减少MongoDB数据库文件大小 [英] Reducing MongoDB database file size

问题描述

我有一个曾经很大(> 3GB)的MongoDB数据库.从那时起，文档已被删除，我期望数据库文件的大小会相应减小.

I've got a MongoDB database that was once large (>3GB). Since then, documents have been deleted and I was expecting the size of the database files to decrease accordingly.

但是由于MongoDB保留分配的空间，因此文件仍然很大.

But since MongoDB keeps allocated space, the files are still large.

我在这里和那里读到，管理命令mongod --repair用于释放未使用的空间，但是磁盘上没有足够的空间来运行此命令.

I read here and there that the admin command mongod --repair is used to free the unused space, but I don't have enough space on the disk to run this command.

您知道我可以释放未使用空间的方法吗?

Do you know a way I can freed up unused space?

推荐答案

更新:使用compact命令和 WiredTiger，它看起来像

UPDATE: with the compact command and WiredTiger it looks like the extra disk space will actually be released to the OS.

更新:从v1.9 +开始，存在 compact 命令.

UPDATE: as of v1.9+ there is a compact command.

此命令将执行在线压缩".它仍然需要一些额外的空间，但并不需要那么多.

This command will perform a compaction "in-line". It will still need some extra space, but not as much.

MongoDB通过以下方式压缩文件:

MongoDB compresses the files by:

• 将文件复制到新位置
• 循环浏览文档并重新排序/重新解决它们
• 用新文件替换原始文件

您可以通过运行mongod --repair或直接连接并运行db.repairDatabase()来执行此压缩"操作.

You can do this "compression" by running mongod --repair or by connecting directly and running db.repairDatabase().

无论哪种情况，您都需要在某个地方复制文件.现在，我不知道为什么您没有足够的空间来执行压缩，但是，如果您有另一台计算机具有更多的空间，那么您确实可以选择.

In either case you need the space somewhere to copy the files. Now I don't know why you don't have enough space to perform a compress, however, you do have some options if you have another computer with more space.

1. 将数据库导出到安装了Mongo的另一台计算机上(使用mongoexport)，然后可以导入同一数据库(使用mongoimport).这将导致新数据库的压缩程度更高.现在，您可以停止将原来的mongod替换为新的数据库文件，一切顺利.
2. 停止当前mongod，然后将数据库文件复制到更大的计算机上，然后在该计算机上运行修复程序.然后，您可以将新的数据库文件移回原始计算机.

1. Export the database to another computer with Mongo installed (using mongoexport) and then you can Import that same database (using mongoimport). This will result in a new database that is more compressed. Now you can stop the original mongod replace with the new database files and you're good to go.
2. Stop the current mongod and copy the database files to a bigger computer and run the repair on that computer. You can then move the new database files back to the original computer.

当前没有使用Mongo进行紧凑压缩"的好方法.而且Mongo绝对可以占用很多空间.

There is not currently a good way to "compact in place" using Mongo. And Mongo can definitely suck up a lot of space.

目前最好的压缩策略是运行主从设置.然后，您可以压缩从站，让它赶上并切换它们.我知道还是有点毛.也许Mongo团队会提出更好的现场压实度，但我认为这并不在他们的榜单上.当前假定驱动器空间便宜(通常是便宜的).

The best strategy right now for compaction is to run a Master-Slave setup. You can then compact the Slave, let it catch up and switch them over. I know still a little hairy. Maybe the Mongo team will come up with better in place compaction, but I don't think it's high on their list. Drive space is currently assumed to be cheap (and it usually is).

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