How to update the existing field of solr index using java? - solr

Question

I have a Solr index in a core having 3000 documents.
I want to modify the value of a single field in the entire core based on unique key PaperID.
I'm using the following java code but instead of updating the existing value it adds new documents.
if (solrDocument.get("PaperID").equals(solrDocument2.get("PaperID"))) {
String Mscore = (String) solrDocument.get("ID");
String ModifyScore = (String) solrDocument.get("Author");
//solrDocument.setField("ID", ModifyScore);
//update the field
System.out.println(Mscore);
System.out.println(ModifyScore);
System.out.println(solrDocument2.get("Mscore") + "\n");
SolrInputDocument sid = new SolrInputDocument();
Map<String, Object> fieldModifier = new HashMap<String, Object>(1);
fieldModifier.put("set", ModifyScore);
sid.setField("ID", fieldModifier);
//solr.add(sid);
solr.commit();
}
can anyone guide me accordingly...Best Regards

Answer 1

Your code isn't changing anything, since you've commented out the .add command. And you have to use the actual ID in the ID field, since Solr won't know what document to update otherwise. The field you're changing should have the fieldModifier attached:
SolrInputDocument doc = new SolrInputDocument();
Map<String, String> fieldModifier = new HashMap<String, String>();
// Change ModifyScore to the new value, since you're just using the current value now..
fieldModifier.put("set", ModifyScore);
doc.addField("ID", Mscore);
doc.addField("Author", fieldModifier);
solr.add(doc);
solr.commit();