mget(批量查询)

一、介绍

mget是es提供的一种批量的读取操作的API。

mget API允许根据索引，类型（可选）和id（以及可能的路由）获取多个文档。响应包括一个docs数组。该数组具有与原始多重获取请求相对应的所有提取文档（如果特定的get失败，则在响应中包含包含此错误的对象）。成功获取的结构与get API提供的文档的结构相似。

二、示例用法

2.1 测试数据准备

示例索引结构如下

PUT example PUT example/docs/_mapping { "properties": { "id": {"type": "long"}, "name": {"type": "text"}, "counter": {"type": "integer"}, "tags": {"type": "text"} } } PUT example/docs/1 { "id": 1, "name": "admin", "counter": 1, "tags": ["gray"] } PUT example/docs/2 { "id": 2, "name": "zhangsan", "counter": 1, "tags": ["black"] } PUT example/docs/3 { "id": 3, "name": "lisi", "counter": 1, "tags": ["purple"] } PUT example_test PUT example_test/docs/_mapping { "properties": { "id": {"type": "long"}, "name": {"type": "text"}, "counter": {"type": "integer"}, "tags": {"type": "text"} } } PUT example_test/docs/1 { "id": 1, "name": "test-admin", "counter": 1, "tags": ["gray"] } PUT example_test/docs/2 { "id": 2, "name": "test-zhangsan", "counter": 1, "tags": ["black"] } PUT example_test/docs/3 { "id": 3, "name": "test-lisi", "counter": 1, "tags": ["purple"] } #查询example所有数据 GET example/docs/_search { "query": { "match_all": {} } } #查询example_test所有数据 GET example_test/docs/_search { "query": { "match_all": {} } }

2.2 传统的单条查询，在面对需要查询多个时，需要一次次发送请求到es

示例查询

GET example/docs/1 GET example/docs/2 GET example_test/docs/1 GET example_test/docs/2

这样其实局限性，多次的网络请求很容易造成资源浪费和降低性能。

2.3 mget之查询（index不同）

示例如下

GET _mget { "docs": [ { "_index": "example", "_type": "docs", "_id": "1" }, { "_index": "example", "_type": "docs", "_id": "2" }, { "_index": "example_test", "_type": "docs", "_id": "1" }, { "_index": "example_test", "_type": "docs", "_id": "2" } ] }

返回数据如下

{ "docs": [ { "_index": "example", "_type": "docs", "_id": "1", "_version": 1, "found": true, "_source": { "id": 1, "name": "admin", "counter": 1, "tags": [ "gray" ] } }, { "_index": "example", "_type": "docs", "_id": "2", "_version": 1, "found": true, "_source": { "id": 2, "name": "zhangsan", "counter": 1, "tags": [ "black" ] } }, { "_index": "example_test", "_type": "docs", "_id": "1", "_version": 1, "found": true, "_source": { "id": 1, "name": "test-admin", "counter": 1, "tags": [ "gray" ] } }, { "_index": "example_test", "_type": "docs", "_id": "2", "_version": 1, "found": true, "_source": { "id": 2, "name": "test-zhangsan", "counter": 1, "tags": [ "black" ] } } ] }

2.4 mget之查询（index相同，type不同）

不建议掌握，type有可能在后续的版本废除。这里只做一下简单示例。

GET _mget { "docs": [ { "_index": "example", "_type": "docs1", "_id": "1" }, { "_index": "example", "_type": "docs2", "_id": "1" }, ]

2.5 mget之查询（index相同，type相同）。

示例如下

GET _mget { "docs": [ { "_index": "example", "_type": "docs", "_id": "1" }, { "_index": "example", "_type": "docs", "_id": "2" }, { "_index": "example", "_type": "docs", "_id": "3" } ] } #index和type相同的话可以简化成如下 GET example/docs/_mget { "docs": [ { "_id": "1" }, { "_id": "2" }, { "_id": "3" } ] }

返回结果

{ "docs": [ { "_index": "example", "_type": "docs", "_id": "1", "_version": 1, "found": true, "_source": { "id": 1, "name": "admin", "counter": 1, "tags": [ "gray" ] } }, { "_index": "example", "_type": "docs", "_id": "2", "_version": 1, "found": true, "_source": { "id": 2, "name": "zhangsan", "counter": 1, "tags": [ "black" ] } }, { "_index": "example", "_type": "docs", "_id": "3", "_version": 1, "found": true, "_source": { "id": 3, "name": "lisi", "counter": 1, "tags": [ "purple" ] } } ] }

mget是很重要的，一般来说，进行查询的时候，如果一次性查询多条数据的话，那么一定要用batch批量操作的api，尽可能减少网络开销次数，可以将性能大幅度提升。

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