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Efficient processing of aggregation queries is essential for decision support applications. This paper describes a class of query transformations , called eager aggregation and laty aggregation, that allows a query optimizer to move group-by operations up and down the query tree. Eager aggregation partially pushes a groupby past a join. After a group-by is(More)
Assume that we have an SQL query containing joins and a group-by. The standard way of evaluating this type of query is to rst perform all the joins and then the group-by operation. However, it may be possible to perform the group-by early, that is, to push the group-by operation past one or more joins. Early grouping may reduce the query processing cost by(More)
SQL queries containing GROUP BY and aggre-gation occur frequently in decision support applications. Grouping with aggregation is typically done by rst sorting the input and then performing the aggregation as part of the output phase of the sort. The most widely used external sorting algorithm is merge sort, consisting of a run formation phase followed by a(More)
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