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CouchbaseView-创新互联

Couchbase index: called view -- virtually another document build via map-reduce function

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  • Map function:
       Call emit() to generate a key-value pair

  • Reduce function:
       Optional (disabled by reduce=false)
       Used to calculate count, sum etc

Query View:

  • Call ViewResult.success() to check whether view execution is successful. Call ViewResult.error()  to see error details

  • Set ViewQuery.debug(true) generate statistics information. Retrieved by  ViewResult.debug()

  • Remember to call ViewQuery.development(true) if a development View has not been published as production view

  • For dev mode, full design doc name is:   _design/dev_[designdoc name],  to query it, just use designdoc name
       If you specify  designdoc name as dev_xxx, you get error:
       com.couchbase.client.java.error.ViewDoesNotExistException: View does not exist
       If you specify designdoc name as  /dev_xxx or  _design/dev_xxx, you get error:
       {"error":"bad_request","reason":"p_w_uploads not supported in Couchbase"}

  • To query composite key, do not use ViewQuery.key(String),  which causes additional quote to be added to the key, add get a json format error:
        invalid UTF-8 JSON  {error,garbage_after_value}
    Uses ViewQuery.key(JsonArray) and JsonArray.from(Object[] array). Each element of array must of correct type (String or Long)

  • To view complete query as url parameter after encoding:  use ViewQuery.toString()

  • Suppose a view composes of 3 field [a, b, c],  it is possible to find documents by  [a, b] only and [a, c] only using that view.  ViewQuery.startKey([a, b, null])  and ViewQuery.startKey([a, null, c])

  • Sort query result:  ViewQuery.desc()

  • References:
    http://docs.couchbase.com/admin/admin/Views/views-writing.html
    http://docs.couchbase.com/admin/admin/Views/views-querySample.html

Bulk operations:

  • Couchbase java sdk supports bulk operation, which improves performance for read/write for a number of documents

  • References:
    http://docs.couchbase.com/developer/java-2.1/documents-bulk.html

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