Apache Solr

Apache Solr Multilingual Search: Language Identification Example

This is an article related to the Apache Solr Multilingual Search: Language Identification. Generally, Apache Solr is used for search and browsing categories and facets.

1. Introduction

Apache Solr is an open-source software java search engine. It is scalable and can process a high volume of data. It is used to index the content and search a huge amount of content. It is a popular search engine. It is used as a document-based NoSQL data source. It can be also used as a key-value store. Solr has JSON, XML, and HTTP REST API.

2.1 Prerequisites

Java 7 or 8 is required on the Linux, windows, or Mac operating system. Apache Solr 4.7.0 is required for this example.

2.2 Download

You can download Java 8 can be downloaded from the Oracle website. Apache Solr’s latest releases are available from the Apache Solr website.

2.3 Setup

You can set the environment variables for JAVA_HOME and PATH. They can be set as shown below:


export JAVA_HOME
export PATH

2.4 How to download and install Apache Solr

Apache Solr’s latest releases are available from the Apache Solr website. After downloading the zip file can be extracted to a folder.

To start the Apache Solr, you can use the command below:

Solr start command

bin/solr start

The output of the above command is shown below:

Solr start command output

apples-MacBook-Air:solr-8.8.2 bhagvan.kommadi$ bin/solr start
*** [WARN] *** Your open file limit is currently 2560.  
 It should be set to 65000 to avoid operational disruption. 
 If you no longer wish to see this warning, set SOLR_ULIMIT_CHECKS to false in your profile or solr.in.sh
*** [WARN] ***  Your Max Processes Limit is currently 1392. 
 It should be set to 65000 to avoid operational disruption. 
 If you no longer wish to see this warning, set SOLR_ULIMIT_CHECKS to false in your profile or solr.in.sh
Waiting up to 180 seconds to see Solr running on port 8983 [-]  
Started Solr server on port 8983 (pid=3054). Happy searching!

You can access the Solr application from the browse at : http://localhost:8983/solr/. The screenshot below shows the Solr application.

solr language identification - solr app
Solr Application

2.5 Apache Solr

Apache Solr merged into Lucene around 2010. Lucene was created by Doug Cutting in 1999. Solr was developed by Yonik Seeley at CNET. Solr had a cloud feature released in 4.0. Solr 6.0 supported parallel SQL queries. Solr is based on Lucene. It has REST API support. It has an inverted index feature to get documents for a query using the search word. The search word is entered by the user to link the documents to the word. Solr has the features such as support for XML/JSON/HTTP, recommendations, automatic load balancing, spell suggestions, autocompletion, geospatial search, authentication, authorization, multilingual keyword search, type ahead prediction, batch processing, streaming, machine learning models, high volume web traffic support, schema, schemaless configuration, faceted search, filtering, and cluster configuration.

2.6 Apache Solr – Language Identification Example

To handle multiple languages, a field per language approach can be used in Apache Solr. Solr supports different languages. We need to set up the schema to search across three languages: English, Spanish, and French.

First, let us look at the configuration of language identification to find the language of a document.

solr configuration

<?xml version="1.0" encoding="UTF-8" ?>
  <!-- Begin everything else -->
	<lib dir="../../../contrib/langid/lib/" />
	   <lib dir="../../../dist/" regex="solr-langid-\d.*\.jar" />

       <directoryFactory name="DirectoryFactory"

       <updateHandler class="solr.DirectUpdateHandler2">
           <str name="dir">${solr.ulog.dir:}</str>

       <requestDispatcher handleSelect="false" >
           <httpCaching never304="true" />

       <requestHandler name="/select" class="solr.SearchHandler">
           <lst name="defaults">
               <str name="echoParams">none</str>
               <str name="df">content</str>
               <str name="wt">json</str>
               <str name="indent">true</str>

       <updateRequestProcessorChain name="langid">
         <processor class="org.apache.solr.update.processor.LangDetectLanguageIdentifierUpdateProcessorFactory">
           <lst name="invariants">
             <str name="langid.fl">content,content_lang1,content_lang2,content_lang3</str>
             <str name="langid.langField">language</str>
             <str name="langid.langsField">languages</str>
             <str name="langid.map">true</str>
             <str name="langid.map.individual">true</str>
             <str name="langid.map.fl">content_lang1,content_lang2,content_lang3</str>str>
             <str name="langid.whitelist">en,es,fr</str>
             <str name="langid.map.lcmap">en:english es:spanish fr:french</str>
         <processor class="solr.LogUpdateProcessorFactory" />
         <processor class="solr.RunUpdateProcessorFactory" />

