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From "Ning Zhang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1027) Create UDFs for XPath expression evaluation
Date Thu, 07 Jan 2010 01:18:54 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12797427#action_12797427
] 

Ning Zhang commented on HIVE-1027:
----------------------------------

This is cool stuff. Just some questions:
1) In general XPath queries return a list of nodes. What is the semantics of xpath_double
(eg.) return if XPath evaluates to multiple nodes. 
2) Is the XPath query parsed for every input row, or only parsed once?
3) Do you support DTD and XMLSchema? What about namespace and backward axes in XPath?
4) If XPath evaluates to empty list, do you return NULL or empty string (in case of xpath())?
 

> Create UDFs for XPath expression evaluation
> -------------------------------------------
>
>                 Key: HIVE-1027
>                 URL: https://issues.apache.org/jira/browse/HIVE-1027
>             Project: Hadoop Hive
>          Issue Type: New Feature
>          Components: Query Processor
>            Reporter: Patrick Angeles
>            Assignee: Patrick Angeles
>            Priority: Minor
>         Attachments: hive-1027.patch, udf_xpath.patch
>
>
> Create UDFs for evaluating XPath expressions against XML documents.
> Examples:
> > SELECT xpath_double ('<a><b class="odd">1</b><b class="even">2</b><b
class="odd">4</b><c>8</c></a>', 'sum(a/b[@class="odd"])') FROM
src LIMIT 1 ;
> 5.0
> > SELECT xpath_string ('<a><b>b1</b><b>b2</b></a>',
'a/b[2]') FROM src LIMIT 1 ;
> b2
> > SELECT xpath ('<a><b>b1</b><b>b2</b><b>b3</b><c>c1</c><c>c2</c></a>',
'a/c/text()') FROM src LIMIT 1 ;
> ["c1","c2"]
> Included functions are: xpath_short, xpath_int, xpath_long, xpath_float, xpath_double/xpath_number,
xpath_string, xpath

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