Usage example of Function Score Query to control search relevancy.

function_score-query-example.js

##################################################
# Function Score Query Example
##################################################
# Note: `now` should be replaced by `2018-12-06` for expected results

# Prepare for items index

DELETE items

PUT items
{
  "mappings": {
    "doc": {
      "properties": {
        "origin": {
          "properties": {
            "location": {
              "type": "geo_point"
            },
            "prefecture": {
              "type": "keyword"
            }
          }
        },
        "price": {
          "type": "long"
        },
        "name": {
          "type": "text",
            "fields" : {
              "keyword" : {
                "type" : "keyword",
                "ignore_above" : 256
              }
            }
        },
        "promotion": {
          "type": "long"
        },
        "arrival_date": {
          "type": "date"
        }
      }
    }
  },
  "settings": {
    "index": {
      "number_of_shards": "1",
      "number_of_replicas": "0"
    }
  }
}

POST items/doc/_bulk
{"index":{}}
{"arrival_date":"2018-12-02","name":"Tsugaru Apple","origin":{"prefecture":"Aomori","location":"40.82,140.73"},"price":310,"promotion":2}
{"index":{}}
{"arrival_date":"2018-11-29","name":"Shinano Apple","origin":{"prefecture":"Nagano","location":"36.65,138.17"},"price":280,"promotion":10}
{"index":{}}
{"arrival_date":"2018-12-04","name":"Fuji Apple","origin":{"prefecture":"Akita","location":"39.69,139.78"},"price":150,"promotion":1}
{"index":{}}
{"arrival_date":"2018-12-04","name":"Mikkabi Mandarine Orange","origin":{"prefecture":"Shizuoka","location":"34.97,138.38"},"price":80,"promotion":1}

# Show Apples Only

GET items/_search
{
  "profile": "true", 
  "query": {
    "match": {
      "name": "apple"
    }
  }
}

# Use function_score query instead

GET items/_search
{
  "query": {
    "function_score": {
      "query": {
        "match": {
          "name": "apple"
        }
      }
    }
  }
}

# Bias the score by arrival_date (datetime)

GET items/_search
{
  "query": {
    "function_score": {
      "query": {
        "match": {
          "name": "apple"
        }
      },
      "linear": {
        "arrival_date": {
          "origin": "now",
          "scale": "7d",
          "offset": "0d"
        }
      }
    }
  }
}

# Bias the score by promotion (number)

GET items/_search
{
  "query": {
    "function_score": {
      "score_mode": "sum",
      "query": {
        "match": {
          "name": "apple"
        }
      },
      "linear": {
        "promotion": {
          "origin": "10",
          "scale": "10",
          "offset": "0"
        }
      }
    }
  }
}

# Bias the score by location (geo distance)

GET items/_search
{
  "query": {
    "function_score": {
      "score_mode": "sum",
      "query": {
        "match": {
          "name": "apple"
        }
      },
      "linear": {
        "origin.location": {
          "origin": "35.68,139.69",
          "offset": "0", 
          "scale": "300km"
        }
      }
    }
  }
}

# Bias the score by arrival_date + promotion

GET items/_search
{
  "profile": true,
  "query": {
    "function_score": {
      "score_mode": "sum",
      "query": {
        "match": {
          "name": "apple"
        }
      },
      "functions": [
        {
          "linear": {
            "arrival_date": {
              "origin": "now",
              "scale": "7d",
              "offset": "0d"
            }
          }
        },
        {
          "linear": {
            "promotion": {
              "origin": "10",
              "scale": "10",
              "offset": "0"
            }
          }
        }
      ]
    }
  }
}


# Using script_score instead **make sure which query consts more**

GET items/_search/
{
  "profile": true,
  "query": {
    "function_score": {
      "score_mode": "sum",
      "query": {
        "match": {
          "name": "apple"
        }
      },
      "script_score": {
        "script": "doc['promotion'].value - (new Date().getTime() - doc['arrival_date'].value.toInstant().toEpochMilli()) / 1000000 / 60"
      }
    }
  }
}