Elasticsearch: should + minimum_should_match vs must

Question

I test with these 2 queries

Query with must

 {
  "size": 200,
  "from": 0,
  "query": {
  "bool": {
  "must": [ {
      "match": {
        "_all": "science"
      }
    },
    {
      "match": {
        "category": "fiction"
      }
    },
    {
      "match": {
        "country": "us"
      }
    }
   ]
 }
}

}

Query with should + minimum_should_match

  {
   "size": 200,
   "from": 0,
   "query": {
   "bool": {
   "should": [ {
       "match": {
         "_all": "science"
       }
     },
     {
      "match": {
        "category": "fiction"
        }
      },
      {
      "match": {
        "country": "us"
        }
      }
    ],
     minimum_should_match: 3
  }
 }
}

Both queries give me same result, I don't know the difference between these 2, when we should use minimum_should_match?

Answer 1

I guess you mean minimum_number_should_match, right?

In both cases it would be the same because you have the same number of clauses in should. minimum_number_should_match usually is used when you have more clauses than the number you specify there.

For example if you have 5 should clauses, but for some reason you only need three of them to be fulfilled you would do something like this:

{
  "query": {
    "bool": {
      "should": [
        {
          "term": {
            "tag": "wow"
          }
        },
        {
          "term": {
            "tag": "elasticsearch"
          }
        },
        {
          "term": {
            "tag": "tech"
          }
        },
        {
          "term": {
            "user": "plchia"
          }
        },
        {
          "range": {
            "age": {
              "gte": 10,
              "lte": 20
            }
          }
        }
      ],
      "minimum_should_match": 3
    }
  }
}