chainindexing

Chain indexing is a data indexing technique used to organize and retrieve items in large datasets by linking index entries into a linear chain. Each node in the chain contains a key and a pointer to the next node, and, in many designs, a reference to the location of the corresponding data record. Chains can be maintained as singly linked lists or as a set of linked blocks on secondary storage. A higher-level index or directory maps search keys to the appropriate chain head, enabling access to the sequence of entries that share a common prefix, bucket, or partition.

In operation, new entries are appended to the end of a chain or inserted at the appropriate position within a chain. If growth occurs beyond a block, the chain can be extended by allocating a new chain segment and updating a predecessor pointer. For lookups, the system follows pointers along the chain until a matching key is found or the chain ends. Chains may be organized per partition or per key range to improve locality and parallelism.

Chain indexing is commonly used in scenarios with high append workloads, long sequential scans, or time-ordered data, such as log archives, time series databases, or archival storage. It is typically simple to implement and has low per-entry overhead, but can yield slower random access if chains become long, and may require housekeeping to manage fragmentation and chain splits.

See also: linked list indexing, inverted index, B-tree, hashing, log-structured merge tree.