* Add benchmark case for many-to-one join Signed-off-by: Bryan Boreham <bjboreham@gmail.com> * query_range: compute join signatures just once For an expression like `a + on(p,q) b`, extract the `p,q` part from each series once, instead of re-computing at every step of the range. Although there was a cache, computing the key by concatenating all labels was expensive. Signed-off-by: Bryan Boreham <bjboreham@gmail.com>