Hashing Methods for Temporal Data - Computer Science - Boston ...

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14 IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING, VOL. XXX, NO. XX, XXXXXXX 2001 Fig. 5. a) Query, b) update, and c) space performance for ALH, PPLH-s, PPLH-l, and MVBT methods, using various uniform workloads with varying NB.
KOLLIOS AND TSOTRAS: HASHING METHODS FOR TEMPORAL DATA 15 TABLE 2 Title??? TABLE 3 Notation TABLE 4 Performance Comparison for High NB Values different than the valid-time natural join examined in [33], [40]. There oids were matched as long as the lifespan intervals were intersecting i.e.,the join predicate did not include any specific temporal predicate). Also,our environment is based on transaction-time where changes are in time order. Note that one can easily manipulate the temporal hashing methods to answer interval membership queries ªfind all objects that were in set S during interval Iº). Thus,temporal hashing applies also in joins where the temporal predicate is generalized to an interval,i.e.,find the objects that were both in set X during interval I 1 and in set Y during interval I 2 . Of course,one has to worry about handling artificial oid copies created by the Snapshot Index or the evolving-list approach. However,methodologies have been recently proposed to avoid such copies [4]. It would be an interesting problem to compare indexed temporal joins based on temporal hashing with temporal joins based on MVBT or MVAS indices. Finally,the
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