Perprefixcollect

Perprefixcollect is a term used in data processing to describe a collection or aggregation strategy in which items are grouped according to the prefixes of a key or sequence. The approach is commonly employed to support prefix-based queries, incremental indexing, and streaming aggregation over time or content segments.

Conceptually, for a string key, a per-prefix collection assigns the item to one or more prefix groups. In the most common mode, items are mapped to all prefixes of their key (for example, the key 'data' contributes to 'd', 'da', 'dat', and 'data'). This creates a hierarchical set of buckets that can be traversed to answer prefix queries efficiently. Some variants instead attach items only to the longest matching prefix or to a fixed number of initial prefixes.

Implementation typically uses a prefix tree (trie) or a map keyed by prefixes. When a new item arrives, the algorithm updates the appropriate buckets along the path corresponding to its key, potentially with an incremental aggregate (count, sum, min/max) rather than storing every item.

Applications include autocomplete and search indexing, log analysis by ID prefixes, and time-series summarization where events are grouped per leading digits or letters. The technique trades increased memory usage for fast lookups of all items sharing a given prefix.

Considerations include the scale of prefixes, duplicate handling, and the need for pruning or aging when streaming data is unbounded. Perprefixcollect remains a flexible concept rather than a single standardized algorithm, adaptable to various data shapes and query requirements.