Convert a Collection to Capped
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To convert a non-capped collection to a capped collection, use the convertToCapped
database command.
The convertToCapped command holds a database-exclusive lock for the
duration of the operation. Other operations that lock the same database
are blocked until the convertToCapped operation completes.
About this Task
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 write operations and therefore have worse concurrent insert, update, and delete performance than non-capped collections. Before you create a capped collection, consider if you can use a TTL index instead.
Before you Begin
Create a non-capped collection called log2:
db.createCollection("log2")
Steps
Convert the collection to a capped collection
To convert the log2 collection to a capped collection, run the
convertToCapped command:
db.runCommand( { convertToCapped: "log2", size: 100000 } )
The log2 collection has a maximum size of 100,000 bytes.
Confirm that the collection is capped
To confirm that the log2 collection is now capped, use the
isCapped() method:
db.log2.isCapped()
true