| 摘要 |
An On-Line Analytic Processing (OLAP) system computes complex expressions and aggregations in queries by re-using and sharing subparts of the expressions and aggregations. A dependency generation phase performed by the OLAP system identifies dependencies among metrics based on the expressions, aggregations, and other metrics used by the metrics. An access plan generation phase performed by the OLAP system generates an access plan based on the identified dependencies, wherein the access plan ensures that expressions, aggregations, and metrics are computed before they are needed, and that required values and intermediate results are passed up a tree structure of the access plan until they are used or consumed by some operator. An operator assignment phase performed by the OLAP system generates operators based on the access plan, and also generates project list expressions, aggregations to be computed in each operator, and input and output tuple types for each operator.
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