Search code examples
solrlucenefull-text-searchedismaxdismax

Solr - mm paramter of dismax parser

I am using Solr 5.2.1, in one of my project, and got some doubt on mm paramter of dismax / edismax parser.

Questions:

  • Does mm regardless of total input term count? Document says yes, but when I set it to 3, and input a single term, it still could get records, so it seems not regardless of total input term count.
  • What is the default value of mm? Document says it's 100%, but in my query test, it seems to be 1. By the way, I didn't found configuration for mm in solrconfig.xml or schema.xml.

Any help? Thx.

@Update:

Query url for 1st question:

http://localhost:8983/solr/demo/select?q=new+york&start=0&wt=json&indent=true&defType=edismax&qf=title&mm=3&stopwords=true&lowercaseOperators=true

There are 2 terms new and york, the query result is:

  • don't specify mm, return 3 records,
  • mm = 2, return 1 records,
  • mm = 3, also return 1 records,

So, I guess it will change the mm to max term first, before query.

Solution

  • Answer-2: If no mm parameter is specified in the query, or as a default in solrconfig.xml, the effective value of the q.op parameter (either in the query, as a default in solrconfig.xml, or from the 'defaultOperator' option in schema.xml) is used to influence the behavior. So the default behavior of the mm is determined by q.op parameter. If q.op is effectively AND, then mm=100%; if q.op is OR, then mm=1.