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Query result size estimation method

A query result, Boolean matrix technology, applied in computing, structured data retrieval, special data processing applications, etc., can solve the problems of inability to eliminate data records, existing estimation accuracy, limited application scope, etc., to achieve fast query speed and storage cost. Low, the effect of improving the estimation accuracy

Active Publication Date: 2015-06-24
HOHAI UNIV
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Problems solved by technology

Although the histogram method can be improved by limiting the error [Wu Shengli, Histogram of Limiting Error, Journal of Computers, Vol.21No.81998.8:704-712], because the histogram method cannot eliminate duplicate data records, fundamentally there is an estimation The defect of precision limits the scope of application

Method used

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Embodiment Construction

[0041] Below in conjunction with specific embodiment, further illustrate the present invention, should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention, after having read the present invention, those skilled in the art will understand various equivalent forms of the present invention All modifications fall within the scope defined by the appended claims of the present application.

[0042] as attached figure 1 As shown, an array IROW is introduced to represent the row number of the truth-valued element in the matrix, and IROW(i) is the row number of the i-th truth-valued element. Here, i=1,2,...,NZ, NZ is true the number of value elements;

[0043] In order to facilitate data insertion, a chain pointer array LNXT is introduced. LNXT(i) indicates the position of the next truth element of the i-th truth element. Each column of truth elements is connected by a chain pointer LNX...

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Abstract

The invention discloses a query result size estimation method, and belongs to the technical field of database management. The method includes the steps of firstly, establishing the one-to-one mapping relation between data object identification and a Boolean matrix element; secondly, establishing the structure of a data record model used for object query counting, and an algorithm of the data record model structure, wherein when a certain object exists, a matrix element, corresponding to a Boolean matrix represented by the data record model, of the object identification is marked as 1, and otherwise the matrix element is marked as 0; thirdly, reading in original data and inserting corresponding records into the data record model, and meanwhile renewing the total number of counted truth-value elements in each line in the data record data; fourthly, converting the range of the queried data identification into the line range of the Boolean matrix, accumulating the total truth-value elements of the matrix lines within the query range, and obtaining the estimated value of the query result size.

Description

technical field [0001] The invention relates to a method for estimating the size of query results, which belongs to the technical field of computer database management. Background technique [0002] The user's demand for data query is becoming more and more complex, so it is necessary to improve the data processing method to achieve efficient complex query. In the implementation of the database system, the query optimizer is generally based on the cost, and the query optimizer compares the cost of various execution schemes , choose the one with the lowest cost to execute. The main problem with estimating cost is estimating the size of query results. Whether the estimation of the size of the query result is accurate or not directly affects the accuracy of the cost estimation of the corresponding scheme, thus having a substantial impact on the quality of the query optimizer. In addition, for large-scale mobile object data management, it is difficult to achieve accurate aggre...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/30
CPCG06F16/1748G06F16/21G06F16/2453
Inventor 冯钧徐斌唐志贤杜丙帅査显月李宗祥王纯陆佳民李士进朱跃龙万定生
Owner HOHAI UNIV
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