Written Tutorial

Problem

You want to find all XML documents that are missing a particular element.

Solution

Applies to MarkLogic versions 7+

cts.search(
  cts.notQuery(
    cts.elementQuery(
      xs.QName("target"), 
      cts.trueQuery()
    )
  )
)

cts:search(
  fn:doc(),
  cts:not-query(
    cts:element-query(
      xs:QName("targetElement"), 
      cts:true-query()
    )
  )
)

For MarkLogic 7 and earlier, replace the cts:true-query()with cts:and-query(()).

Discussion

MarkLogic’s built-in search engine uses query criteria to identify matching fragments. The indexes map terms (words, phrases, structures, etc.) to fragment identifiers. To run a search, the specified terms are looked up in the appropriate index to find fragment identifiers. In the case of cts:not-query, the search will return any fragment identifiers except those matched by the nested query.

cts:element-query is a useful way to constrain a search to part of a document. The function restricts the nested query to matching within the specified XML element.

The query passed to cts:element-query is cts:true-query for MarkLogic 8 and above and cts:and-query(()) for MarkLogic 7 and before. cts:true-query does what it sounds like — it matches everything. Passed to cts:element-query, this provides a simple way to test for the existence of an element. If you’re using a version of MarkLogic that predates cts:true-query, the way to simulate it is to use cts:and-query and pass in the empty sequence to it. An and-query matches if all queries passed into are true; if none are passed in, then it matches, thus making cts:and-query(()) work the same as cts:true-query.