### 歡迎訪問我的GitHub
> 這裡分類和彙總了欣宸的全部原創(含配套原始碼)：[https://github.com/zq2599/blog_demos](https://github.com/zq2599/blog_demos)

- 本文是《elasticsearch實戰三部曲》的終篇，作為elasticsearch的核心功能，搜尋的重要性不言而喻，今天的實戰都會圍繞搜尋展開；

### 環境資訊
- 本次實戰用到的elasticsearch版本是6.5.4，安裝在Ubuntu 16.04.5 LTS，客戶端工具是postman6.6.1；
- 如果您需要搭建elasticsearch環境，請參考[《Linux環境快速搭建elasticsearch6.5.4叢集和Head外掛》](https://blog.51cto.com/u_13674465/5520353)；

### 基本情況介紹
- 本次實戰的elasticsearch環境以及搭建完畢，是由兩個機器搭建的叢集，並且elasticsearch-head也搭建完成：
- 一號機器，IP地址：192.168.119.152；
- 二號機器：IP地址：192.168.119.153；
- elasticsearch-head安裝在一號機器，訪問地址：http://192.168.119.152:9100
- 已經建立了索引**englishbooks**，對應的資料如下所示，請用批次命令匯入到elasticsearch：

```json
{"index":{ "_index": "englishbooks", "_type": "IT", "_id": "1" }}
{"id":"1","title":"Deep Learning","language":"python","author":"Yoshua Bengio","price":549.00,"publish_time":"2016-11-18","description":"written by three experts in the field, deep learning is the only comprehensive book on the subject."}
{"index":{ "_index": "englishbooks", "_type": "IT", "_id": "2" }}
{"id":"2","title":"Compilers","language":"c","author":"Alfred V.Aho","price":62.50,"publish_time":"2011-01-01","description":"In the time since the 1986 edition of this book, the world of compiler designhas changed significantly."}
{"index":{ "_index": "englishbooks", "_type": "IT", "_id": "3" }}
{"id":"3","title":"Core Java","language":"java","author":"Horstmann","price":85.90,"publish_time":"2016-06-01","description":"The book is aimed at experienced programmers who want to learn how to write useful Java applications and applets. "}
{"index":{ "_index": "englishbooks", "_type": "IT", "_id": "4" }}
{"id":"4","title":"Thinking in Java","language":"java","author":"Bruce Eckel","price":70.10,"publish_time":"2015-07-06","description":"Thinking in Java should be read cover to cover by every Java programmer, then kept close at hand for frequent reference. The exercises are challenging, and the chapter on Collections is superb!"}
{"index":{ "_index": "englishbooks", "_type": "IT", "_id": "5" }}
{"id":"5","title":"The Go Programming Language","language":"go","author":"Alan A.A.Donovan","price":63.90,"publish_time":"2016-01-01","description":"A declaration's lexical block determines its scope， which may be large or small. The declarations of built—in types， functions， and constants like int， len， and true are in the universe block and can be referred to throughout the entire program."}

```

- 相關的文件是批次匯入的，關於文件資料和批次操作的細節請參考[《elasticsearch實戰三部曲之二：文件操作》](https://blog.51cto.com/u_13674465/5527797)；

- books索引的文件內容在head中展示如下圖：
![在這裡插入圖片描述](https://img-blog.csdnimg.cn/20190113161306932.jpg?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JvbGluZ19jYXZhbHJ5,size_16,color_FFFFFF,t_70)

### 資料格式說明
- 為了便於和讀者溝通，我們來約定一下如何在文章中表達請求和響應的資訊：

- 假設透過Postman工具向伺服器傳送一個PUT型別的請求，地址是：http://192.168.119.152:9200/test001/article/1
- 請求的內容是JSON格式的，內容如下：

```shell
{
	“id”:1,
	"title":"標題a",
	"posttime":"2019-01-12",
	"content":"一起來熟悉文件相關的操作"
}
```

- 對於上面的請求，我在文章中就以如下格式描述：
```shell
PUT test001/article/1

{
	“id”:1,
	"title":"標題a",
	"posttime":"2019-01-12",
	"content":"一起來熟悉文件相關的操作"
}
```
- 讀者您看到上述內容，就可以在postman中發起PUT請求，地址是"test001/article/1"前面加上您的伺服器地址，內容是上面的JSON；

