nest 類型是對(duì)象數(shù)據(jù)類型的一種特殊版本，允許以一種可以獨(dú)立查詢對(duì)象數(shù)組元素的方式對(duì)對(duì)象數(shù)組進(jìn)行索引。
Thenestedtype is a specialised version of theobjectdata type that allows arrays of objects to be indexed in a way that they can be queried independently of each other.
nest類型的官方文檔介紹
nested類型的限制：
// todo — 待更新
e.g.
重慶分公司
重慶分公司
PUT my-index-000001/_doc/1
{
"user": [
{
"first": "John",
"last": "Smith"
},
{
"first": "Alice",
"last": "White"
}
]
}上述的插入文檔的操作在內(nèi)部會(huì)將其轉(zhuǎn)換成如下：
{
"user.first": ["john", "alice"],
"user.last": ["smith", "white"]
}可以看出 user.first、user.last 字段都會(huì)平鋪成多值的字段，alice、white 之間還有 john、smith 之間的關(guān)聯(lián)關(guān)系會(huì)丟失。
導(dǎo)致下面的查詢的結(jié)果也是不準(zhǔn)確的：
GET my-index-000001/_search
{
"query": {
"bool": {
"must": [
{
"match": {
"user.first": "Alice"
}
},
{
"match": {
"user.last": "Smith"
}
}
]
}
}
}對(duì)此，可以采用 nested 類型解決這種問(wèn)題。
PUT my-index-000001
{
"mappings": {
"properties": {
"user": {
"type": "nested",
"properties": {
"first": {
"type": "text"
},
"last": {
"type": "text"
}
}
}
}
}
}PUT my-index-000001/_doc/1
{
"user": [
{
"first": "John",
"last": "Smith"
},
{
"first": "Alice",
"last": "White"
}
]
}GET my-index-000001/_search
{
"query": {
"nested": {
"path": "user",
"query": {
"bool": {
"must": [
{
"match": {
"user.first": "Alice"
}
},
{
"match": {
"user.last": "White"
}
}
]
}
}
}
}
}即嵌套查詢。針對(duì) nested 類型字段的查詢。
自己的理解：前面說(shuō)到 nested 類型是允許以一種可以獨(dú)立查詢對(duì)象數(shù)組元素的方式對(duì)對(duì)象數(shù)組進(jìn)行索引，也就是說(shuō)對(duì)象數(shù)組元素即子對(duì)象作為一個(gè)整體進(jìn)行匹配，如果匹配成功，則返回父文檔。
nested query 的官方文檔介紹
path：（必須）想要查詢的嵌套對(duì)象
query：（必須）基于嵌套對(duì)象，想要查詢的內(nèi)容
score_mode：匹配的子對(duì)象集合的分?jǐn)?shù)如何影響父文檔的關(guān)聯(lián)性分?jǐn)?shù)
ignore_unmapped：當(dāng) path 沒(méi)有匹配到時(shí)，如果設(shè)置為 true，則返回空文檔；如果設(shè)置為 false，則報(bào)錯(cuò)。默認(rèn) false
多層嵌套
PUT drivers
{
"mappings": {
"properties": {
"driver": {
"type": "nested",
"properties": {
"last_name": {
"type": "text"
},
"vehicle": {
"type": "nested",
"properties": {
"make": {
"type": "text"
},
"model": {
"type": "text"
}
}
}
}
}
}
}
}PUT /drivers/_doc/1
{
"driver": {
"last_name": "McQueen",
"vehicle": [
{
"make": "Powell Motors",
"model": "Canyonero"
},
{
"make": "Miller-Meteor",
"model": "Ecto-1"
}
]
}
}PUT /drivers/_doc/2?refresh
{
"driver": {
"last_name": "Hudson",
"vehicle": [
{
"make": "Mifune",
"model": "Mach Five"
},
{
"make": "Miller-Meteor",
"model": "Ecto-1"
}
]
}
}GET drivers/_search
{
"query": {
"nested": {
"path": "driver",
"query": {
"nested": {
"path": "driver.vehicle",
"query": {
"bool": {
"must": [
{
"match": {
"driver.vehicle.make": "Powell Motors"
}
},
{
"match": {
"driver.vehicle.model": "Canyonero"
}
}
]
}
}
}
}
}
}
}join 類型是一種特殊類型，可以在相同索引下的多個(gè)文檔中創(chuàng)建父子關(guān)系。它會(huì)在 relations 字段中定義一組可能的關(guān)系，包括父名稱和子名稱。
Thejoindata type is a special field that creates parent/child relation within documents of the same index. Therelationssection defines a set of possible relations within the documents, each relation being a parent name and a child name.
e.g.
