| 摘 要： | The three-level query optimization strategy in TDM system is introduced inthis paper,semantic query conversation,accessing path selection,and query taskschedule.This strategy can solve the bottle problems in data transmitting and dataprocessing,and can improve the query processing efficiency of the system.TDM is a tightly-coupled tree-structured database machine.It consists of mul-tiple sub-tree-dements (STEs),shown in Fig.1,An STE is a basic data pro-cessing sub-system.The partitioned database is distributed on the STEs.But thedata in each relation is only stored in the disks of a relevant STE,and is processedparallely by the BCP and the SPs in that STE.The multilevel query optimization
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