| 摘要 |
PROBLEM TO BE SOLVED: To propose a method for improving processing speed of a query. SOLUTION: When inquiry of the query such as SQL is given, conversion into a processing tree composed of a relational operation is performed. When a task capable of being directly processed is present, both the task and a projection operation task are taken out when the next task performing processing to a processing result is a projection operation, and a task wherein the task is combined with the projection operation task is created. The task having a common subexpression is further divided into subgroups. The task wherein a composite relational operation task and/or a composite relational operation is combined based on the task inside the group is created to the subgroup, and the processing of the tasks inside the group is performed at a time. Virtual relation is created to the task inside the subgroup, and relation of a processing result can be partially shared. COPYRIGHT: (C)2009,JPO&INPIT
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