### 本文中的文件內容暫不涉及中文
- 文中資料都是英文的，避免在因分詞器的分詞問題導致搜尋不到對應的中文結果，分詞器相關的知識會在另一篇文章中詳細介紹；

### 檢視所有資料
```shell
GET englishbooks/_search

{
	"query":{
		"match_all":{}
	}
}
```
- 上述查詢返回索引books的所有記錄，並且文件得分收是1；
- 您可以將請求的整個JSON刪除，只用books/_search這個URL來試試，也能得到所有資料，這是match_all的簡寫；

### 數字欄位的精確匹配
- 查詢價格等於549的記錄：

```shell
GET englishbooks/_search

{
	"query":{
		"constant_score":{
			"filter":{
				"term":{"price":549}
			}
		}
	}
}
```

- 得到結果：

```json
{
    "took": 4,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 1,
        "max_score": 1,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "1",
                "_score": 1,
                "_source": {
                    "id": "1",
                    "title": "Deep Learning",
                    "language": "python",
                    "author": "Yoshua Bengio",
                    "price": 549,
                    "publish_time": "2016-11-18",
                    "description": "written by three experts in the field, deep learning is the only comprehensive book on the subject."
                }
            }
        ]
    }
}
```
- 請求引數中使用了constant_score 後，查詢將以非評分模式來執行 term，並以一作為統一評分；

### 檢視分詞效果
- text型別的欄位會被分詞後構建倒排索引，來看看title欄位的值為"Core Java"時的分詞效果：

```shell
GET englishbooks/_analyze

{
	"field":"title",
	"text":"Core Java"
}
```

- 響應如下所示，"Core Java"被分"core"和"java"兩個詞，也就是說我們以詞項"core"或"java"搜尋title欄位都能收到對應文件：

```json
{
    "tokens": [
        {
            "token": "core",
            "start_offset": 0,
            "end_offset": 4,
            "type": "<alphanum>",
            "position": 0
        },
        {
            "token": "java",
            "start_offset": 5,
            "end_offset": 9,
            "type": "<alphanum>",
            "position": 1
        }
    ]
}
```
- 需要注意的是分詞後的結果都是小寫，這是分詞器的處理結果；

### 詞項查詢（term query）

- 前面我們檢視分詞效果發現"Core Java"被分"core"和"java"兩個詞，現在就以"java"為關鍵詞搜尋一下試試：

```shell
GET englishbooks/_search

{
	"query":{
		"term":{"title":"java"}
	}
}
```

- 結果如下，title中有java關鍵詞的兩個文件都被搜到：

```json
{
    "took": 4,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 2,
        "max_score": 0.5754429,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "4",
                "_score": 0.5754429,
                "_source": {
                    "id": "4",
                    "title": "Thinking in Java",
                    "language": "java",
                    "author": "Bruce Eckel",
                    "price": 70.1,
                    "publish_time": "2015-07-06",
                    "description": "Thinking in Java should be read cover to cover by every Java programmer, then kept close at hand for frequent reference. The exercises are challenging, and the chapter on Collections is superb!"
                }
            },
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "3",
                "_score": 0.2876821,
                "_source": {
                    "id": "3",
                    "title": "Core Java",
                    "language": "java",
                    "author": "Horstmann",
                    "price": 85.9,
                    "publish_time": "2016-06-01",
                    "description": "The book is aimed at experienced programmers who want to learn how to write useful Java applications and applets. "
                }
            }
        ]
    }
}
```

### 分詞查詢（match query）
- term query的特點是將輸入的內容作為一個詞項來用，例如以下的查詢是沒有結果的：

```shell
GET englishbooks/_search

{
	"query":{
		"term":{"title":"core java"}
	}
}
```

- 上述查詢沒有結果的原因，是因為"core java"被當做一個詞項去查詢了，而title的分詞結果中只有"core"、"java"這些分詞過的詞項，並沒有一個叫做"core java"的詞項，所以搜不到結果；

- 如果輸入的查詢條件"core java"也被做一次分詞處理，再把處理結果"core"和"java"用來搜尋，應該就能得到結果了，match query就是用來對輸入條件做分詞處理的，如下：

```shell
GET englishbooks/_search

{
	"query":{
		"match":{"title":"Core Java"}
	}
}
```

