CSE 132A Lecture Notes - Lecture 11: Decorrelation, Data Definition Language, Partition Coefficient
8 Nov 2018
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A-a (r s) a-a(r) s. = drinker( frequents beer = bass (serves)) = drinker( frequents bar( beer = bass (serves))) Where b = d and a < c. If you ignore the b"s, you remove all the duplicates of a! No longer static: use partial info about db. Ex: for given algebra query, order of evaluation. Statistical info on data (# tuples, selectivity, etc. ) Is it always better to first join q and r, then join w/ p? (i. e. minimize large intermediate results) no. # tuples for a given attribute is small high selectivity! Index: auxiliary file providing fast access to physical location ofrecord w/ given key value. If tree is balanced, access time is logp(n) for p-ary trees. Can also be created on-the-fly by the query processor! Employ execution primitives for computing relation algebra ops. Smart search of the space of possible plans.
