4.(过滤查询)Filter Query.md · 独孤先生/lgj-elasticsearch

# (过滤查询) Filter Query
## 过滤查询
    查询(query)即是之前提到的query查询，它 (查询)默认会计算每个返回文档的得分，然后根据得分排序
    过滤(filter)只会筛选出符合的文档，并不计算得分，且它可以缓存文档 
    换句话说，过滤适合在大范围筛选数据，而查询则适合精确匹配数据。一般应用时， 应先使用过滤操作过滤数据， 然后使用查询匹配数据
## 过滤语法
    GET /ems/emp/_search
    {
      "query": {
        "bool": {
          "must": [
            {"match_all": {}}
          ],
          "filter": {
            "range": {
              "age": {
                "gte": 10
              }
            }
          }
        }
      }
    }
    --------------------------------
    返回结果：
    {
        "took": 4, 
        "timed_out": false, 
        "_shards": {
            "total": 5, 
            "successful": 5, 
            "skipped": 0, 
            "failed": 0
        }, 
        "hits": {
            "total": 3, 
            "max_score": 1, 
            "hits": [
                {
                    "_index": "ems", 
                    "_type": "emp", 
                    "_id": "AXmw8VHfJwC9j-D14eQ_", 
                    "_score": 1, 
                    "_source": {
                        "name": "梅超风", 
                        "age": 43, 
                        "bir": "2012-12-12", 
                        "content": "Redis是一个开源的使用ANSI C语言编写、支持网络、可基于内存亦可持久化的日志型、Key-Value数据库，并提供多种语言的API", 
                        "address": "杭州"
                    }
                }, 
                {
                    "_index": "ems", 
                    "_type": "emp", 
                    "_id": "AXmw8VHfJwC9j-D14eQ7", 
                    "_score": 1, 
                    "_source": {
                        "name": "小黑", 
                        "age": 23, 
                        "bir": "2012-12-12", 
                        "content": "为开发团队选择一款优秀的MVC框架是件难事儿，在众多可行的方案中决择需要很高的经验和水平", 
                        "address": "北京"
                    }
                }, 
                {
                    "_index": "ems", 
                    "_type": "emp", 
                    "_id": "AXmw8VHfJwC9j-D14eQ8", 
                    "_score": 1, 
                    "_source": {
                        "name": "王小黑", 
                        "age": 24, 
                        "bir": "2012-12-12", 
                        "content": "Spring 框架是一个分层架构，由 7 个定义良好的模块组成。Spring 模块构建在核心容器之上，核心容器定义了创建、配置和管理 bean 的方式", 
                        "address": "上海"
                    }
                }
            ]
        }
    }
    
    在执行filter和query时,先执行filter在执行query{}
    Elasticsearch会自动缓存经常使用的过滤器，以加快性能
## 常见的过滤器类型
### term 、 terms
    含义与查询时一致，term用于精确匹配，terms用于多词条匹配，过滤上使用没有很大区别
    GET /ems/emp/_search   # 使用term过滤
    {
      "query": {
        "bool": {
          "must": [
            {"term": {
              "name": {
                "value": "小黑"
              }
            }}
          ],
          "filter": {
            "term": {
              "content":"spring"
            }
          }
        }
      }
    }
    --------------------------------
    返回结果：
    {
        "took": 1, 
        "timed_out": false, 
        "_shards": {
            "total": 5, 
            "successful": 5, 
            "skipped": 0, 
            "failed": 0
        }, 
        "hits": {
            "total": 0, 
            "max_score": null, 
            "hits": [ ]
        }
    }
    
    GET /ems/emp/_search  #使用terms过滤
    {
      "query": {
        "bool": {
          "must": [
            {"term": {
              "name": {
                "value": "梅超风"
              }
            }}
          ],
          "filter": {
            "terms": {
              "content":[
                  "redis",
                  "开源"
                ]
            }
          }
        }
      }
    }
    --------------------------------
    返回结果：
    {
        "took": 2, 
        "timed_out": false, 
        "_shards": {
            "total": 5, 
            "successful": 5, 
            "skipped": 0, 
            "failed": 0
        }, 
        "hits": {
            "total": 1, 
            "max_score": 0.2876821, 
            "hits": [
                {
                    "_index": "ems", 
                    "_type": "emp", 
                    "_id": "AXmw8VHfJwC9j-D14eQ_", 
                    "_score": 0.2876821, 
                    "_source": {
                        "name": "梅超风", 
                        "age": 43, 
                        "bir": "2012-12-12", 
                        "content": "Redis是一个开源的使用ANSI C语言编写、支持网络、可基于内存亦可持久化的日志型、Key-Value数据库，并提供多种语言的API", 
                        "address": "杭州"
                    }
                }
            ]
        }
    }
### ranage filter
    GET /ems/emp/_search
    {
      "query": {
        "bool": {
          "must": [
            {"term": {
              "name": {
                "value": "中国"
              }
            }}
          ],
          "filter": {
            "range": {
              "age": {
                "gte": 7,
                "lte": 20
              }
            }
          }
        }
      }
    }
    --------------------------------
    返回结果：
    {
        "took": 1, 
        "timed_out": false, 
        "_shards": {
            "total": 5, 
            "successful": 5, 
            "skipped": 0, 
            "failed": 0
        }, 
        "hits": {
            "total": 0, 
            "max_score": null, 
            "hits": [ ]
        }
    }
### exists filter
    过滤存在指定字段,获取字段不为空的索引记录使用
    GET /ems/emp/_search
    {
      "query": {
        "bool": {
          "must": [
            {"term": {
              "name": {
                "value": "中国"
              }
            }}
          ],
          "filter": {
            "exists": {
              "field":"aaa"
            }
          }
        }
      }
    }
    --------------------------------
    返回结果：
    {
        "took": 1, 
        "timed_out": false, 
        "_shards": {
            "total": 5, 
            "successful": 5, 
            "skipped": 0, 
            "failed": 0
        }, 
        "hits": {
            "total": 0, 
            "max_score": null, 
            "hits": [ ]
        }
    }
### ids filter
    过滤含有指定字段的索引记录
    GET /ems/emp/_search
    {
      "query": {
        "bool": {
          "must": [
            {"term": {
              "name": {
                "value": "中国"
              }
            }}
          ],
          "filter": {
            "ids": {
              "values": ["1","2","3"]
            }
          }
        }
      }
    }
    --------------------------------
    返回结果：
    {
        "took": 1, 
        "timed_out": false, 
        "_shards": {
            "total": 5, 
            "successful": 5, 
            "skipped": 0, 
            "failed": 0
        }, 
        "hits": {
            "total": 0, 
            "max_score": null, 
            "hits": [ ]
        }
    }

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