- 搜尋結果如下，包含了java的兩條記錄都被查出來了：

```json
{
    "took": 8,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 2,
        "max_score": 0.5754429,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "4",
                "_score": 0.5754429,
                "_source": {
                    "id": "4",
                    "title": "Thinking in Java",
                    "language": "java",
                    "author": "Bruce Eckel",
                    "price": 70.1,
                    "publish_time": "2015-07-06",
                    "description": "Thinking in Java should be read cover to cover by every Java programmer, then kept close at hand for frequent reference. The exercises are challenging, and the chapter on Collections is superb!"
                }
            },
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "3",
                "_score": 0.5753642,
                "_source": {
                    "id": "3",
                    "title": "Core Java",
                    "language": "java",
                    "author": "Horstmann",
                    "price": 85.9,
                    "publish_time": "2016-06-01",
                    "description": "The book is aimed at experienced programmers who want to learn how to write useful Java applications and applets. "
                }
            }
        ]
    }
}
```

- 如果我們的本意是隻要"Core Java"的匹配結果，上面的結果顯然是不符合要求的，此時可以給查詢條件加個**"operator":"and"**屬性，就會查詢匹配了所有關鍵詞的文件，注意json的結構略有變化，以前title的屬性是搜尋條件，現在變成了一個json物件，裡面的query屬性是原來的搜尋條件：

```shell
GET englishbooks/_search

{
	"query":{
		"match":{
			"title":{
				"query":"Core Java",
				"operator":"and"
			}
		}
	}
}
```

- 這次的搜尋結果就是同時匹配了"core"和"java"兩個詞項的記錄了(為什麼core和java是小寫？ 因為"Core Java"被分詞後改為了小寫，再去搜尋的)：

```json
{
    "took": 11,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 1,
        "max_score": 0.5753642,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "3",
                "_score": 0.5753642,
                "_source": {
                    "id": "3",
                    "title": "Core Java",
                    "language": "java",
                    "author": "Horstmann",
                    "price": 85.9,
                    "publish_time": "2016-06-01",
                    "description": "The book is aimed at experienced programmers who want to learn how to write useful Java applications and applets. "
                }
            }
        ]
    }
}
```

###  match_phrase搜尋
- match_phrase搜尋和前面的match搜尋相似，並且有以下兩個特點：
- 分詞後的所有詞項都要匹配上，也就是前面的**"operator":"and"**屬性的效果；
- 分析後的詞項順序要和搜尋欄位的順序一致，才能匹配上；

```shell
GET englishbooks/_search

{
	"query":{
		"match_phrase":{"title":"Core Java"}
	}
}
```

- 上述查詢可以搜尋到結果，但如果將"Core Java"改成"Java Core"就搜不到結果了，但是match query用"Java Core"是可以搜到結果的；

### match_phrase_prefix搜尋

- match_phrase_prefix的功能和前面的match_phrase類似，不過match_phrase_prefix支援最後一個詞項做字首匹配，如下所示，"Core J"這個搜尋條件用match_phrase是搜不到結果的，但是match_phrase_prefix可以，因為"J"可以作為字首和"Java"匹配：

```shell
GET englishbooks/_search

{
	"query":{
		"match_phrase":{"title":"Core J"}
	}
}
```

### multi_match搜素
- multi_match是在match的基礎上支援多欄位搜尋，以下查詢就是用"1986"和"deep"這兩個詞項，同時搜尋title和description兩個欄位：

```shell
GET englishbooks/_search

{
	"query":{
		"multi_match":{
			"query":"1986 deep",
			"fields":["title", "description"]
		}
	}
}
```

- 響應如下，可見title和description中含有詞項"1986"或者"deep"的文件都被返回了：
```json
{
    "took": 4,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 2,
        "max_score": 0.79237825,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "2",
                "_score": 0.79237825,
                "_source": {
                    "id": "2",
                    "title": "Compilers",
                    "language": "c",
                    "author": "Alfred V.Aho",
                    "price": 62.5,
                    "publish_time": "2011-01-01",
                    "description": "In the time since the 1986 edition of this book, the world of compiler designhas changed significantly."
                }
            },
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "1",
                "_score": 0.2876821,
                "_source": {
                    "id": "1",
                    "title": "Deep Learning",
                    "language": "python",
                    "author": "Yoshua Bengio",
                    "price": 549,
                    "publish_time": "2016-11-18",
                    "description": "written by three experts in the field, deep learning is the only comprehensive book on the subject."
                }
            }
        ]
    }
}
```

