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<p>It is well known that the effectiveness of relational database systems is greatly dependent on the efficiency of the data access strategies. For this reason, much work has been devoted to the development of new access techniques, supported by adequate access structures such as the B/sup +/trees. The effectiveness of the B/sup +/tree also depends on the data distribution characteristics; in particular, poor performance results when the data show strong key value distribution unbalancing. The aim of this paper is to present the partial index: a new access structure that is useful in such cases of unbalancing, as an alternative to the B/sup +/tree unclustered indexes. The access structures are built in the physical design phase, and at execution (or compilation) time, the optimizer chooses the most efficient access path. Thus, integration of the partial indexing technique in the design and in the optimization process are also described.</p>
indexing; relational databases; tree data structures; optimisation; query processing; partial indexing; nonuniform data distributions; relational DBMS; relational database; data access strategies; access structures; B+ tree; data distribution characteristics; performance results; key value distribution unbalancing; access structure; unclustered indexes; physical design phase; execution time; compilation time; optimizer; access path; partial indexing technique; optimization process; query processing

C. Sartori and M. Scalas, "Partial Indexing for Nonuniform Data Distributions in Relational DBMS's," in IEEE Transactions on Knowledge & Data Engineering, vol. 6, no. , pp. 420-429, 1994.
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