| 摘要 |
A database system includes an enhanced optimizer module that is able to consider group-by operations as part of the optimization of a join. Given a query that performs a join of multiple tables and that includes an aggregation function as well as at one of a Where clause and a Group-by clause, a partial group-by is performed on at least one of the tables of the join query to reduce the number of rows for the join. Group-by can also be performed on intermediate results of intermediate joins.
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