在Oracle 10g中对ExtractValue进行性能调整

Question

There is an XML file (20MB), when i try to extract the values using the select statement from the table using the EXTRACTVALUE its taking a very long time(Hrs). The table contains the XML_DATA as XMLTYPE Please suggest me to tune the SQL QUERY OR any other alternative to extract the values from the large xml file

SELECT EXTRACTVALUE (VALUE (Name),'*/Name') FirstName,  
.....   
FROM TB_XML_type,TABLE (XMLSEQUENCE (EXTRACT (xml_data, '*/Name'))) Name

Note : The XML format is user defined.

Answer 1

Setting up a table like yours:

CREATE TABLE TB_XML_TYPE(XML_DATA XMLTYPE);

INSERT INTO TB_XML_TYPE(XML_DATA) 
VALUES (XMLTYPE('<a><Name>name1</Name><Name>name2</Name></a>'));

I am guessing the Name element is right under the root element in your XML. If that's the case, this may be faster.

SELECT XD.NAME FROM TB_XML_TYPE XT, 
    XMLTABLE('/a/Name' PASSING XT.XML_DATA
        COLUMNS NAME VARCHAR2(100) PATH 'text()') XD

Result:

NAME                                                                                               
---------------------
name1                                                                                                
name2                                                                                                

If not, make sure the repeated path is right after XMLTABLE - this is the XPath that finds all the parent elements whose children you then read with the XPath right after the PATH keyword. In this case, text() reads the text contents of the Name element.