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

       <queryResponseWriter name="json" class="solr.JSONResponseWriter">
           <str name="content-type">text/plain; charset=UTF-8</str>



Let us look at a schema to support the above three languages.

schema file

<?xml version="1.0" encoding="UTF-8" ?>
<schema name="example" version="1.5">
      <fieldType name="text_english" class="solr.TextField" positionIncrementGap="100">
              <tokenizer class="solr.StandardTokenizerFactory"/>
              <filter class="solr.StopFilterFactory"
              <filter class="solr.LowerCaseFilterFactory"/>
              <filter class="solr.EnglishPossessiveFilterFactory"/>
              <filter class="solr.KeywordMarkerFilterFactory" protected="protwords.txt"/>
              <filter class="solr.KStemFilterFactory"/>
      <fieldType name="text_spanish" class="solr.TextField" positionIncrementGap="100">
              <tokenizer class="solr.StandardTokenizerFactory"/>
              <filter class="solr.LowerCaseFilterFactory"/>
              <filter class="solr.StopFilterFactory" ignoreCase="true" words="lang/stopwords_es.txt" format="snowball"/>
              <filter class="solr.SpanishLightStemFilterFactory"/>
      <fieldType name="text_french" class="solr.TextField" positionIncrementGap="100">
              <tokenizer class="solr.StandardTokenizerFactory"/>
              <filter class="solr.ElisionFilterFactory" ignoreCase="true" articles="lang/contractions_fr.txt"/>
              <filter class="solr.LowerCaseFilterFactory"/>
              <filter class="solr.StopFilterFactory" ignoreCase="true" words="lang/stopwords_fr.txt" format="snowball"/>
              <filter class="solr.FrenchLightStemFilterFactory"/>
      <fieldType name="text_general" class="solr.TextField" positionIncrementGap="100">
          <analyzer type="index">
              <tokenizer class="solr.StandardTokenizerFactory"/>
              <filter class="solr.StopFilterFactory" ignoreCase="true" words="stopwords.txt" />
              <filter class="solr.LowerCaseFilterFactory"/>
          <analyzer type="query">
              <tokenizer class="solr.StandardTokenizerFactory"/>
              <filter class="solr.StopFilterFactory" ignoreCase="true" words="stopwords.txt" />
              <filter class="solr.SynonymFilterFactory" synonyms="synonyms.txt" ignoreCase="true" expand="true"/>
              <filter class="solr.LowerCaseFilterFactory"/>
      <fieldType name="string" class="solr.StrField" sortMissingLast="true" />
      <fieldType name="long" class="solr.TrieLongField" precisionStep="0" positionIncrementGap="0"/>


    <field name="id" type="string" indexed="true" stored="true" />
    <field name="_version_" type="long" indexed="true" stored="true"/>
    <field name="text" type="string" indexed="true" stored="false" multiValued="true"/>
    <field name="title" type="string" indexed="true" stored="true" />
    <field name="content" type="string" indexed="false" stored="false" />
    <field name="content_lang1" type="string" indexed="false" stored="false" />
    <field name="content_lang2" type="string" indexed="false" stored="false" />
    <field name="content_lang3" type="string" indexed="false" stored="false" />
    <field name="language"  type="string"  indexed="true"  stored="true" />
    <field name="languages" type="string"  indexed="true"  stored="true" multiValued="true"/>
    <dynamicField name="*_english"  type="text_english" indexed="true"  stored="true" multiValued="true"/>
    <dynamicField name="*_spanish"  type="text_spanish" indexed="true"  stored="true" multiValued="true"/>
    <dynamicField name="*_french"  type="text_french" indexed="true"  stored="true" multiValued="true"/>



You can implement this by copying the directory example within solr installation and rename it as langdetect. Ensure that it is a deep copy of the directory. Within the directory, remove the unused directories like example-DIH, multicore,and example-schemaless. Remove the directories under the solr folder except for bin. You can copy the folders and files from the source code ($SOURCE_CODE) provided to solr. You can execute the commands below from the langdetect directory

Solr initial setup

cp -R example langdetect
cd langdetect
rm -r example-DIH
rm -r multicore
cd solr
rm -r collection1
cp * $SOURCE_CODE/* .

