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Change Maximum Documents in a Capped Collection

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New in version 6.0.

To change the maximum number of documents in a capped collection, use the collMod command's cappedMax option.

  • If cappedMax is less than or equal to 0, there is no maximum document limit.

  • If cappedMax is less than the current number of documents in the collection, MongoDB removes the excess documents on the next insert operation.

Generally, TTL (Time To Live) indexes offer better performance and more flexibility than capped collections. TTL indexes expire and remove data from normal collections based on the value of a date-typed field and a TTL value for the index.

Capped collections serialize inserts and therefore have worse concurrent insert performance than non-capped collections. Before you create a capped collection, consider if you can use a TTL index instead.

Create a capped collection called log that can store a maximum of 20,000 documents:

db.createCollection( "log", { capped: true, size: 5242880, max: 20000 } )

Run the following command to set the maximum number of documents in the log collection to 5,000:

db.runCommand( { collMod: "log", cappedMax: 5000 } )
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