An efficient multiversion access structure

Abstract

Abstract-An efficient multiversion access structure for a transaction-time database is presented. Our method requires optimal storage and query times for several important queries and logarithmic update times. Three version operations}inserts, updates, and deletes}are allowed on the current database, while queries are allowed on any version, present or past. The following query operations are performed in optimal query time: key range search, key history search, and time range view. The key-range query retrieves all records having keys in a specified key range at a specified time; the key history query retrieves all records with a given key in a specified time range; and the time range view query retrieves all records that were current during a specified time interval. Special cases of these queries include the key search query, which retrieves a particular version of a record, and the snapshot query which reconstructs the database at some past time. To the best of our knowledge no previous multiversion access structure simultaneously supports all these query and version operations within these time and space bounds. The bounds on query operations are worst case per operation, while those for storage space and version operations are (worst-case) amortized over a sequence of version operations. Simulation results show that good storage utilization and query performance is obtained.

Benchmarking access methods for time-evolving regional data

“…It is also interesting that, even if the MVAS improves significantly the overall space used by MVBT in the temporal domain [27], the existence of batch inserts, deletes and updates per transaction time in the case of time-evolving regional data reduces this efficiency in MVASERI in comparison to MVLQ. However, it remains better than MVLQ in all our experiments.…”

“…The Multiversion B-tree (MVBT, [1]) indexes the evolution of one-dimensional data in transaction-time databases. The Multiversion Access Structure (MVAS, [27]) is similar to the MVBT. However, it demands smaller space requirements by using better policies for splits and merges.…”

“…If there is not enough space in the leaf and an overflow occurs, then two thresholds control this process: P MVASERI cons and P MVASERI high , where 4 Â P MVASERI cons 6 P MVASERI high 6 b (for details see [27]). An overflow in leaf A is handled by using the StartTime field and the number of alive records L A .…”

“…The initial motivation for the MVASERI design comes from the Multiversion Access Structure (MVAS, [27]). However, the new approach could be also viewed as a modified MVLQ or as another partial persistent variant of the ''ephemeral'' Linear Quadtree, designed as a directed acyclic graph of pages.…”

“…According to [27], the two thresholds used in MVASERI index construction are set to: P MVSERI high ¼ 0:80 Â b and P MVSERI low ¼ 0:20 Â b, respectively, for b P 5 and any analogy on quadcode inserts, deletes and updates. Also, according to [9] we set TSLQ P TSLQ high ¼ 2=3 Â b.…”