A heuristic approach for optimization of path expressions
| Autor: | Asuman Dogac, Cem Evrendilek, Cetin Ozkan |
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| Rok vydání: | 1995 |
| Předmět: | |
| Zdroj: | Lecture Notes in Computer Science ISBN: 9783540603030 DEXA |
| DOI: | 10.1007/bfb0049149 |
| Popis: | The object-oriented database management systems store references to objects (implicit joins, precomputed joins), and use path expressions in query languages. One way of executing path expressions is pointer chasing of precomputed joins. However it has been previously shown that converting implicit joins to explicit joins during the optimization phase may yield better execution plans. A path expression is a linear query, therefore, considering all possible join sequences within a path expression is polynomial in the number of classes involved. Yet, when the implicit joins are converted to explicit joins in a query involving multiple path expressions bound to the same bind variable, the query becomes a star query and thus considering all possible joins is exponential in the number of paths involved. This implies that there is a need for improvement by using heuristic in optimizing queries involving multiple path expressions. |
| Databáze: | OpenAIRE |
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