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Lucene/Solr Synonym-Expanding EDisMax Parser Build Status

Current version : 5.0.5 (changelog)


Nolan Lawson

Health On the Net Foundation

Jan Høydahl


Apache 2.0.


Extension of the ExtendedDisMaxQueryParserPlugin that splits queries into a "normal" query and a "synonym" query. This enables proper query-time synonym expansion, with no reindexing required.

This also fixes lots of bugs with how Solr typically handles synonyms using the SynonymFilterFactory.

For more details, read my blog post on the subject.

Getting Started

The following tutorial will set up a working synonym-enabled Solr app using the techproducts sample project from Solr itself.

Step 1

Download the latest JAR file:

Or use Maven:

mvn dependency:copy -Dartifact=com.github.healthonnet:hon-lucene-synonyms:5.0.5 -DoutputDirectory=.

Or if you are using an older version of Solr, then you can use the last version of this plugin to support older Solr versions (1.3.5):

JAR Solr
hon-lucene-synonyms-1.3.5-solr-3.x.jar 3.4.0, 3.5.0, and 3.6.x
hon-lucene-synonyms-1.3.5-solr-4.0.0.jar 4.0.0
hon-lucene-synonyms-1.3.5-solr-4.1.0.jar 4.1.0 and 4.2.x
hon-lucene-synonyms-1.3.5-solr-4.3.0.jar 4.3+
hon-lucene-synonyms-2.0.0.jar 5.3.1

Step 2

Download Solr from the Solr home page. For this tutorial, we'll use Solr 6.2.0. You do not need the sources; the tgz or zip file will work fine.

Step 3

Extract the compressed file.

Step 4

Copy hon-lucene-synonyms-*.jar file into solr-6.2.0/server/solr-webapp/webapp/WEB-INF/lib/.

cp hon-lucene-synonyms-*.jar solr-6.2.0/server/solr-webapp/webapp/WEB-INF/lib/

Note that the jar may be placed in other locations if Solr is configured properly. The following tips are primarily valid only in Solr stand-alone and Solr Master/Slave configurations. The Solr Plugins section of the Solr CWIKI has more details about running plugins on Solr.

If you want to configure the plugin for SolrCloud check out Adding Custom Plugins in SolrCloud Mode.

Step 5

Download example_synonym_file.txt and copy it to the solr-6.2.0/server/solr/configsets/sample_techproducts_configs/conf/ directory.

Step 6

Download example_config.xml and copy the <queryParser>...</queryParser> section into solr-6.2.0/server/solr/configsets/sample_techproducts_configs/conf/solrconfig.xml just before the </config> tag at the end.

This defines the analyzer that will be used to generate synonyms.

Protip: You can customize this analyzer based on your synonym set. E.g. if your synonyms are all two words or less, you can safely set maxShingleSize to 2.

Step 7

Start up the app by running solr-6.2.0/bin/solr -e techproducts.

Step 8

In your browser, navigate to


You should see a response like this:

<lst name="debug">
  <str name="rawquerystring">dog</str>
  <str name="querystring">dog</str>
  <str name="parsedquery">(DisjunctionMaxQuery((text:dog))^1.0 ((+(DisjunctionMaxQuery((text:canis)) DisjunctionMaxQuery((text:familiaris))))/no_coord^1.0) ((+DisjunctionMaxQuery((text:hound)))/no_coord^1.0) ((+(DisjunctionMaxQuery((text:man's)) DisjunctionMaxQuery((text:best)) DisjunctionMaxQuery((text:friend))))/no_coord^1.0) ((+DisjunctionMaxQuery((text:pooch)))/no_coord^1.0))</str>
  <str name="parsedquery_toString">(((text:dog))^1.0 ((+((text:canis) (text:familiaris)))^1.0) ((+(text:hound))^1.0) ((+((text:man's) (text:best) (text:friend)))^1.0) ((+(text:pooch))^1.0))</str>
  <lst name="explain"/>
  <arr name="queryToHighlight">
    <str>^1.0 ((+((text:canis) (text:familiaris)))^1.0) ((+(text:hound))^1.0) ((+((text:man's) (text:best) (text:friend)))^1.0) ((+(text:pooch))^1.0)</str>
  <arr name="expandedSynonyms">
    <str>canis familiaris</str>
    <str>man's best friend</str>
  <lst name="mainQueryParser">
    <str name="QParser">ExtendedDismaxQParser</str>
    <null name="altquerystring"/>
    <null name="boost_queries"/>
    <arr name="parsed_boost_queries"/>
    <null name="boostfuncs"/>
  <lst name="synonymQueryParser">
    <str name="QParser">ExtendedDismaxQParser</str>
    <null name="altquerystring"/>
    <null name="boost_queries"/>
    <arr name="parsed_boost_queries"/>
    <null name="boostfuncs"/>

Note that the input query dog has been expanded into dog, hound, pooch, canis familiaris, and man's best friend.