PUT my-index-000001
{
"mappings": {
"properties": {
"my_join_field": {
"type": "join",
"relations": {
"question": "answer"
}
},
"text": {
"type": "text"
}
}
}
}PUT my-index-000001/_doc/1
{
"my_join_field": {
"name": "question"
},
"text": "This is a question"
}對(duì)于父文檔來(lái)說(shuō)，上述的文檔可以簡(jiǎn)寫(xiě)成如下這種形式：
PUT my-index-000001/_doc/1
{
"my_join_field": "question",
"text": "This is a question"
}但是對(duì)于子文檔來(lái)說(shuō)，name、parent 一定要有。
PUT my-index-000001/_doc/3?routing=1
{
"my_join_field": {
"name": "answer",
"parent": "1"
},
"text": "This is an answer"
}創(chuàng)建子文檔，必須指定routing參數(shù)值
join 類型的限制
join 類型的字段使用全局序號(hào)來(lái)提高連接查詢的速度。在分片發(fā)生變化后，需要重建全局序號(hào)。存儲(chǔ)在一個(gè)分片中的 parent id 值越多，重建 join 類型的字段的全局序號(hào)所需的時(shí)間越長(zhǎng)。默認(rèn)情況下，全局序號(hào)會(huì)預(yù)先構(gòu)建，如果索引發(fā)生了變化，join 類型的字段的全局序號(hào)就會(huì)作為刷新的一部分進(jìn)行重新構(gòu)建。
如果 join 類型的字段不經(jīng)常使用并且寫(xiě)操作頻繁時(shí)，可以選擇禁用預(yù)先加載全局序號(hào)，如下：
PUT my-index-000001
{
"mappings": {
"properties": {
"my_join_field": {
"type": "join",
"relations": {
"question": "answer"
},
"eager_global_ordinals": false
}
}
}
}此外，可以一個(gè)父關(guān)系對(duì)應(yīng)多個(gè)子關(guān)系：
PUT my-index-000001
{
"mappings": {
"properties": {
"my_join_field": {
"type": "join",
"relations": {
"question": ["answer", "comment"]
}
}
}
}
}還可以定義多層的關(guān)系模型：
PUT my-index-000001
{
"mappings": {
"properties": {
"my_join_field": {
"type": "join",
"relations": {
"question": ["answer", "comment"],
"answer": "vote"
}
}
}
}
}不推薦使用上述的多層的關(guān)系模型。每一層級(jí)關(guān)系在查詢時(shí)都會(huì)增加內(nèi)存和計(jì)算的開(kāi)銷。
Has_Child Query返回與提供的查詢相匹配的子文檔關(guān)聯(lián)的父文檔?？梢允褂?join 類型的字段在不同文檔中建立父子關(guān)系。
Returns parent documents whose joined child documents match a provided query. You can create parent-child relationships between documents in the same index using a join field mapping.
因?yàn)?has_child 查詢執(zhí)行關(guān)聯(lián)查詢，所以它比其它查詢要慢。并且它會(huì)隨著匹配的子文檔數(shù)量增加而性能降低。搜索中的每個(gè) has_child 查詢會(huì)顯著增加查詢時(shí)間。
Because it performs a join, the has_child is slow compared to other queries. Its performance degrades as the number of matching child documents pointing to unique parent documents increases. Eachhas_childquery in a search can increase query time significantly.
has_child query 的官方文檔介紹
type：（必須）join 類型的字段中定義的子關(guān)系名稱
query：（必須）基于 type 查詢對(duì)應(yīng)的子文檔，如果有子文檔匹配查詢，則返回與之關(guān)聯(lián)的父文檔
ignore_unmapped：如果 type 沒(méi)有匹配到，選擇返回空內(nèi)容還是返回一個(gè)錯(cuò)誤。默認(rèn) false
max_children：要求父文檔中子文檔的數(shù)量<=該值時(shí)，父文檔才能從結(jié)果中返回
min_children：要求父文檔中子文檔的數(shù)量>=該值時(shí)，父文檔才能從結(jié)果中返回
score_mode：匹配的子文檔的分?jǐn)?shù)如何影響父文檔的關(guān)聯(lián)性分?jǐn)?shù)。默認(rèn) none
e.g.
