mongodb 怎麼合併多個 database

Question

現在一個實例裡有 DBA, DBB, DBC, NewDB，如何把ABC匯入到NewDB？
結構是一樣的，試過For Insert 和 InsertMany，但是資料有接近500W，插了沒幾條就不工作了。而且效率太低。
請問有什麼高效率的辦法嗎？

Answer 1

如果是複製集的話倒是有辦法，不是十分直觀不過我們有renameCollection Command:
注意：務必讀完上面的連結再動手。

{ renameCollection: "<source_namespace>", to: "<target_namespace>", dropTarget: <true|false> }

Field	Type	Description
renameCollection	string	The namespace of the collection to rename. The namespace is a combination of the database name and the name of the collection.
to	string	The new namespace of the collection. If the new namespace specifies a different database, the renameCollection command copies the collection to the new database and drops the source collection.
dropTarget	boolean	Optional. If true, mongod will drop the target of renameCollection prior to renaming the collection. The default value is false.

Example:

use admin
db.runCommand( { renameCollection: "DBA.xxx", to: "NewDB.xxx" } )
db.runCommand( { renameCollection: "DBA.yyy", to: "NewDB.yyy" } )
...