blockIterators mechanism does NOT require allocating new cursor

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Another advantage of the new blockIterators iteration mechanism is that it 
actually doesn't require allocating a new cursor for each iterator.  
blockIterators has built-in query isolation, so no need to allocate a new 
cursor for each iterator.  

We could consider NOT allocating a new cursor for the blockIterators 
mechanism; this might make things a little more efficient (no need to keep 
opening and closing cursors for each iterator).

Original issue reported on code.google.com by cjlee...@gmail.com on 11 Sep 2009 at 5:28