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Method for realizing optimization of data source extensive makeup language (XML) query system based on sub-queries

A query system and sub-query technology, which is applied in the field of data source XML query system optimization based on sub-queries, can solve problems such as low efficiency, and achieve the effects of wide application range, convenient processing, and stable and reliable work performance

Inactive Publication Date: 2011-03-09
SHANGHAI GONGJIN COMM TECH
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Problems solved by technology

However, the database object manipulated by the query statement may not only be the basic table of the database, but also a view. If the query processor directly manipulates the view, the only option for the execution plan generated by the query optimizer is to execute the view definition first. Then use the query result of the view as a temporary table to participate in the rest of the query processing, which is extremely inefficient in most cases

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  • Method for realizing optimization of data source extensive makeup language (XML) query system based on sub-queries
  • Method for realizing optimization of data source extensive makeup language (XML) query system based on sub-queries
  • Method for realizing optimization of data source extensive makeup language (XML) query system based on sub-queries

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example 12

[0103] Example 1.2: For query Q and view V in Example 11, when the following view V1 is given:

[0104] Vl:v1(A,B):-p 1 (A,C),p 2 (C,B),p 0 (D,E)

[0105] The following query E is Q based on V and V 1 A complete rewrite of:

[0106] E:q(X,U):-v(X,Z),v 1 (X,U)

[0107] What needs to be explained here is that the entire rewriting process is not performed in a single step, that is, it does not use the view V to rewrite first, and then merge V 1 and the result just now to get the final rewrite of E; use V and V 1 The process of rewriting both views is done in parallel.

[0108] Definition 1.3: Contains mappings. In terms of form, a query Q 1 to another query Q 2 The inclusive map refers to the Q 1 to Q 2 variable mapping such that Q 1 Each basic formula in can be mapped to Q 2 in each of the basic formulas. In fact, to show that Q 1 Contains Q 2 , the containment map should also contain the 1 Query head to Q 2 A map of query headers. But for the convenience of...

example 13

[0118] Example 1.3: For a given query Q: q(X, Y, U, W): -p(X, Y), r(U, W), r(W, U) and a view V: v(A, B , C, D):-p(A, B), r(C, D), C≤D, there is no Q-based conjunction query rewriting that does not introduce new variables.

[0119] However, E:q(X,Y,U,W):-v(X,Y,C,D),r(U,W),r(W,U) is a rewrite of Q based on V. Further, the disjunctive rewriting of Q based on V that does not introduce new variables is:

[0120] Q': q(X, Y, U, W): -v(X, Y, U, W), r(W, U)

[0121] Q': q(X, Y, U, w): -v(X, Y, U, W), r(U, W)

[0122] An important purpose of using views to rewrite queries is to reduce the cost of computing the original query. Therefore, in order to optimize a query, it is not only necessary to find a rewrite of the query, but also to find the minimum rewrite of the query. Next, we discuss how to reduce the number of redundant basic expressions in rewritten queries, and how to find the minimum rewritten method and its complexity. Finally, it is revealed that there are two independ...

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Abstract

The invention relates to a method for realizing optimization of a data source extensive makeup language (XML) query system based on sub-queries. The method comprises the following steps: receiving corresponding XML query input information; carrying out morphological analysis and syntactic analysis, and verifying the correctness and the validity; if the analysis is successful and the verification is passed, generating an XML analytical syntactic tree; translating the XML analytical syntactic tree, and converting the XML query input information into intermediate logical representation; carrying out rewriting treatment, and generating a target query expression; and calling supported querying and computing engines for querying and computing, and acquiring output query results. By adopting the method for realizing the optimization of the data source XML query system based on the sub-queries, the query rewriting can be used for converting a procedural query into a descriptive query, the sub-queries are optimized, and certain specific sub-queries are rewritten into equivalent attended operation of a plurality of tables by the combination of the sub-queries, thus the levels of query sentences are reduced as much as possible, the treatment of planning optimization can be carried out conveniently, and the method has stable and reliable working performance and wider application range.

Description

technical field [0001] The invention relates to the field of computer external information processing, in particular to the field of heterogeneous data source query technology, and specifically refers to a method for realizing data source XML query system optimization based on sub-queries. Background technique [0002] As enterprises and institutions adopt various independent application systems, while partially improving efficiency, the mutual independence of these systems also sets up obstacles for overall management. They lack a unified interface and information channels that are not connected to each other. Data is usually archived on different databases, mainframes, file servers, and only a few users with privileged access can see the data. [0003] In this way, with the passage of time and the advancement of technology, a series of information islands have been formed. Each department or unit is a data source, and each data source is heterogeneous, so the information a...

Claims

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Application Information

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IPC IPC(8): G06F17/30
Inventor 文纬杨昆严营
Owner SHANGHAI GONGJIN COMM TECH
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