### terms query
- terms是term查詢的升級，用來查詢多個詞項：

```shell
GET englishbooks/_search

{
	"query":{
		"terms":{
			"title":["deep", "core"]
		}
	}
}
```

- 響應如下，title中含有deep和core的文件都被查到：

```json
{
    "took": 5,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 2,
        "max_score": 1,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "1",
                "_score": 1,
                "_source": {
                    "id": "1",
                    "title": "Deep Learning",
                    "language": "python",
                    "author": "Yoshua Bengio",
                    "price": 549,
                    "publish_time": "2016-11-18",
                    "description": "written by three experts in the field, deep learning is the only comprehensive book on the subject."
                }
            },
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "3",
                "_score": 1,
                "_source": {
                    "id": "3",
                    "title": "Core Java",
                    "language": "java",
                    "author": "Horstmann",
                    "price": 85.9,
                    "publish_time": "2016-06-01",
                    "description": "The book is aimed at experienced programmers who want to learn how to write useful Java applications and applets. "
                }
            }
        ]
    }
}
```

### 範圍查詢
- range query是範圍查詢，例如查詢publish_time在"2016-01-01"到"2016-12-31"之間的文件：

```shell
GET englishbooks/_search

{
	"query":{
		"range":{
			"publish_time":{
				"gte":"2016-01-01",
				"lte":"2016-12-31",
				"format":"yyyy-MM-dd"
			}
		}
	}
}
```

- 篇幅所限，此處略去返回結果；

###  exists query
- exists query返回的是欄位中至少有一個非空值的文件：

```shell
GET englishbooks/_search

{
	"query":{
		"exists":{
			"field":"author"
		}
	}
}
```

###  字首查詢
- 用於查詢某個欄位是否以給定字首開始：

```shell
GET englishbooks/_search

{
	"query":{
		"prefix":{
			"title":"cor"
		}
	}
}
```

- 以上請求可以查到title欄位為"Core Java"的文件：

```json
{
    "took": 6,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 1,
        "max_score": 1,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "3",
                "_score": 1,
                "_source": {
                    "id": "3",
                    "title": "Core Java",
                    "language": "java",
                    "author": "Horstmann",
                    "price": 85.9,
                    "publish_time": "2016-06-01",
                    "description": "The book is aimed at experienced programmers who want to learn how to write useful Java applications and applets. "
                }
            }
        ]
    }
}
```

### 萬用字元查詢

- 以下查詢，可以搜到title欄位中含有"core"的文件，另外需要注意的是，"?"匹配一個字元，"*"匹配零個或者多個字元：

```shell
GET englishbooks/_search

{
	"query":{
		"wildcard":{
			"title":"cor?"
		}
	}
}
```

### 正規表示式

- 使用屬性**regexp**可以進行正規表示式查詢，例如查詢description欄位帶有4位數字的分詞的文件：

```shell
GET englishbooks/_search

{
	"query":{
		"regexp":{
			"description":"[0-9]{4}"
		}
	}
}
```

- 查詢結果如下，description欄位中帶有數字**1986**：

```json
{
    "took": 4,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 1,
        "max_score": 1,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "2",
                "_score": 1,
                "_source": {
                    "id": "2",
                    "title": "Compilers",
                    "language": "c",
                    "author": "Alfred V.Aho",
                    "price": 62.5,
                    "publish_time": "2011-01-01",
                    "description": "In the time since the 1986 edition of this book, the world of compiler designhas changed significantly."
                }
            }
        ]
    }
}
```

### 模糊查詢(fuzzy query)
- fuzzy是透過計算詞項與文件的編輯距離來得到結果的，例如查詢description欄位還有分詞"1986"的時候，不小心輸入了"1987"，透過fuzzy查詢也能得到結果，只是得分變低了，請求內容如下所示：

```shell
GET englishbooks/_search

{
	"query":{
		"fuzzy":{
			"description":"1987"
		}
	}
}
```

