1、ES6.X 新類型Join 產生背景

• Mysql中多表關聯，我們可以通過left join 或者Join等實現；

• ES5.X版本，借助父子文檔實現多表關聯，類似數據庫中Join的功能；實現的核心是借助于ES5.X支持1個索引(index)下多個類型(type)。

• ES6.X版本，由于每個索引下面只支持單一的類型（type）。

• 所以，ES6.X版本如何實現Join成為大家關注的問題。

幸好，ES6.X新推出了Join類型，主要解決類似Mysql中多表關聯的問題。

2、ES6.X Join類型介紹

仍然是一個索引下，借助父子關系，實現類似Mysql中多表關聯的操作。

3、ES6.X Join類型實戰

3.1 ES6.X Join類型 Mapping定義

Join類型的Mapping如下:

核心?
- 1） “my_join_field”為join的名稱。

• 2）”question”: “answer” 指：qustion為answer的父類。

PUT my_join_index {"mappings": {"_doc": {"properties": {"my_join_field": { "type": "join","relations": {"question": "answer" }}}}} }

3.2 ES6.X join類型定義父文檔

直接上以下簡化的形式，更好理解些。

如下，定義了兩篇父文檔。?
文檔類型為父類型:”question”。

PUT my_join_index/_doc/1?refresh {"text": "This is a question","my_join_field": "question" }PUT my_join_index/_doc/2?refresh {"text": "This is another question","my_join_field": "question" }

3.3 ES6.X join類型定義子文檔

• 路由值是強制性的，因為父文件和子文件必須在相同的分片上建立索引。
• “answer”是此子文檔的加入名稱。
• 指定此子文檔的父文檔ID：1。

PUT my_join_index/_doc/3?routing=1&refresh {"text": "This is an answer","my_join_field": {"name": "answer", "parent": "1" } }PUT my_join_index/_doc/4?routing=1&refresh {"text": "This is another answer","my_join_field": {"name": "answer","parent": "1"} }

4、ES6.X Join類型約束

每個索引只允許一個Join類型Mapping定義；

父文檔和子文檔必須在同一個分片上編入索引；這意味著，當進行刪除、更新、查找子文檔時候需要提供相同的路由值。

一個文檔可以有多個子文檔，但只能有一個父文檔。

可以為已經存在的Join類型添加新的關系。

當一個文檔已經成為父文檔后，可以為該文檔添加子文檔。

5、ES6.X Join類型檢索與聚合

5.1 ES6.X Join全量檢索

GET my_join_index/_search {"query": {"match_all": {}},"sort": ["_id"] }

返回結果如下：

{"took": 1,"timed_out": false,"_shards": {"total": 5,"successful": 5,"skipped": 0,"failed": 0},"hits": {"total": 4,"max_score": null,"hits": [{"_index": "my_join_index","_type": "_doc","_id": "1","_score": null,"_source": {"text": "This is a question","my_join_field": "question"},"sort": ["1"]},{"_index": "my_join_index","_type": "_doc","_id": "2","_score": null,"_source": {"text": "This is another question","my_join_field": "question"},"sort": ["2"]},{"_index": "my_join_index","_type": "_doc","_id": "3","_score": null,"_routing": "1","_source": {"text": "This is an answer","my_join_field": {"name": "answer","parent": "1"}},"sort": ["3"]},{"_index": "my_join_index","_type": "_doc","_id": "4","_score": null,"_routing": "1","_source": {"text": "This is another answer","my_join_field": {"name": "answer","parent": "1"}},"sort": ["4"]}]} }

5.2 ES6.X 基于父文檔查找子文檔

GET my_join_index/_search {"query": {"has_parent" : {"parent_type" : "question","query" : {"match" : {"text" : "This is"}}}} }

返回結果：

{"took": 0,"timed_out": false,"_shards": {"total": 5,"successful": 5,"skipped": 0,"failed": 0},"hits": {"total": 2,"max_score": 1,"hits": [{"_index": "my_join_index","_type": "_doc","_id": "3","_score": 1,"_routing": "1","_source": {"text": "This is an answer","my_join_field": {"name": "answer","parent": "1"}}},{"_index": "my_join_index","_type": "_doc","_id": "4","_score": 1,"_routing": "1","_source": {"text": "This is another answer","my_join_field": {"name": "answer","parent": "1"}}}]} }

5.3 ES6.X 基于子文檔查找父文檔

GET my_join_index/_search { "query": {"has_child" : {"type" : "answer","query" : {"match" : {"text" : "This is question"}}}} }

返回結果：

{"took": 0,"timed_out": false,"_shards": {"total": 5,"successful": 5,"skipped": 0,"failed": 0},"hits": {"total": 1,"max_score": 1,"hits": [{"_index": "my_join_index","_type": "_doc","_id": "1","_score": 1,"_source": {"text": "This is a question","my_join_field": "question"}}]} }

5.4 ES6.X Join聚合操作實戰

以下操作含義如下：

• 1）parent_id是特定的檢索方式，用于檢索屬于特定父文檔id=1的，子文檔類型為answer的文檔的個數。
• 2）基于父文檔類型question進行聚合；
• 3）基于指定的field處理。

GET my_join_index/_search {"query": {"parent_id": { "type": "answer","id": "1"}},"aggs": {"parents": {"terms": {"field": "my_join_field#question", "size": 10}}},"script_fields": {"parent": {"script": {"source": "doc['my_join_field#question']" }}} }

返回結果：

{"took": 1,"timed_out": false,"_shards": {"total": 5,"successful": 5,"skipped": 0,"failed": 0},"hits": {"total": 2,"max_score": 0.13353139,"hits": [{"_index": "my_join_index","_type": "_doc","_id": "3","_score": 0.13353139,"_routing": "1","fields": {"parent": ["1"]}},{"_index": "my_join_index","_type": "_doc","_id": "4","_score": 0.13353139,"_routing": "1","fields": {"parent": ["1"]}}]},"aggregations": {"parents": {"doc_count_error_upper_bound": 0,"sum_other_doc_count": 0,"buckets": [{"key": "1","doc_count": 2}]}} }

6、ES6.X Join 一對多實戰

6.1 一對多定義

如下，一個父文檔question與多個子文檔answer，comment的映射定義。

PUT join_ext_index {"mappings": {"_doc": {"properties": {"my_join_field": {"type": "join","relations": {"question": ["answer", "comment"] }}}}} }

6.2 一對多對多定義

實現如下圖的祖孫三代關聯關系的定義。

question/ \/ \ comment answer||vote PUT join_multi_index {"mappings": {"_doc": {"properties": {"my_join_field": {"type": "join","relations": {"question": ["answer", "comment"], "answer": "vote" }}}}} }

孫子文檔導入數據，如下所示：

PUT join_multi_index/_doc/3?routing=1&refresh {"text": "This is a vote","my_join_field": {"name": "vote","parent": "2" } }

注意：

- 孫子文檔所在分片必須與其父母和祖父母相同 - 孫子文檔的父代號（必須指向其父親answer文檔）

7、小結

雖然ES官方文檔已經很詳細了，詳見：?
http://t.cn/RnBBLgp

總結

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