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A query method for xml data

A query method and data technology, applied in the database field, can solve the problem of high IO cost, and achieve the effect of efficient and effective query and management

Inactive Publication Date: 2016-12-07
PEKING UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The TurboXpath function is relatively sound, but for the XML data in the database, the TurboXPath algorithm scans the XML document from the beginning to the end, and the IO cost is very high, especially for those larger XML documents

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  • A query method for xml data
  • A query method for xml data
  • A query method for xml data

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Embodiment Construction

[0031] The present invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0032] figure 1 It is the flow chart of the XML data query method of the present invention, and the concrete steps include:

[0033] 1) Use Native XML to store XML data in the database.

[0034] The XML data query method of the invention belongs to the overall twig connection method. Compared with the early structured connection, the overall twig connection technology can avoid a large number of invalid intermediate results. The basis of the method of the invention is Native XML storage, and the DDE coding mode is adopted for the XML elements. The native storage mechanism maintains the document order of XML elements, and through the physical address of an element's opening tag, the sub-documents with the element as the root can be retrieved. DDE encoding is used to judge the common structural relationships of XML elements (ancestor...

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Abstract

The invention provides a query method for XML (Extensive Makeup Language) data. The query method comprises the following steps: (1) adopting a Native XML manner to store the XML data, wherein a storage structure comprises an inner node layer, a leaf node layer and an inverted layer, wherein the inner node layer is used for storing nodes of an XML tree, an XML element is encoded by adopting a DDE (Dynamic Data Exchange) encoding manner, the leaf node layer is used for storing file data of the nodes of the XML tree; the inverted layer is used for storing an inverted index of the leaf node layer; (2) taking out an element sequence corresponding to the nodes of an XPath from the inverted layer according to an input XPath query statement and carrying out merge sort by adopting a loser tree; and (3) carrying out pushing and popping operation on XML elements subjected to the merge sort according to the sequence and obtaining a query result from a buffering region. According to the query method for the XML data, the XPath with a keyword OR and a wildcard character * can be processed and the efficiency is very high.

Description

technical field [0001] The invention belongs to the technical field of databases, relates to a storage and query method for semi-structured data XML, in particular to an XML data query method that can effectively support the XML query language XPath. Background technique [0002] As more and more application systems use XML as a standard format to publish and exchange data, the scale of XML data has expanded dramatically. According to a recent report by IDC (Internet Data Center), among the IT departments of 500 respondents 29% are making heavy use of XML documents and XML databases. How to manage XML data effectively has become an urgent problem to be solved. [0003] Quickly and accurately finding all matching elements of XPath in XML database is the core operation of XML query processing. For example, an XPath expression: book[title='XML'] / / author[fn='Jane'AND ln='Doe'], the node author matched by this expression needs to satisfy: 1) There is a child node fn, Its conte...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06F17/30
CPCG06F16/81G06F16/835
Inventor 郭少松包小源陈薇王腾蛟杨冬青
Owner PEKING UNIV
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