#2711 NORM Trial-3: implement real sorting in the datastore

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#2711: implement real sorting in the datastore
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  Reporter:  tomeu      |       Owner:  bcsaller
      Type:  defect     |      Status:  assigned
  Priority:  normal     |   Milestone:  Trial-3 
 Component:  datastore  |     Version:          
Resolution:             |    Keywords:          
  Verified:  0          |  
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Changes (by bcsaller):

  * status:  new => assigned

Comment:

 There isn't one xapian engine. The reason its done this way is each
 independent backing store has its own indexes and currently they know
 nothing about eachother. We can't even be sure that results included from
 one backingstore (think for example a remote store) will be available by
 the end of a given request.

 The merge is done in the layer that manages many stores. I can look at

 1. making this more efficient
 2. making it send requests to other stores only when the local can't
 satisfy the limit
 3. trying to switch to xapians remote protocol internally

 The first would be simplest, two has all sorts of negiative implications
 and 3 requires alot of change including what amounts to publishing a
 running service per backingstore and allowing in some cases remote access.
 That change couldn't be made lightly.

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Ticket URL: <https://dev.laptop.org/ticket/2711#comment:1>
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