Is Marklogic search with position possible? - xquery

Question

There is some explanation of a use case below; the actual question follows.
I am using ML search queries on some documents that contain elements of the form:
<resource>
<version>
<metadata label="author">Jim</metadata>
...
</version>
<version>
<metadata label="author">John</metadata>
...
</version>
</resource>
Note the versioning of metadata. Uppermost version element contains up-to-date info for the document.
The queries are based on user input; the user looks e. g. for documents, whose author is John.
I am not knowledgeable enough to combine attribute value and element/text value queries in a better way than this:
cts:near-query((cts:element-attribute-value-query(xs:QName("metadata"), xs:QName("label"), "author"), cts:element-value-query(xs:QName("metadata"), "John")), 0)
It does work though, so I am fine with it. What doesn't work is choosing only the last version in the resource (/resource/version[1]). If, at a certain point, the "author" was changed from "John" to "Jim", the document with the resource as shown above will always be found, because I don't know how to look only for values in the last (uppermost) version element. So I have to filter the results once more over XPath in a loop.
Is there a way to do this on an ML search query level?

Answer 1

You could create a field with a path that points to the metadata with the #label="author" that is in the first version element: /resource/version[1]/metadata[#label="author"] and then you could use a cts:field-value-query()
Then you could search that named field:
cts:search(doc(), cts:field-value-query("author", "John"))

Answer 2

Just through xPath, someone (yourself or MarkLogic) will have to take the hit of filtering on the value you want. This is even the case for using a searchable expressions and using the filtering option. Such is the case of repeating elements in a document.
The most efficient way is to index the path in question separately and then query against that value.
Some options:
TDE Template to extract the value. Even though extremely powerful and likely my choice, it steps away from your simple example, so I will pass on that example.
Range Index. Nice, but memory mapped assuming that you want to do range queries - but your query is on a simple value query, so we will skip this
Field. Simple, elegant and what is needed here. Define the xPath to exactly what you want and a second-pass indexing will pull that value out and index it separately with its own indexing rules. you can then query this value.
Please note the semi-colon (;) -there are three separate executions here. (1) field creation, (2) document insert and (3) search.
xquery version "1.0-ml";
import module namespace admin = "http://marklogic.com/xdmp/admin"
at "/MarkLogic/admin.xqy";
let $config := admin:get-configuration()
let $dbid := xdmp:database("Documents")
let $field-name := "latest-resource"
return
if(empty(admin:database-get-fields($config, $dbid)[./*:field-name="latest-resource"]))
then
let $field-spec := <field xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://marklogic.com/xdmp/database">
<field-name>{$field-name}</field-name>
<field-path><path>/resource/version[./metadata/#label="author"][1]</path>
<weight>1.0</weight>
</field-path>
<word-searches>false</word-searches>
<field-value-searches>true</field-value-searches>
</field>
let $_ := admin:save-configuration(admin:database-add-field($config,$dbid,$field-spec))
return ()
else ();
(:--------------------------------------------:)
(
xdmp:document-insert("/sample/jim-first.xml", <resource>
<version>
<metadata label="author">Jim</metadata>
</version>
<version>
<metadata label="author">John</metadata>
</version>
</resource>),
xdmp:document-insert("/sample/john-first.xml", <resource>
<version>
<metadata label="author">John</metadata>
</version>
<version>
<metadata label="author">Jim</metadata>
</version>
</resource>)
);
(: ----------------------------------------------------- :)
cts:search(doc(), cts:field-value-query("latest-resource", "Jim"))
In this case, only Jim is returned where he is in the first version.
<resource>
<version>
<metadata label="author">Jim</metadata>
</version>
<version>
<metadata label="author">John</metadata>
</version>
</resource>