Based On Algebra Tree's ORDBMS Query Optimization Technology Research And Algorithm Design

The query optimization is an important technology which the DBMS design and the realization uses, is the key aspect affecting. ORDBMS inheriting the relational database technology in the foundation, increased the object-oriented characteristic, may satisfy GIS, CIMS, OIS and so on the emerging domain multi-dimensional data complex query. Therefore, studies based on the ORDBMS query optimization technology has the good development prospect and the commercial value.Take ORDBMS as the data model, in summarizes in the domestic and foreign databases query optimization achievement foundation, analysis existing research in insufficiency, the utilization relations algebra theory and uses the contrast, the decomposition, the seal, the illustration method, take DB2 UDB as the movement platform, proposed a kind of query optimization technology based on the algebra tree's, has solved in the query optimization process about the high price choice predicate, the definition variable connection index structure concrete question.According to chooses in the condition to be possible to contain the user from the definition complex function new characteristic, proposed one kind based on the algebra tree's Rolling_Up query optimization algorithm. In dynamic programming method and the heuristic rule has in the connection order foundation using System R for the connection operation, computation choice condition Rank value, in search execution plan appropriate position. This method expenses are small, also can have the optimized execution plan.Cannot apply directly in view of the original algorithm in the connection condition includes from the definition complex function structure insufficiency, proposed the definition transformation concept, defines the connection predicate variable the value scope, thus avoids to the whole piece relational table scanning, has achieved the enhancement connection algorithm performance goal. At the same time also promoted the connection predicate index to the general form, enabled it to be possible to be suitable for several tables connection.Has confirmed through the concrete example based on the algebra tree's ORDBMS query optimization technology feasibility and the accuracy, and had proven the Rolling_Up optimization algorithm can obtain the high query efficiency in the time.