How to shrink index of partly cleaned mongodb collection?

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Description

Hi there!
I have a mongodb related question.
We use Detailed Read Receipts (Admin UI - Message - Detailed Read Receipts) and collection rocketchat_message_read_receipt is about 2/3 of whole our mongodb size.
We decided to store only one month read receipts and I cleared that collection to only most recent read receipts are retain in db
I did it with command
db.rocketchat_message_read_receipt.remove( { ts: { $lte: ISODate("2021-04-14T08:58:00.000Z") } } )

Now I have much less size of that collection, but still same (15Gb) size of indexes of that collection

How can I clean that indexes?
reIndex is not recommdended for replica set deployments like RocketChat

Before

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After
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Here said that mongo handles that task, but it’s not true. Index size is still same

Server Setup Information

  • Version of Rocket.Chat Server: 3.14.0
  • Operating System: CentOS7
  • Deployment Method: docker
  • Number of Running Instances: 26
  • DB Replicaset Oplog: Enabled
  • NodeJS Version: 12.22.1
  • MongoDB Version: 4.0.24 WiredTiger
  • Proxy: nginx + HAProxy
  • Firewalls involved: No

Any additional Information

Thread at open server

1 Like
2

Partly solution for our situation is to drop indexes with db.rocketchat_message_read_receipt.dropIndexes()
That cleaned all indexes but main _id index.
Better then nothing

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2 Likes