Note that the core.properties is changed the name from collection to langdetect directory. You can restart Solr from langdetect folder by using the command below:

Solr start command

cd $SOLR_INSTALL/langdetect
java -jar start.jar

The output of the command is shown below:

Solr start output

apples-MacBook-Air:languagedetection bhagvan.kommadi$ java -jar start.jar 
0    [main] INFO  org.eclipse.jetty.server.Server  – jetty-8.1.10.v20130312
42   [main] INFO  org.eclipse.jetty.deploy.providers.ScanningAppProvider  – Deployment monitor /Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/contexts at interval 0
53   [main] INFO  org.eclipse.jetty.deploy.DeploymentManager  – Deployable added: /Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/contexts/solr-jetty-context.xml
1414 [main] INFO  org.eclipse.jetty.webapp.StandardDescriptorProcessor  – NO JSP Support for /solr, did not find org.apache.jasper.servlet.JspServlet
1494 [main] INFO  org.apache.solr.servlet.SolrDispatchFilter  – SolrDispatchFilter.init()
1518 [main] INFO  org.apache.solr.core.SolrResourceLoader  – JNDI not configured for solr (NoInitialContextEx)
1519 [main] INFO  org.apache.solr.core.SolrResourceLoader  – solr home defaulted to 'solr/' (could not find system property or JNDI)
1522 [main] INFO  org.apache.solr.core.SolrResourceLoader  – new SolrResourceLoader for directory: 'solr/'
1667 [main] INFO  org.apache.solr.core.ConfigSolr  – Loading container configuration from /Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/solr.xml
1900 [main] INFO  org.apache.solr.core.CoresLocator  – Config-defined core root directory: /Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr
1915 [main] INFO  org.apache.solr.core.CoreContainer  – New CoreContainer 1720339
1916 [main] INFO  org.apache.solr.core.CoreContainer  – Loading cores into CoreContainer [instanceDir=solr/]
1935 [main] INFO  org.apache.solr.handler.component.HttpShardHandlerFactory  – Setting socketTimeout to: 0
1935 [main] INFO  org.apache.solr.handler.component.HttpShardHandlerFactory  – Setting urlScheme to: null
1942 [main] INFO  org.apache.solr.handler.component.HttpShardHandlerFactory  – Setting connTimeout to: 0
1943 [main] INFO  org.apache.solr.handler.component.HttpShardHandlerFactory  – Setting maxConnectionsPerHost to: 20
1947 [main] INFO  org.apache.solr.handler.component.HttpShardHandlerFactory  – Setting corePoolSize to: 0
1948 [main] INFO  org.apache.solr.handler.component.HttpShardHandlerFactory  – Setting maximumPoolSize to: 2147483647
1949 [main] INFO  org.apache.solr.handler.component.HttpShardHandlerFactory  – Setting maxThreadIdleTime to: 5
1949 [main] INFO  org.apache.solr.handler.component.HttpShardHandlerFactory  – Setting sizeOfQueue to: -1
1950 [main] INFO  org.apache.solr.handler.component.HttpShardHandlerFactory  – Setting fairnessPolicy to: false
2250 [main] INFO  org.apache.solr.logging.LogWatcher  – SLF4J impl is org.slf4j.impl.Log4jLoggerFactory
2251 [main] INFO  org.apache.solr.logging.LogWatcher  – Registering Log Listener [Log4j (org.slf4j.impl.Log4jLoggerFactory)]
2252 [main] INFO  org.apache.solr.core.CoreContainer  – Host Name: 
2460 [main] INFO  org.apache.solr.core.CoresLocator  – Looking for core definitions underneath /Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr
2472 [main] INFO  org.apache.solr.core.CoresLocator  – Found core langdetect in /Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/langdetect/
2473 [main] INFO  org.apache.solr.core.CoresLocator  – Found 1 core definitions
2476 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.CoreContainer  – Creating SolrCore 'langdetect' using instanceDir: /Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/langdetect
2476 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrResourceLoader  – new SolrResourceLoader for directory: '/Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/langdetect/'
2511 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrConfig  – Adding specified lib dirs to ClassLoader
2513 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrResourceLoader  – Adding 'file:/Users/bhagvan.kommadi/Desktop/solr-4.7.0/contrib/langid/lib/jsonic-1.2.7.jar' to classloader
2514 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrResourceLoader  – Adding 'file:/Users/bhagvan.kommadi/Desktop/solr-4.7.0/contrib/langid/lib/langdetect-1.1-20120112.jar' to classloader
2517 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrResourceLoader  – Adding 'file:/Users/bhagvan.kommadi/Desktop/solr-4.7.0/dist/solr-langid-4.7.0.jar' to classloader
2547 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrConfig  – Using Lucene MatchVersion: LUCENE_47
2698 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.Config  – Loaded SolrConfig: solrconfig.xml
2707 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.schema.IndexSchema  – Reading Solr Schema from schema.xml
2725 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.schema.IndexSchema  – [langdetect] Schema name=example
2790 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.schema.IndexSchema  – default search field in schema is text
2791 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.schema.IndexSchema  – unique key field: id
2925 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – solr.NRTCachingDirectoryFactory
2931 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – [langdetect] Opening new SolrCore at /Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/langdetect/, dataDir=/Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/langdetect/data/
2931 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – JMX monitoring not detected for core: langdetect
2943 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.CachingDirectoryFactory  – return new directory for /Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/langdetect/data
2943 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – New index directory detected: old=null new=/Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/langdetect/data/index/
2944 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.CachingDirectoryFactory  – return new directory for /Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/langdetect/data/index
2955 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – created json: solr.JSONResponseWriter
3023 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.update.processor.UpdateRequestProcessorChain  – creating updateRequestProcessorChain "langid"
3674 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.update.processor.UpdateRequestProcessorChain  – inserting DistributedUpdateProcessorFactory into updateRequestProcessorChain "langid"
3674 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – no updateRequestProcessorChain defined as default, creating implicit default
3680 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.RequestHandlers  – created /select: solr.SearchHandler
3683 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.RequestHandlers  – created /update: solr.UpdateRequestHandler
3709 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.handler.loader.XMLLoader  – xsltCacheLifetimeSeconds=60
3767 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – Hard AutoCommit: if uncommited for 15000ms; 
3768 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – Soft AutoCommit: disabled
3819 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – SolrDeletionPolicy.onInit: commits: num=1
	commit{dir=NRTCachingDirectory(NIOFSDirectory@/Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/langdetect/data/index lockFactory=NativeFSLockFactory@/Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection/solr/langdetect/data/index; maxCacheMB=48.0 maxMergeSizeMB=4.0),segFN=segments_4,generation=4}
3821 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.SolrCore  – newest commit generation = 4
3859 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.search.SolrIndexSearcher  – Opening Searcher@12a34218[langdetect] main
3869 [searcherExecutor-5-thread-1] INFO  org.apache.solr.core.SolrCore  – [langdetect] Registered new searcher Searcher@12a34218[langdetect] main{StandardDirectoryReader(segments_4:11:nrt _2(4.7):C4)}
3870 [coreLoadExecutor-4-thread-1] INFO  org.apache.solr.core.CoreContainer  – registering core: langdetect
3874 [main] INFO  org.apache.solr.servlet.SolrDispatchFilter  – user.dir=/Users/bhagvan.kommadi/Desktop/solr-4.7.0/languagedetection
3875 [main] INFO  org.apache.solr.servlet.SolrDispatchFilter  – SolrDispatchFilter.init() done
3920 [main] INFO  org.eclipse.jetty.server.AbstractConnector  – Started SocketConnector@ 