Tweaking the results

Boost the non-synonym part to 1.2 and the synonym part to 1.1 by adding synonyms.originalBoost=1.2&synonyms.synonymBoost=1.1:

((+((text:canis) (text:familiaris)))^1.1) 
((+((text:man's) (text:best) (text:friend)))^1.1) 

Apply a minimum "should" match of 75% by adding mm=75%25:

((+(((text:canis) (text:familiaris))~1))^1.0) 
((+(((text:man's) (text:best) (text:friend))~2))^1.0) 

Observe how phrase queries are properly handled by using q="dog" instead of q=dog:

((+(text:"canis familiaris"))^1.0) 
((+(text:"man's best friend"))^1.0) 


Keep in mind that you must add defType=synonym_edismax and synonyms=true to enable the parser in the first place.

Also, you must either define qf in the query parameters or defaultSearchField in solr/conf/schema.xml, so that the parser knows which fields to use during synonym expansion.

If you enable debugging (with debugQuery=on), the plugin will output helpful information about how synonyms are being expanded.

Query parameters

The following are parameters that you can use to tweak the synonym expansion.

Param Type Default Summary
synonyms boolean false Enable or disable synonym expansion entirely. True if enabled.
synonyms.analyzer String null Name of the analyzer defined in solrconfig.xml to use. (E.g. in the examples, it's myCoolAnalyzer). This must be non-null, if you define more than one analyzer (e.g. for more than one language).
synonyms.originalBoost float 1.0 Boost value applied to the original (non-synonym) part of the query.
synonyms.synonymBoost float 1.0 Boost value applied to the synonym part of the query.
synonyms.disablePhraseQueries boolean false True if synonym expansion should be disabled when the user input contains a phrase query (i.e. a quoted query). This option is offered because expansion of phrase queries may be considered non-intuitive to users.
synonyms.constructPhrases boolean false v1.2.2+: True if expanded synonyms should always be treated like phrases (i.e. wrapped in quotes). This option is offered in case your synonyms contain lots of phrases composed of common words (e.g. "man's best friend" for "dog"). Only affects the expanded synonyms; not the original query. See issue #5 for more discussion.
synonyms.ignoreQueryOperators boolean false v1.3.2+: If you treat query operators (e.g. AND and OR) as usual words and want the synonyms be added to the query anyhow, set this option to true.
synonyms.bag boolean false v1.3.2+: When false (default), this plugin generates additional synonym queries by using the original query string as a template: dog bite => dog bite, canis familiaris bite, dog chomp, canis familiaris chomp. When true a simpler, "bag of terms" query is created from the synonyms. IE dog bite => bite dog chomp canis familiaris. The simpler query will be more performant but loses positional information. Use with synonyms.constructPhrases to keep synonym phrases such as "canis familiaris".
synonyms.ignoreMM boolean false v1.3.5+: When false (default), the mm param is applied to the original query and to the synonym queries. When true mm is ignored for the synonym queries and applied only to the original query.

Compile it yourself

Download the code and run:

mvn install


Run the tests using maven:

mvn test


  • 5.0.5
    • Tested with Solr 6.2.0
    • Fixed #65 Matches all docs if bf (Boost Function) present @janhoy
  • 5.0.4
    • Solr 6.0.0 support.
    • Distributed on Maven central now.
  • 2.0.0
    • BREAKING CHANGE: Updated to support Solr 5.3.1. Removed support for older versions of Solr.
    • Note that as of Lucene 5.2.0, when synonyms are parsed, original terms are now correctly marked as type word instead of type synonym LUCENE-6400.
  • v1.3.5
    • Added synonyms.ignoreMM option
  • v1.3.4
  • v1.3.3
    • Fixed #33: synonyms are now weighted equally, regardless of how many there are per word.
    • Fixed #31: synonyms are no longer given extra weight when using the params bq, bf, and boost.
    • debugQuery=on now gives more helpful debug output.
    • Fixed #9, #26, #32, and #34. Note that this is a documentation change; not a code change, so to get the benefits of this "fix," you'll need to manually perform Step 6 again.
  • v1.3.2
    • Added synonyms.ignoreQueryOperators option (#28)
    • Added synonyms.bag option (#30)
    • The script now downloads the proper version of Solr.
  • v1.3.1
    • Avoid luceneMatchVersion in config (#20)
  • v1.3.0
    • Added support for Solr 4.3.0 (#19)
    • New way of loading Tokenizers and TokenFilters
    • New XML syntax for config in solrconfig.xml
  • v1.2.3
    • Fixed #16
    • Verified support for Solr 4.2.0 with the 4.1.0 branch (unit tests passed)
    • Improved automation of unit tests
  • v1.2.2
    • Added synonyms.constructPhrases option to fix #5
    • Added proper handling for phrase slop settings
  • v1.2.1
    • Added support for Solr 4.1.0 (#4)
  • v1.2
    • Added support for Solr 4.0.0 (#3)
  • v1.1
    • Added support for Solr 3.6.1 and 3.6.2 (#1)
    • Added "Getting Started" instructions to clarify plugin usage (#2)
  • v1.0
    • Initial release