BIND 10 #1608: implement findAdditional() for in memory data source

[BIND 10 Development]

#1608: implement findAdditional() for in memory data source
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                   Reporter:         |                 Owner:
  jinmei                             |                Status:  new
                       Type:  task   |             Milestone:  Next-Sprint-
                   Priority:  major  |  Proposed
                  Component:  data   |            Resolution:
  source                             |             Sensitive:  0
                   Keywords:         |           Sub-Project:  DNS
            Defect Severity:  N/A    |  Estimated Difficulty:  0
Feature Depending on Ticket:         |           Total Hours:  0
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Comment (by vorner):

 Hello

 I could think of a lazy implementation. All these hint pointers are left
 out as NULL at the beginning (and some kind of flag „precomputed“ is set
 to false). Once the findAdditional is called for the RRset, the flag is
 checked. If it is false, the default ZoneFinder::findAdditional is found
 and the result is stored. If the flag is true, it just returns whatever is
 stored there.

 It has the slight disadvantage that it slows down answers when serving a
 little bit shortly after the startup. But considering most of the queries
 are to the same names, the once-time real lookup should not be visible.

 Also, this might be extended in future when we have some kind of updates
 at runtime. The flag could be turned to generation, all A/AAAA would have
 their generation and if they are not the same, the hint would be
 recomputed.

 But I don't know if we really want to go to the lazy approach, since it is
 slightly more work, if we want to redesign the internal structure anyway.

-- 
Ticket URL: <http://bind10.isc.org/ticket/1608#comment:2>
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