Over a million developers have joined DZone.

Automatically Generate Document Identifiers – Solr 4.x

· Big Data Zone

Learn how you can maximize big data in the cloud with Apache Hadoop. Download this eBook now. Brought to you in partnership with Hortonworks.

A few days ago I got a question regarding the automatic identifiers of documents in Solr 4.0, because the method from Solr 3 was deprecated. Because of that we decided to write a quick post about how to use Solr to generate documents unique identifier in Solr 4.x.

Data structure

Our simple data structure (fields section of the schema.xml file) looks as follows:

<fields>
 <field name="id" type="string" indexed="true" stored="true" required="true" multiValued="false" />
 <field name="name" type="text_general" indexed="true" stored="true"/>
 <field name="_version_" type="long" indexed="true" stored="true"/>
</fields>

In addition to that we’ve added the information about which field is the one that should contain unique identifiers. This was also done in schema.xml file:

<uniqueKey>id</uniqueKey>

Solr configuration

In addition to changes in the schema.xml file, we need to modify the solrconfig.xml file and introduce a proper UpdateRequestProcessorChain, like the following one:

<updateRequestProcessorChain>
 <processor class="solr.UUIDUpdateProcessorFactory">
  <str name="fieldName">id</str>
 </processor>
 <processor class="solr.LogUpdateProcessorFactory" />
 <processor class="solr.RunUpdateProcessorFactory" />
</updateRequestProcessorChain>

By doing this we inform Solr that we want the id field contents to be automatically generated.

A simple test

Let’s test what we did. In order to do that we will index a simple document by using the following command:

curl -XPOST 'localhost:8983/solr/update?commit=true' --data-binary '<add><doc><field name="name">Test</field></doc></add>' -H 'Content-type:application/xml'

If everything went well the above document was indexed. In order to check what happened we will send a simple query and look at the results. In order to do that we use the following comand:

curl -XGET 'localhost:8983/solr/select?q=*:*&indent=true'

The result returned by Solr for the above command is as follows:

<?xml version="1.0" encoding="UTF-8"?>
<response>
 <lst name="responseHeader">
  <int name="status">0</int>
  <int name="QTime">0</int>
  <lst name="params">
   <str name="indent">true</str>
   <str name="q">*:*</str>
  </lst>
 </lst>
 <result name="response" numFound="1" start="0">
  <doc>
   <str name="name">Test</str>
   <str name="id">1cdee8b4-c42d-4101-8301-4dc350a4d522</str>
   <long name="_version_">1439726523307261952</long>
  </doc>
 </result>
</response>

As we can see the unique identifier was automatically generated. Now if we would send the same indexing command once again:

curl -XPOST 'localhost:8983/solr/update?commit=true' --data-binary '<add><doc><field name="name">Test</field></doc></add>' -H 'Content-type:application/xml'

And run the same query again:

curl -XGET 'localhost:8983/solr/select?q=*:*&indent=true'

We would get two documents in results, just like the following:

<?xml version="1.0" encoding="UTF-8"?>
<response>
 <lst name="responseHeader">
  <int name="status">0</int>
  <int name="QTime">1</int>
  <lst name="params">
   <str name="indent">true</str>
   <str name="q">*:*</str>
  </lst>
 </lst>
 <result name="response" numFound="2" start="0">
  <doc>
   <str name="name">Test</str>
   <str name="id">1cdee8b4-c42d-4101-8301-4dc350a4d522</str>
   <long name="_version_">1439726523307261952</long>
  </doc>
  <doc>
   <str name="name">Test</str>
   <str name="id">9bedcb5f-1b71-4ab7-80a9-9882a6bf319e</str>
   <long name="_version_">1439726693819351040</long>
  </doc>
 </result>
</response>

As you can see, the two above documents have different unique identifiers, so the functionality works.

Hortonworks DataFlow is an integrated platform that makes data ingestion fast, easy, and secure. Download the white paper now.  Brought to you in partnership with Hortonworks

Topics:

Published at DZone with permission of Rafał Kuć, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

The best of DZone straight to your inbox.

SEE AN EXAMPLE
Please provide a valid email address.

Thanks for subscribing!

Awesome! Check your inbox to verify your email so you can start receiving the latest in tech news and resources.
Subscribe

{{ parent.title || parent.header.title}}

{{ parent.tldr }}

{{ parent.urlSource.name }}