MB-17382: Expand bounding box on subsequent calls

There can be several flushes of the KVs during the initial indexing.
Make sure the bounding box is calculated for the whole data set and
not just the current call.

Change-Id: I1d4e7f544a981a047d26cb2fe7e70116b57c86ac
Reviewed-on: http://review.couchbase.org/58692
Reviewed-by: Abhishek Singh <abhishek@couchbase.com>
Tested-by: Volker Mische <volker.mische@gmail.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>

gc-couchbase/src/spatial_view.erl

@@ -80,7 +80,8 @@ write_kvs(Group, TmpFiles0, ViewKVs) ->
         fun({#set_view{id_num = Id}, KvList}, {AccCount, TmpFiles}) ->
             TmpFileInfo0 = dict:fetch(Id, TmpFiles),
             Mbb = calc_mbb(KvList),
-            TmpFileInfo = TmpFileInfo0#set_view_tmp_file_info{extra = Mbb},
+            Mbb2 = merge_mbbs(Mbb, TmpFileInfo0#set_view_tmp_file_info.extra),
+            TmpFileInfo = TmpFileInfo0#set_view_tmp_file_info{extra = Mbb2},
 
             KvBins = convert_primary_index_kvs_to_binary(KvList, Group, []),
             ViewRecords = lists:foldr(
@@ -112,6 +113,19 @@ calc_mbb(KvList) ->
     end, nil, KvList).
 
 
+-spec merge_mbbs([[number()]] | nil, [[number()]] | nil) -> [[number()]] | nil.
+merge_mbbs(nil, MbbB) ->
+    MbbB;
+merge_mbbs(MbbA, nil) ->
+    MbbA;
+merge_mbbs(MbbA, MbbB) ->
+    Less = fun(A, B) -> A < B end,
+    lists:map(fun({[MinA, MaxA], [MinB, MaxB]}) ->
+        [vtree_util:min({MinA, MinB}, Less),
+         vtree_util:max({MaxA, MaxB}, Less)]
+    end, lists:zip(MbbA, MbbB)).
+
+
 % Convert the key from a list of 2-tuples to a list of raw doubles
 % NOTE vmx 2014-12-12: The first case could be more efficient, but for now
 % it's good enough. Once the enclosing MBB for the initial index build is