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https://issues.apache.org/jira/browse/HIVE-1027?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12797769#action_12797769
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Ning Zhang commented on HIVE-1027:
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Thanks for the detailed explanations. It seems we are supporting XPath 1.0
here. When you say "xpath() returns multiple nodes(list)", do you mean it
returns a serialized XML string representing the list of nodes such as
<a>a1</a><a>a2</a> ...? In this case, do you have a test case for composing
xpath() functions. For example and subquery returns XML string from the result
of xpath() and the outer query takes that input to another xpath*() function?
For (4) I'm sure whether we should interpret of empty list as empty string etc.
We can definitely define the mapping between the XML model to relation model
this way, but it doesn't distinguish the case where the xpath_string() result
is an empty list or it is a single node but the value of the node is empty
(e.g., <a/> vs. no <a> element).
Also all this information is better to be exposed to the wider community (not
only developers) as well. Can you also add all these to the Hive's wiki page?
> 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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