close [t:4372] Dr. Noga system comment updated. Topics include insertions,...

  }

}

Here's how querying works:

lookups:

    - As of Dr. No, we don't do any tree shaping on lookup.

    - We don't promote eagerly or use aggressive promotion or passive-aggressive 

    promotion.	We just push messages down according to the traditional BRT 

    algorithm on insertions.

    - when a node is brought into memory, we apply ancestor messages above it.

basement nodes, bulk fetch,  and partial fetch:

    - leaf nodes are comprised of N basement nodes, each of nominal size. when

    a query hits a leaf node. it may require one or more basement nodes to be in memory.

    - for point queries, we do not read the entire node into memory. instead,

      we only read in the required basement node

    - for range queries, cursors may return cursor continue in their callback

      to take a shortcut path to the next row in the basement node.

    - for range queries, cursors that prelock a range benefit from 

      internal prefetching of nodes within that range.

      to take a the shortcut path until the end of the basement node.

    - for range queries, cursors may prelock a range of keys (with or without a txn).

      the fractal tree will prefetch nodes aggressively until the end of the range.

    - without a prelocked range, range queries behave like successive point queries.

*/