Bucketflush

Bucketflush is a term used in data systems to describe the operation of clearing or persisting the contents of a bucket, a fixed subdivision used to partition data for performance. In bucketed data structures such as hash tables, caches, or time-series stores, data items are assigned to buckets based on a key or temporal attribute. A flush removes entries from one or more buckets, with possible goals of freeing memory, persisting data, or updating secondary storage.

There are two common flavors of bucketflush. In a write-back flush, modified entries are kept in the bucket and written to storage during the flush, after which the in-memory copy is marked clean. In a write-through flush, writes are sent to storage immediately, and the flush mainly reclaims memory. Flushing can be triggered by capacity thresholds, age of data, or explicit commands, and it can be performed on a per-bucket basis or globally across all buckets.

Applications of bucketflush appear in in-memory caches with bucketed sharding, log-structured storage systems, and time-series databases that group data by time windows. It helps manage memory pressure, control write amplification, and improve long-term storage performance by batching writes.

Considerations for bucketflush include data durability and consistency, crash recovery implications, and potential performance impact during the flush. Ordering guarantees across buckets may also be a concern in systems requiring strict monotonicity or transactional semantics.

See also: cache eviction, flush operation, write-back cache, bucketed storage.