databases, and log-analysis tools to implement multi-criteria filtering. Limitations include increased cost with many terms, data skew causing uneven postings lengths, and higher memory usage for large intersections.

See also: boolean query, inverted index, postings list, bitset, set intersection.