Solr DataImportHandler: Can I get a dynamic field name from xml attribute with XPathEntityProcessor?

Question

I have some XML to ingest into Solr, which sounds like a use case that is intended to be solved by the DataImportHandler. What I want to do is pull the column name from one XML attribute and the value from another attribute. Here is an example of what I mean:

<document>
  <data ref="reference.foo">
    <value>bar</value>
  </data>
</document>

From this xml snippet, I want to add a field with name reference.foo and value bar. The DataImportHandler includes a XPathEntityProcessor for processing XML documents. I've tried using it and it works perfectly if I give it a known column name (e.g, <field column="ref" xpath="/document/data/@ref">) but have not been able to find any documentation or examples to suggest either how to do what I want, or that it cannot be done. So:

• Can I do this using XPathEntityProcessor? If so, how?
• If not, can I do this some other way with DataImportHandler?
• Or am I left with writing my own import handler?

Answer 1

I haven't managed to find a way to do this without bringing in a transformer, but by using a simple ScriptTransformer I worked it out. It goes something like this:

...
<script>
function makePair(row) {
  var theKey = row.get("theKey");
  var theValue = row.get("theValue");

  row.put(theKey, theValue);
  row.remove("theKey");
  row.remove("theValue");

  return row;
}
</script>

...

<entity name="..." 
  processor="XPathEntityProcessor" 
  transformer="script:makePair"
  forEach="/document"
  ...>

  <field column="theKey" xpath="/document/data/@ref" />
  <field column="theValue" xpath="/document/data/value" />
</entity>
...

Hope that helps someone!

Note, if your dynamicField is multivalued, you have to iterate over theKey since row.get("theKey") will be a list.