- 搜尋到的文件如下所示，得分只有0.5942837，低於用"1986"查詢的0.79237825：

```json
{
    "took": 5,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 1,
        "max_score": 0.5942837,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "2",
                "_score": 0.5942837,
                "_source": {
                    "id": "2",
                    "title": "Compilers",
                    "language": "c",
                    "author": "Alfred V.Aho",
                    "price": 62.5,
                    "publish_time": "2011-01-01",
                    "description": "In the time since the 1986 edition of this book, the world of compiler designhas changed significantly."
                }
            }
        ]
    }
}
```

- 需要注意的是，fuzzy查詢時消耗資源較大；

### 複合查詢
- 常用到的複合查詢是bool query，可以用下表中的條件組合查詢：

- 以下條件，搜尋的是title中帶有java，但是不包含core的文件：

```shell
GET englishbooks/_search

{
	"query":{
		"bool":{
			"must":{
				"term":{"title":"java"}	
			},
			"must_not":[
			{"term":{"title":"core"}}
			]
		}
	}
}
```

- 得到的文件中，帶有core詞項的已經被過濾了：

```json
{
    "took": 3,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 1,
        "max_score": 0.5754429,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "4",
                "_score": 0.5754429,
                "_source": {
                    "id": "4",
                    "title": "Thinking in Java",
                    "language": "java",
                    "author": "Bruce Eckel",
                    "price": 70.1,
                    "publish_time": "2015-07-06",
                    "description": "Thinking in Java should be read cover to cover by every Java programmer, then kept close at hand for frequent reference. The exercises are challenging, and the chapter on Collections is superb!"
                }
            }
        ]
    }
}
```

### 指令碼查詢
- 可用指令碼進行查詢，如下是查詢價格大於100的所有文件：

```shell
GET englishbooks/_search

{
	"query":{
		"bool":{
			"must":{
				"script":{
					"script":{
						"inline":"doc['price'].value>500",
						"lang":"painless"
					}
				}	
			}
		}
	}
}
```

- 得到的結果只有price大於500的文件：

```json
{
    "took": 8,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 1,
        "max_score": 1,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "1",
                "_score": 1,
                "_source": {
                    "id": "1",
                    "title": "Deep Learning",
                    "language": "python",
                    "author": "Yoshua Bengio",
                    "price": 549,
                    "publish_time": "2016-11-18",
                    "description": "written by three experts in the field, deep learning is the only comprehensive book on the subject."
                }
            }
        ]
    }
}
```

### 指定排序欄位
- 預設的排序方式是按照評分來排序的（也就是相關度排序），可以用sort屬性來設定排序欄位，下面的請求指定了按照price欄位降序排序：

```shell
{
	"query":{
		"term":{"title":"java"}
	},
	"sort":[
		{"price":{"order":"desc"}}
	]
}
```

- 得到結果：

```json
{
    "took": 4,
    "timed_out": false,
    "_shards": {
        "total": 5,
        "successful": 5,
        "skipped": 0,
        "failed": 0
    },
    "hits": {
        "total": 2,
        "max_score": null,
        "hits": [
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "3",
                "_score": null,
                "_source": {
                    "id": "3",
                    "title": "Core Java",
                    "language": "java",
                    "author": "Horstmann",
                    "price": 85.9,
                    "publish_time": "2016-06-01",
                    "description": "The book is aimed at experienced programmers who want to learn how to write useful Java applications and applets. "
                },
                "sort": [
                    85.9
                ]
            },
            {
                "_index": "englishbooks",
                "_type": "IT",
                "_id": "4",
                "_score": null,
                "_source": {
                    "id": "4",
                    "title": "Thinking in Java",
                    "language": "java",
                    "author": "Bruce Eckel",
                    "price": 70.1,
                    "publish_time": "2015-07-06",
                    "description": "Thinking in Java should be read cover to cover by every Java programmer, then kept close at hand for frequent reference. The exercises are challenging, and the chapter on Collections is superb!"
                },
                "sort": [
                    70.1
                ]
            }
        ]
    }
}
```

- 以上就是常用的搜尋操作了，至此，《elasticsearch實戰三部曲》系列就全部完成，三篇文章列舉的是一些常用的基本操作，希望能幫助讀者您快速熟悉elasticsearch，後面我們們再一起深入實戰；

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elasticsearch實戰三部曲之三：搜尋操作

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