In the current version of IxSet, the performance of querying on just
the Lon would be essentially the same as if you just had a "Data.Map
Lon Point". But the queries on the second index are current not so
great. There is work in progress to rewrite the internals of IxSet to
be based on a kd-tree, in which case your query should be pretty
efficient.
So, that answer is pretty vague :) I am in the process of wrapping up
happstack 0.6 which has focused on fixing some performance issues with
happstack-server, and refactoring the code so that user API and
internals are more clearly separated and better documented.
happstack 0.7 is all about happstack-state. A key aspect will be
nailing down some solid performance benchmarks instead of vague hand
waving :)
The numbers you give are certainly within the scope of what we would
like 0.7 to be able to handle. Also, I should note that
happstack-state and happstack-ixset are independent from each other.
You can easily use something other than IxSet to store your points and
still use happstack-state.
- jeremy
On Fri, Oct 1, 2010 at 1:53 PM, Thomas M. DuBuisson
That is pretty close to how it would look using happstack-state. Here is a complete, runnable example which defines the types, a query, creates/initializes the database, performs the query, and prints the results. [snip]
How is data stored in Happstack.State? I see the "Component" instance uses "fromList" from happstack-ixset but can't find any information on the algorithm used or its efficiency (computationally or wrt space).
If making this more concrete helps then here is a possible use:
== GPS Points == I have a GPS logger that logs every 10 seconds when I jog. Jogging for an hour a day for the past 180 days has resulted in 64k points. Pretending I hosted a site for joggers (and all points were in the same DB) I could easily result in a billion points (< 20K users). Would happstack-ixset code in the form "points @< (Lon -120) @> (Lon -125) @> (Lat 45) @< (Lat 50)" perform reasonably?
Cheers, Thomas