PUT my-index-000001
{
"mappings": {
"properties": {
"my_join_field": {
"type": "join",
"relations": {
"question": "answer"
}
},
"text": {
"type": "text"
}
}
}
}PUT my-index-000001/_doc/1
{
"my_join_field": {
"name": "question"
},
"text": "This is a question"
}
PUT my-index-000001/_doc/2
{
"my_join_field": {
"name": "question"
},
"text": "This is another question"
}
PUT my-index-000001/_doc/3?routing=1
{
"my_join_field": {
"name": "answer",
"parent": "1"
},
"text": "This is an answer"
}
PUT my-index-000001/_doc/4?routing=2
{
"my_join_field": {
"name": "answer",
"parent": "2"
},
"text": "This is another answer"
}
PUT my-index-000001/_doc/5?routing=2
{
"my_join_field": {
"name": "answer",
"parent": "2"
},
"text": "This is another answer"
}創(chuàng)建子文檔，必須指定routing參數(shù)值
GET my-index-000001/_search
{
"query": {
"has_child": {
"type": "answer",
"ignore_unmapped": true,
"min_children": 2,
"query": {
"match": {
"text": "answer"
}
}
}
}
}值得注意的是，不能使用標(biāo)準(zhǔn)的 sort options 對(duì) has_child 查詢結(jié)果排序，但是可以使用 function_score 查詢，并且按照 _score 排序。
GET my-index-000001/_search
{
"query": {
"has_child": {
"type": "answer",
"score_mode": "max",
"query": {
"function_score": {
"query": {
"match": {
"text": "answer"
}
},
"script_score": {
"script": "_score"
}
}
}
}
}
}返回與提供的查詢相匹配的父文檔關(guān)聯(lián)的子文檔?？梢允褂?join 類型的字段在不同文檔中建立父子關(guān)系。
Returns child documents whose joined parent documents match a provided query. You can create parent-child relationships between documents in the same index using a join field mapping.
因?yàn)?has_parent 查詢執(zhí)行關(guān)聯(lián)查詢，所以它比其它查詢要慢。并且它會(huì)隨著匹配的父文檔的數(shù)量增加而性能降低。搜索中的每個(gè) has_parent 查詢會(huì)顯著增加查詢時(shí)間。
Because it performs a join, thehas_parentquery is slow compared to other queries. Its performance degrades as the number of matching parent documents increases. Eachhas_parentquery in a search can increase query time significantly.
has_parent query 的官方文檔介紹
parent_type：（必須）join 類型的字段中定義的父關(guān)系名稱
query：（必須）基于 parent_type 查詢對(duì)應(yīng)的父文檔，如果有父文檔匹配查詢，則返回與之關(guān)聯(lián)的子文檔
ignore_unmapped：如果 parent_type 沒(méi)有匹配到，選擇返回空內(nèi)容還是返回一個(gè)錯(cuò)誤。默認(rèn) false
score：是否將匹配到的父文檔的關(guān)聯(lián)性分?jǐn)?shù)聚合到對(duì)應(yīng)的子文檔中。默認(rèn) false
e.g.
GET my-index-000001/_search
{
"query": {
"has_parent": {
"parent_type": "question",
"score": false,
"query": {
"match": {
"text": "question"
}
}
}
}
}值得注意的是，不能使用標(biāo)準(zhǔn)的 sort options 對(duì) has_child 查詢結(jié)果排序，但是可以使用 function_score 查詢，并且按照 _score 排序。
GET my-index-000001/_search
{
"query": {
"has_parent": {
"parent_type": "question",
"score": true,
"query": {
"function_score": {
"query": {
"match": {
"text": "question"
}
},
"script_score": {
"script": "_score"
}
}
}
}
}
}返回與指定父文檔關(guān)聯(lián)的所有子文檔?？梢允褂?join 類型的字段在不同文檔中建立父子關(guān)系。
Returns child documents joined to a specific parent document. You can use a join field mapping to create parent-child relationships between documents in the same index.
parent_id query 官方文檔的介紹
type：（必須）join 類型字段定義的子關(guān)系
id：（必須）父文檔的id
ignore_unmapped：如果 type 沒(méi)有匹配到，選擇返回空內(nèi)容還是返回一個(gè)錯(cuò)誤。默認(rèn) false
true：返回空內(nèi)容
false：返回一個(gè)錯(cuò)誤
e.g.
GET my-index-000001/_search
{
"query": {
"parent_id": {
"type": "answer",
"id": 1
}
}
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