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Ιδρυματικό Αποθετήριο [SANDBOX]
Πολυτεχνείο Κρήτης
Πολυτεχνείο Κρήτης
EN
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EL
| URI: | http://purl.tuc.gr/dl/dias/FA5231DA-D168-4CB2-AA1A-FDAF32CF9E93 | ||
| Έτος | 1984 | ||
| Τύπος | Δημοσίευση σε Περιοδικό με Κριτές | ||
| Άδεια Χρήσης |
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| Βιβλιογραφική Αναφορά | S. Christodoulakis, "Estimating block selectivities", Information Systems, vol. 9, no. 1, pp. 69-79, 1984. doi: 10.1016/0306-4379(84)90017-6 https://doi.org/10.1016/0306-4379(84)90017-6 | ||
| Εμφανίζεται στις Συλλογές |
In many data base performance studies there is a need to estimate the number of records of a file which qualify in a query, as well as the number of blocks of secondary storage which contain these records. In this paper we present a model of data base contents and data placement on devices. We extend a multivariate statistical model that was used for the estimation of record selectivities in [5] to model the distribution of records that qualify in a query among the blocks of secondary storage. Then we show how to obtain estimates of block selectivities and we compare our estimates with the estimates of previous models.
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