Elasticsearch 索引文檔

內容主要通過翻譯官方文檔而來，版本7.10

1. 索引文檔操作(通過curl實現)

curl -X PUT "localhost:9200/twitter/_doc/1" -H 'Content-Type: application/json' -d'

{

? ? "user" : "kimchy",

? ? "post_date" : "2009-11-15T14:12:12",

? ? "message" : "trying out Elasticsearch"

}

'

-X 選項: 指定curl的請求操作，默認是GET，也可以是PUT POST DELETE

-H 選項: 傳入請求頭

-d 選項: data，數據內容選項

不存在索引時，會自動創建。當然可以進行設置(通過action.auto_create_index)。

PUT _cluster/settings

{

? ? "persistent": {

? ? ? ? "action.auto_create_index": "twitter,index10,-index1*,+ind*"?

? ? }

}

注: 名稱為twitter,index10的索引會創建，不符合index1*格式，但符合ind*格式也會被創建。

PUT _cluster/settings

{

? ? "persistent": {

? ? ? ? "action.auto_create_index": "false"?

? ? }

}

注: 默認全部不自動創建。會提示錯誤。如例子: {"error":{"root_cause":[{"type":"index_not_found_exception","reason":"no such index [mytwitter]"

PUT _cluster/settings

{

? ? "persistent": {

? ? ? ? "action.auto_create_index": "true"?

? ? }

}

注: 默認全部自動創建

默認的MAPPING規則，一個索引下只允許有一個type.

例如試圖創建第二個名為mydoc的type:

curl -X PUT "localhost:9200/twitter/mydoc/1" -H 'Content-Type: application/json' -d'

{

? ? "user" : "kimchy",

? ? "post_date" : "2009-11-15T14:12:12",

? ? "message" : "trying out Elasticsearch"

}

'

會產生報錯:{"error":{"root_cause":[{"type":"illegal_argument_exception","reason":"Rejecting mapping update to [twitter] as the final mapping would have more?

than 1 type: [_doc, mydoc]"}],"type":"illegal_argument_exception","reason":"Rejecting mapping update to [twitter] as the final mapping would have more than 1?

type

2 索引文檔的op_type選項（只允許新建，不允許更新文檔):

如

curl -X PUT "localhost:9200/twitter/_doc/1?op_type=create" -H 'Content-Type: application/json' -d'

{

? ? "user" : "kimchy",

? ? "post_date" : "2009-11-15T14:12:12",

? ? "message" : "trying out Elasticsearch"

}

'

如果索引文檔twitter/_doc/1已經存在，創建就會失敗。

與上面等價的寫法:

curl -X PUT "localhost:9200/twitter/_create/1" -H 'Content-Type: application/json' -d'

{

? ? "user" : "kimchy",

? ? "post_date" : "2009-11-15T14:12:12",

? ? "message" : "trying out Elasticsearch"

}

'

文檔ID的自動生成:

如果沒有指定文檔ID，系統會自動生成一個唯一ID(索引該文檔理論肯定是新創建的，不會更新其他文檔):

例:

curl -X POST "localhost:9200/twitter/_doc/" -H 'Content-Type: application/json' -d'

{

? ? "user" : "mjj",

? ? "post_date" : "2009-11-15T14:12:12",

? ? "message" : "test Elasticsearch"

}

'

返回結果(部分): {"_index":"twitter","_type":"_doc","_id":"olLK42oBqV8-hMggVV3X"

3 樂觀的并發控制:

Optimistic concurrency controledit

Index operations can be made conditional and only be performed if the last modification to the document was assigned the sequence number and primary term?

specified by the if_seq_no and if_primary_term parameters. If a mismatch is detected, the operation will result in a VersionConflictException and a status?

code of 409. See Optimistic concurrency control for more details.

索引文檔結束后，返回結果中會包含一個序號:_seq_no。索引文檔前會獲取下一個序號，作為自己的序號，結束后會再獲取序號，進行比較。如果序號不一致，說明有其他程序索

引了文檔。那么該次操作就返回409號錯誤。

4. Routing(文檔存放于那個物理shard)

By default, shard placement ? or routing ? is controlled by using a hash of the document’s id value. For more explicit control, the value fed into the hash?

function used by the router can be directly specified on a per-operation basis using the routing parameter. For example:

POST twitter/_doc?routing=kimchy

{

? ? "user" : "kimchy",

? ? "post_date" : "2009-11-15T14:12:12",

? ? "message" : "trying out Elasticsearch"

}

In the example above, the "_doc" document is routed to a shard based on the routing parameter provided: "kimchy".

