Cone search slower than similar region query.

[ctslater]

@ebellm reports that the cone search is much slower (~100x) than a region search for 10"-sized areas. I'm guessing this is due to the pandas_udf involved in the cone search; maybe this distance function can get moved into scala to speed up the search?

[zecevicp]

I'll look into this.

[ctslater]

I've been unable to recreate this, using either very big or very small regions. It's true that very small searches are not very efficient (they take similar time as much larger areas), but both cone and region seem to be similarly slow in that regime (in the case of ZTF select * as a worst case scenario, several minutes).