1. 简述

Filter查询时不计算相关性的，同时可以进行缓存，因此，Filter查询的速度要快于query查询；

2. 数据准备

POST /lib9/items/_bulk
{"index": {"id": 1}}
{"price": 40,"itemID": "ID100123"}
{"index": {"_id": 2}}
{"price": 50,"itemID": "ID100124"}
{"index": {"_id": 3}}
{"price": 25,"itemID": "ID100124"}
{"index": {"_id": 4}}
{"price": 30,"itemID": "ID100125"}
{"index": {"_id": 5}}
{"price": null,"itemID": "ID100127"}

3. filter查询

3.1 简单过滤查询

# 查询price=40的文档
GET /lib9/items/_search
{
  "post_filter": {
    "term": {
      "price": 40
    }
  }
}
# 查询price等于25或40的文档
GET /lib9/items/_search
{
  "post_filter": {
    "terms": {
      "price": [
        25,
        40
      ]
    }
  }
}
# 查询itemID等于ID100123的文档(注意在这里要写成小写id)
GET /lib9/items/_search
{
  "post_filter": {
    "term": {
      "itemID": "id100123"
    }
  }
}

3.2 bool过滤查询

可以实现组合过滤查询

# 格式
{
    "bool": {
        "must": [],
        "should": [],
        "must_not": []
    }
}

注意
**1. must：必须要满足的条件 —and

should：可以满足也可以不满足的条件 —or

must_not：不需要满足的条件 —not**

GET /lib9/items/_search
{
“post_filter”: {

 "bool": {
   "should": [
     {
       "term": {
         "price": 25
       }
     },
     {
       "term": {
         "itemID": "id100123"
       }
     }
   ],
   "must_not": [
     {
       "term": {
         "price": 30
       }
     }
   ]
 }

}
}

GET /lib9/items/_search
{
“post_filter”: {

 "bool": {
   "should": [
     {
       "term": {
         "itemID": "id100123"
       }
     },
     {
       "bool": {
         "must": [
           {
             "term": {
               "itemID": "id100124"
             }
           },
           {
             "term": {
               "price": 40
             }
           }
         ]
       }
     }
   ]
 }

}
}

3.3 range范围过滤

gt：>
lt：<
gte：>=
lte：<=

GET /lib9/items/_search
{
  "post_filter": {
    "range": {
      "price": {
        "gt": 35,
        "lt": 50
      }
    }
  }
}

3.4 过滤非空

GET /lib9/items/_search
{
  "query": {
    "bool": {
      "filter": {
        "exists": {
          "field": "price"
        }
      }
    }
  }
}
GET /lib9/items/_search
{
  "query": {
    "constant_score": {
      "filter": {
        "exists": {
          "field": "price"
        }
      }
    }
  }
}

3.5 过滤器缓存

ElasticSearch有一种特殊的缓存，即过滤器缓存(filter cache)，用来存储过滤器的结果，被缓存的过滤器并不需要消耗过多的内存，而且可供后续所有与之相关的查询重复使用，从而极大地提高了查询性能。
注意：ElasticSearch并不是默认缓存所有过滤器，

以下过滤器默认不缓存：

numeric_range
script
geo_bbox
geo_distance
geo_distance_range
geo_polygon
geo_shape
and
or
not
以下过滤器默认开启缓存

exists
missing
range
term
terms
开启方式：在filter查询语句后边加上 “_catch”:true

4. 聚合查询

sum

GET /lib9/items/_search
{
“size”:0,
“aggs”: {

 "price_of_sum": {
     "sum": {
       "field": "price"
     }
 }

}
}

运行结果

{
  "took": 6,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 5,
    "max_score": 0,
    "hits": []
  },
  "aggregations": {
    "price_of_sum": {
      "value": 160
    }
  }
}

min

GET /lib9/items/_search
{
“size”: 0,
“aggs”: {

"price_of_min": {
  "min": {
    "field": "price"
  }
}

}
}

运行结果

{
  "took": 4,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 5,
    "max_score": 0,
    "hits": []
  },
  "aggregations": {
    "price_of_min": {
      "value": 30
    }
  }
}