When setting up explicit mapping, the _routing field can be optionally used to direct the index operation to extract the routing value from the document?

itself. This does come at the (very minimal) cost of an additional document parsing pass. If the _routing mapping is defined and set to be required, the?

index operation will fail if no routing value is provided or extracted.

默認情況下，系統通過對文檔id進行hash運算，確定存放于具體的shard。但我們也可以通過指定routing參數，使hash函數對所提過的參數值進行運算，確定shard。

而且，還可以在mapping中，通過設置_routing字段來指示用文檔中的哪個值來進行hash運算。但是如果索引的文檔中沒有包含mapping設置中的字段，將會產生報錯。

5 Wait For Active Shards

默認設置下，primary shard索引完文檔就完成了操作。

但可以通過index.write.wait_for_active_shards調整，確保有多個shard已保存了變更，默認該值為1(primay shard也算1個shard)。

如果設置為2，表示primary shard完成索引后，還要復制一份變更到另一個replica shard才行，replica shard完成前就需要等待。

如果index.write.wait_for_active_shards設置成all，就是所有num of shards+1. 索引操作需要有新的節點加入才能完成。

number_of_replicas數表示所需的replican shards. 但active shards包含primary shard.

例子:

For example, suppose we have a cluster of three nodes, A, B, and C and we create an index index with the number of replicas set to 3 (resulting in 4 shard?

copies, one more copy than there are nodes). If we attempt an indexing operation, by default the operation will only ensure the primary copy of each shard is?

available before proceeding. This means that even if B and C went down, and A hosted the primary shard copies, the indexing operation would still proceed?

with only one copy of the data. If wait_for_active_shards is set on the request to 3 (and all 3 nodes are up), then the indexing operation will require 3?

active shard copies before proceeding, a requirement which should be met because there are 3 active nodes in the cluster, each one holding a copy of the?

shard. However, if we set wait_for_active_shards to all (or to 4, which is the same), the indexing operation will not proceed as we do not have all 4 copies?

of each shard active in the index. The operation will timeout unless a new node is brought up in the cluster to host the fourth copy of the shard.

?

6. Noop updates 空更新

When updating a document using the index API a new version of the document is always created even if the document hasn’t changed. If this isn’t acceptable?

use the _update API with detect_noop set to true. This option isn’t available on the index API because the index API doesn’t fetch the old source and isn’

t able to compare it against the new source.

There isn’t a hard and fast rule about when noop updates aren’t acceptable. It’s a combination of lots of factors like how frequently your data source?

sends updates that are actually noops and how many queries per second Elasticsearch runs on the shard receiving the updates.

當通過Index API更新一個文檔時，無論內容有沒有被實際更改，都會創建version。如果這是不可接受的，就要使用_update API,并設置空操作檢測選項（detect_noop）設置成

true.這個選項在index API中不存在，因為index API不會去獲取舊的數據與新的數據比對。

7 Timeout

The primary shard assigned to perform the index operation might not be available when the index operation is executed. Some reasons for this might be that?

the primary shard is currently recovering from a gateway or undergoing relocation. By default, the index operation will wait on the primary shard to become?

available for up to 1 minute before failing and responding with an error. The timeout parameter can be used to explicitly specify how long it waits. Here is?

an example of setting it to 5 minutes:

curl -X PUT "localhost:9200/twitter/_doc/1?timeout=5m" -H 'Content-Type: application/json' -d'

{

? ? "user" : "kimchy",

? ? "post_date" : "2009-11-15T14:12:12",

? ? "message" : "trying out Elasticsearch"

}

'

如果primary出現異常，不能完成索引文檔操作，系統就會等待，默認情況是等待一分鐘，仍然異常就會超時報錯。以上有設置超時時間為5分鐘。

8 Versioning

Each indexed document is given a version number. By default, internal versioning is used that starts at 1 and increments with each update, deletes included.?

Optionally, the version number can be set to an external value (for example, if maintained in a database). To enable this functionality, version_type should?

be set to external. The value provided must be a numeric, long value greater than or equal to 0, and less than around 9.2e+18.

When using the external version type, the system checks to see if the version number passed to the index request is greater than the version of the currently?

stored document. If true, the document will be indexed and the new version number used. If the value provided is less than or equal to the stored document’s?

version number, a version conflict will occur and the index operation will fail. For example:

curl -X PUT "localhost:9200/twitter/_doc/1?version=2&version_type=external" -H 'Content-Type: application/json' -d'

{

? ? "message" : "elasticsearch now has versioning support, double cool!"

}

'

索引文檔版本控制。

每個索引文檔都有個版本號，默認由ES自內部制，從1開始，更新和刪除操作會增加版本序號。

版本也可以由外部系統控制，通過version_type設置為external和給定version值。如果給定的版本號大于當前版本號，會報錯。手動指定版本號的例子如上。