mergeChunks

項目一覧

定義
互換性
構文
コマンドフィールド
アクセス制御
動作
Return Messages

定義

mergeChunks: For a sharded collection, mergeChunks combines contiguous チャンク ranges on a shard into a single chunk. Issue the mergeChunks command on the admin database from a mongos instance.

互換性

このコマンドは、次の環境でホストされている配置で使用できます。

MongoDB Atlas はクラウドでの MongoDB 配置のためのフルマネージドサービスです

重要

このコマンドはサーバーレスインスタンスではサポートされていません。詳細については、「サポートされていないコマンド」を参照してください。

MongoDB Enterprise: サブスクリプションベースの自己管理型 MongoDB バージョン
MongoDB Community: ソースが利用可能で、無料で使用できる自己管理型の MongoDB のバージョン

構文

このコマンドの構文は、次のとおりです。

db.adminCommand(
   {
     mergeChunks: <namespace>,
     bounds : [
       { <shardKeyField>: <minFieldValue> },
       { <shardKeyField>: <maxFieldValue> }
     ]
   }
)

For compound shard keys, you must include the full shard key in the bounds specification. For example, if the shard key is { x: 1, y: 1 }, mergeChunks has the following form:

db.adminCommand(
   {
     mergeChunks: <namespace>,
     bounds: [
       { x: <minValue>, y: <minValue> },
       { x: <maxValue>, y: <maxValue> }
     ]
   }
 )

コマンドフィールド

このコマンドは、次のフィールドを使用します。

フィールド	タイプ	説明
`mergeChunks`	namespace	The fully qualified namespace of the コレクション where both chunks exist. Namespaces take form of `<database>.<collection>`.
`bounds`	配列	An array that contains the minimum and maximum key values of the new chunk.

アクセス制御

On deployments running with authorization, the built-in role clusterManager provides the required privileges.

動作

注意

Use the mergeChunks only in special circumstances. For instance, when cleaning up your シャーディングされたクラスター after removing many documents.

In order to successfully merge chunks, the following must be true:

In the bounds field, <minkey> and <maxkey> must correspond to the lower and upper bounds of the chunks to merge.
The chunks must reside on the same shard.
The chunks must be contiguous.

mergeChunks returns an error if these conditions are not satisfied.

Return Messages

On success, mergeChunks returns this document:

{
  "ok" : 1,
  "$clusterTime" : {
     "clusterTime" : Timestamp(1510767081, 1),
     "signature" : {
         "hash" : BinData(0,"okKHD0QuzcpbVQg7mP2YFw6lM04="),
         "keyId" : NumberLong("6488693018630029321")
      }
  },
  "operationTime" : Timestamp(1510767081, 1)
}

Another Operation in Progress

mergeChunks returns the following error message if another metadata operation is in progress on the chunks collection:

errmsg: "The collection's metadata lock is already taken."

If another process, such as balancer process, changes metadata while mergeChunks is running, you may see this error. You can retry the mergeChunks operation without side effects.

Chunks on Different Shards

If the input chunks are not on the same シャード, mergeChunks returns an error similar to the following:

{
  "ok" : 0,
  "errmsg" : "could not merge chunks, collection test.users does not contain a chunk ending at { username: \"user63169\" }",
  "$clusterTime" : {
     "clusterTime" : Timestamp(1510767081, 1),
     "signature" : {
         "hash" : BinData(0,"okKHD0QuzcpbVQg7mP2YFw6lM04="),
         "keyId" : NumberLong("6488693018630029321")
      }
  },
  "operationTime" : Timestamp(1510767081, 1)
}

Noncontiguous Chunks

If the input chunks are not contiguous, mergeChunks returns an error similar to the following:

{
  "ok" : 0,
  "errmsg" : "could not merge chunks, collection test.users has more than 2 chunks between [{ username: \"user29937\" }, { username: \"user49877\" })"
  "$clusterTime" : {
     "clusterTime" : Timestamp(1510767081, 1),
     "signature" : {
         "hash" : BinData(0,"okKHD0QuzcpbVQg7mP2YFw6lM04="),
         "keyId" : NumberLong("6488693018630029321")
      }
  },
  "operationTime" : Timestamp(1510767081, 1)
}

戻る

moveRange

refineCollectionShardKey