Detecting Expired Documents in Result Sets: If you are using views for indexing items from Couchbase Server, items that have not yet been removed as part of the expiry pager maintenance process will be part of a result set returned by querying the view. To exclude these items from a result set you should use query parameter include_doc set to true. This parameter typically includes all JSON documents associated with the keys in a result set. For example, if you use the parameter include_docs=true Couchbase Server will return a result set with an additional "doc" object which contains the JSON or binary data for that key:

{"total_rows":2,"rows":[
{"id":"test","key":"test","value":null,"doc":{"meta":{"id":"test","rev":"4-0000003f04e86b040000000000000000","expiration":0,"flags":0},"json":{"testkey":"testvalue"}}},
{"id":"test2","key":"test2","value":null,"doc":{"meta":{"id":"test2","rev":"3-0000004134bd596f50bce37d00000000","expiration":1354556285,"flags":0},"json":{"testkey":"testvalue"}}}
]
}

For expired documents if you set include_doc=true, Couchbase Server will return a result set indicating the document does not exist anymore. Specifically, the key that had expired but had not yet been removed by the cleanup process will appear in the result set as a row where "doc":null:

{"total_rows":2,"rows":[
{"id":"test","key":"test","value":null,"doc":{"meta":{"id":"test","rev":"4-0000003f04e86b040000000000000000","expiration":0,"flags":0},"json":{"testkey":"testvalue"}}},
{"id":"test2","key":"test2","value":null,"doc":null}
]
}

Reduces and Expired Documents: In some cases, you may want to perform a reduce function to perform aggregations and calculations on data in Couchbase Server 2.0. In this case, Couchbase Server takes pre-calculated values which are stored for an index and derives a final result. This also means that any expired items still on disk will be part of the reduction. This may not be an issue for your final result if the ratio of expired items is proportionately low compared to other items. For instance, if you have 10 expired scores still on disk for an average performed over 1 million players, there may be only a minimal level of difference in the final result. However, if you have 10 expired scores on disk for an average performed over 20 players, you would get very different result than the average you would expect.

In this case, you may want to run the expiry pager process more frequently to ensure that items that have expired are not included in calculations used in the reduce function. We recommend an interval of 10 minutes for the expiry pager on each node of a cluster. Do note that this interval will have some slight impact on node performance as it will be performing cleanup more frequently on the node.