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From tuedel <>
Subject Distinct values in multivalued fields
Date Mon, 01 Jul 2013 13:34:54 GMT
Hello everybody,

i have tried to make use of the UniqFieldsUpdateProcessorFactory in 
order to achieve distinct values in multivalued fields. Example below: 

<updateRequestProcessorChain name="uniq_fields"> 
     <lst name="fields"> 
   <processor class="solr.RunUpdateProcessorFactory" /> 

<requestHandler name="/update" class="solr.UpdateRequestHandler"> 
   <lst name="defaults"> 
      <str name="update.chain">uniq_fields</str> 

However the data being is indexed one by one. This may happen, since a 
document may will get an additional tag in a future update. Unfortunately in 
order to ensure not having any duplicate tags, i was hoping, the 
UpdateProcessorFactory is doing what i want to achieve. In order to actually 
add a tag, i am sending an 

"tag_type" :{"add":"foo"}, which still adds the tag, without questioning if 
its already part of the field. How may i be able to achieve distinct values 
on solr side?! 

In order to achieve this behavior i suggest writing an own processor might
be a solution. However i am uncertain how to do and if it's the proper way. 
Imagine an incoming update - e.g. an update of an existing document having
several multivalued fields without specifying "add" or "set". This task
would cause the corresponding document to get dropped and re-indexed without
keeping any previously added values within the multivalued field. 
Therefore if a field is getting updated and not having the distinct value
being part of the index yet, shall add the value, otherwise ignore it. The
processor needs to define whether a field is getting added to the index or
not in condition of the existing index. Is that achievable on Solr side?! 
Below my current pretty empty processor class:

public class ConditionalSolrUniqFieldValuesProcessorFactory extends
UpdateRequestProcessorFactory {

    public UpdateRequestProcessor getInstance(SolrQueryRequest sqr,
SolrQueryResponse sqr1, UpdateRequestProcessor urp) {
        return new ConditionalUniqFieldValuesProcessor(urp);

    class ConditionalUniqFieldValuesProcessor extends UpdateRequestProcessor

        public ConditionalUniqFieldValuesProcessor(UpdateRequestProcessor
next) {

        public void processAdd(AddUpdateCommand cmd) throws IOException {
            SolrInputDocument doc = cmd.getSolrInputDocument();

            Collection<String> incomingFieldNames = doc.getFieldNames();
            for (String t : incomingFieldNames) {
                is multivalued
                if (doc.getField(t).) { 
                    If multivalued and already part of index, drop from
index. Otherwise add to multivalued field.

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