1.3 KiB
@brief ensures that a cap constraint exists
collection.ensureIndex({ type: "cap", size: size, byteSize: byteSize })
Creates a size restriction aka cap for the collection of size
documents and/or byteSize data size. If the restriction is in place
and the (size plus one) document is added to the collection, or the
total active data size in the collection exceeds byteSize, then the
least recently created or updated documents are removed until all
constraints are satisfied.
It is allowed to specify either size or byteSize, or both at
the same time. If both are specified, then the automatic document removal
will be triggered by the first non-met constraint.
Note that at most one cap constraint is allowed per collection. Trying to create additional cap constraints will result in an error. Creating cap constraints is also not supported in sharded collections with more than one shard.
Note that this does not imply any restriction of the number of revisions of documents.
@EXAMPLES
Restrict the number of document to at most 10 documents:
@EXAMPLE_ARANGOSH_OUTPUT{collectionEnsureCapConstraint} ~db._create('examples'); db.examples.ensureIndex({ type: "cap", size: 10 }); for (var i = 0; i < 20; ++i) { var d = db.examples.save( { n : i } ); } db.examples.count(); ~db._drop('examples'); @END_EXAMPLE_ARANGOSH_OUTPUT