You can post the multilanguage file (provided in the source code) from $SOLR_INSTALL/example-docs using the command below.

posting multilanguage files to solr

apples-MacBook-Air:exampledocs bhagvan.kommadi$ java -Durl=http://localhost:8983/solr/langdetect/update -jar post.jar /Users/bhagvan.kommadi/desktop/JavacodeGeeks/code/apachesollangidentification/multi_lang.xml 
SimplePostTool version 1.5
Posting files to base url http://localhost:8983/solr/langdetect/update using content-type application/xml..
POSTing file multi_lang.xml
1 files indexed.
COMMITting Solr index changes to http://localhost:8983/solr/langdetect/update..
Time spent: 0:00:00.491

You can launch the browser pointing to http://localhost:8983/solr/. The screenshot below shows the query results in langdetect core.

Language Detection: Query results

3. Download the Source Code

You can download the full source code of this example here: Apache Solr Multilingual Search: Language Identification Example

Bhagvan Kommadi

Bhagvan Kommadi is the Founder of Architect Corner & has around 20 years’ experience in the industry, ranging from large scale enterprise development to helping incubate software product start-ups. He has done Masters in Industrial Systems Engineering at Georgia Institute of Technology (1997) and Bachelors in Aerospace Engineering from Indian Institute of Technology, Madras (1993). He is member of IFX forum,Oracle JCP and participant in Java Community Process. He founded Quantica Computacao, the first quantum computing startup in India. Markets and Markets have positioned Quantica Computacao in ‘Emerging Companies’ section of Quantum Computing quadrants. Bhagvan has engineered and developed simulators and tools in the area of quantum technology using IBM Q, Microsoft Q# and Google QScript. He has reviewed the Manning book titled : "Machine Learning with TensorFlow”. He is also the author of Packt Publishing book - "Hands-On Data Structures and Algorithms with Go".He is member of IFX forum,Oracle JCP and participant in Java Community Process. He is member of the MIT Technology Review Global Panel.
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