Extremely large indexes require more than one physical partition. If more than one partition exists, each partition is queried individually and the results merged for presentation to the end-user. The mergeSettings attribute works together with responseNumberSettings to control the number of results returned from a merged result set.
The responseNumberSettings attribute (see the ResponseNumber Settings section in this chapter) determines how many results are returned from each partition. The mergeSettings attribute determines how many of those total results are returned to the end user. If you use mergeSettings, be sure to set it to a higher number than the responseNumberSettings. For instance, if you return 50 results from each of four partitions, you may use mergeSettings to trim the combined result list to the top 100 results, but not the top 20 results; it is more efficient to trim the responseNumberSettings to begin with than to do so after merging.
The mergeSettings attribute uses the same parameters described in ResponseNumber Settings. It is included in all request types except for the ViewDocumentRequest. If mergeSettings is not set, responseNumberSettings is used instead.
