Tempindices

Tempindices are temporary index structures created to accelerate intermediate computations. They are typically ephemeral and discarded once the associated operation finishes, serving as a performance aid rather than a persistent data artifact. By mapping keys to records, positions, or pointers, tempindices allow fast lookups during a calculation that would otherwise require repeated searches.

In database systems, tempindices commonly arise during complex query execution. They can support hash joins, merge joins with pre-sorted input, or grouping and distinct operations. Depending on size and configuration, a tempindex may be built in memory or spilled to disk, and it is generally released when the query completes or the plan is dismantled. Temporary indices are usually transparent to users and are not stored as part of the database schema.

In algorithms and data processing, tempindices appear as transient hash tables, arrays, or other mapping structures used to reduce redundant work. They enable efficient neighbor lookups, position tracking, or stage-wise sorting without committing to long-term storage.

Implementation considerations for tempindices include the choice of data structure, memory usage, and concurrency controls. Designers weigh the benefits of faster lookups against the overhead of creating and destroying the structure, as well as the risk of memory pressure or spill-to-disk behavior.

Related concepts include temporary tables, materialized views, and other ephemeral data structures used to optimize performance during compute workflows.