dbHash

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定义
兼容性
语法
命令字段
行为
Return Document
示例

定义

dbHash: Returns the hash values of the collections in a database and an MD5 value for these collections. dbHash is useful to compare databases across mongod instances, such as across members of replica sets.

警告

The dbHash command obtains a shared (S) lock on the database, which prevents writes until the command completes.

兼容性

此命令可用于以下环境中托管的部署：

MongoDB Atlas：用于云中 MongoDB 部署的完全托管服务

重要

M0、M2、M5 和 Flex 集群或无服务器实例不支持此命令。有关更多信息，请参阅不支持的命令。

MongoDB Enterprise：基于订阅、自我管理的 MongoDB 版本
MongoDB Community：源代码可用、免费使用且可自行管理的 MongoDB 版本

语法

该命令具有以下语法：

db.runCommand(
   {
     dbHash: 1,
     collections: [ <collection1>, ... ]
   }
)

命令字段

该命令接受以下字段：

字段	类型	说明
`dbHash`	Any type	The command to run. Specify any value.
`collections`	阵列	Optional. An array of collection names. Either specify the collections for which to return the hash values, or omit or specify an empty array to return the hash values for all collections in the database.

行为

Non-Existent Collection

If a collection in the collections array is non-existent, dbHash does not return a hash value for that collection.

限制

The dbHash command no longer support afterClusterTime. As such, dbHash cannot be associated with causally consistent sessions.

Return Document

The command returns a document with the following fields:

字段

说明

host

The host and port of the mongod instance on which the command is run.

collections

A document with the collections and their corresponding hash values.

{
   <collection1>: <hash1>,
   <collection2>: <hash2>,
   ...
}

capped

An array that lists the capped collections.

uuids

A document with the collections and their corresponding UUID values.

{
   <collection1>: <UUID1>,
   <collection2>: <UUID2>,
   ...
}

md5

The aggregate hash value for these collections.

timeMillis

Number of milliseconds to generate the hash.

ok
operationTime
$clusterTime

Returned with every command. See also 响应 for details.

示例

Return Hash Values for All Collections in a Database

The following example returns the hash value for all collections in the database test:

use test
db.runCommand( { dbHash: 1 } )

该操作将返回以下文档：

{
   "host" : "myHostName.local:27017",
   "collections" : {
      "foo" : "d27b769230edc551d869060ec3fb68bd",
      "inventory" : "ec3d821581ea1bd3aa8196c94b946874",
      "log" : "d41d8cd98f00b204e9800998ecf8427e",
      "orders" : "0242c0a128c284ea9576a34db2306c12",
      "restaurants" : "5dc9b88091c36f0d529567b5b6e3fc92",
      "zipcodes" : "31ede812bf397509a87359c65bf2a08c"
   },
   "capped" : [
      "log"
   ],
   "uuids" : {
      "foo" : UUID("469592fe-3bfe-425e-975f-cedbe0c4741d"),
      "inventory" : UUID("0830e0ad-cc24-4fc7-80d0-8e22fe45e382"),
      "log" : UUID("4be024ff-711b-4ab8-836b-dee662e090f1"),
      "orders" : UUID("755be489-745f-400c-ac3b-f27525ad0108"),
      "restaurants" : UUID("520b56ec-3276-4904-b6e5-286bc9bfa648"),
      "zipcodes" : UUID("12e97b70-c174-40af-a178-5d83a241fe20")
   },
   "md5" : "0cb7417ae9d9eb865000b4debdc671da",
   "timeMillis" : 53,
   "ok" : 1,
   "operationTime" : Timestamp(1529208582, 4),
   "$clusterTime" : {
      "clusterTime" : Timestamp(1529208582, 4),
      "signature" : {
         "hash" : BinData(0,"X3MmevDqUgCVvN1AhnT+fiOL/Lc="),
         "keyId" : NumberLong("6567898567824900097")
      }
   }
}

Return Hash Values for Specified Collections in a Database

The following example returns the hash value for the collections inventory and orders in the database test:

use test
db.runCommand( { dbHash: 1, collections: [ "inventory", "orders" ] } )

该操作将返回以下文档：

{
   "host" : "myHostName.local:27017",
   "collections" : {
      "inventory" : "ec3d821581ea1bd3aa8196c94b946874",
      "orders" : "0242c0a128c284ea9576a34db2306c12"
   },
   "capped" : [ ],
   "uuids" : {
      "inventory" : UUID("0830e0ad-cc24-4fc7-80d0-8e22fe45e382"),
      "orders" : UUID("755be489-745f-400c-ac3b-f27525ad0108")
   },
   "md5" : "cb4676f316ff2ff29c701a5edd18afe3",
   "timeMillis" : 0,
   "ok" : 1,
   "operationTime" : Timestamp(1529208801, 1),
   "$clusterTime" : {
      "clusterTime" : Timestamp(1529208801, 1),
      "signature" : {
         "hash" : BinData(0,"I4z4a4Mgs+tcx0MP5xIU8DYAMB0="),
         "keyId" : NumberLong("6567898567824900097")
      }
   }
}

后退

数据大小

来年

dbStats