Xquery

Queries an XML document using the Xquery language.

Usage

xquery (indata, xml-attr, xquery : outdata)

Details

XML data stored in attribute xml-attr of relation indata is queried using xquery, with its results stored in outdata, joined back with its input (i.e., a dependent join). Queries are processed using the SAXON XQuery SDK.

Notes

This version of Xquery replaces the earlier Quip-based version.
xml-attr can be either a CHAR or DOCUMENT relational attribute type. The latter is usually obtained from a prior Xwrapper or Rel2xml operator. In the case of the former, the data must be legal XML and is internally converted into a Document before processing.

Known Bugs

None.

Example

Using the input:

      RELATION document: xmltext char
      <?xml version="1.0"?> <books> <book> <title>Title1</title> <author>Author1</author> </book> <book> <title>Title2</title> <author>Author2</author> </book> <book><title>Title3</title> <author>Author1</author> </book> </books>
      RELATION query: dummy char
      <titles> { for $b in ./books/book where $b/author/text() = "Author1" return $b/title } </titles>

when executing the plan:

      PLAN test
      {
        INPUT: stream document, stream query
        OUTPUT: stream result

        BODY
        {
          xquery (document, "xmltext", query, "answer_doc" : query-result)
          xml2rel (query-result, "answer_doc", "/titles", "index" : result)
        }
      }

OR:

      PLAN test
      {
        INPUT: stream document
        OUTPUT: stream result

        BODY
        {
          xquery (document, "xmltext", "<titles> { for $b in ./books/book where $b/author/text() = \"Author1\" return $b/title } </titles>", "answer_doc" : query-result)
          xml2rel (query-result, "answer_doc", "/titles", "index" : result)
        }
      }

generates the following output:

      ----------------------------------------------
      RELATION: uxquery1_result
         attrs: index, xmltext, answer_doc, title
      ----------------------------------------------
      0|<?xml version="1.0"?> <books> <book> <title>Title1</title> <author>Author1</author> </book> <book> <title>Title2</title> <author>Author2</author> </book> <book> <title>Title3</title> <author>Author1</author> </book> </books>, <?xml version="1.0" encoding="UTF-8"?> 
              <titles>
                      <title>Title1</title>
                      <title>Title3</title>
              </titles>|Title1
      1|<?xml version="1.0"?> <books> <book> <title>Title1</title> <author>Author1</author> </book> <book> <title>Title2</title> <author>Author2</author> </book> <book> <title>Title3</title> <author>Author1</author> </book> </books>, <?xml version="1.0" encoding="UTF-8"?> 
              <titles>
                      <title>Title1</title>
                      <title>Title3</title>
              </titles>|Title3
      ----------------------------------------------