Research and implementation of table-join Hint for precision control on execution plan
HE Qing-fa · Jisuanji gongcheng yu sheji · 2010
To resolve the problem of precision control on execution plan with table-join Hint,which is caused by the enormous execution plan space when several tables are joined for a query request,a table-join Hint control model based on the join operator of relational algebra is proposed.In this model,a bijection between table-join Hint and optimizer execution plan is defined to provide maintenance of accuracy for every part of the plan,without any modification of the existing theory of optimizer construction.Furthermore,a conflict-estimation rule is presented,which can not only be used to figure out the result of semantic conflict among all sorts of table-join Hints quickly and exactly when the Hints have the different set of table parameters,but also provide the excellent extensibility for the control model.Finally,both effectivity and efficiency of this model are testified in Shenzhou OSCAR database.