ADQL XMATCH

[Walter Landry]

Marco Molinaro <molinaro at oats.inaf.it> wrote:
> However, to have a simple distance estimator available quickly in
> ADQL, we cannot work on more complex solutions in v2.1 (it's a minor),
> so a proposal was to bend towards a DISTANCE(ra1,dec1,ra2,dec2) <
> radius solution.
> Apart from skipping the complex scenario cross match, this one _only_
> the drawback that we need to understand how to work or work-around the
> overload in ADQL since DISTANCE(<POINT>,<POINT>) already exists.
> (and maybe clearly define whether we need to keep only this one, not
> to skip epoch issues).

Since no one commented on it before, I would like to repeat my
proposal for a point literal.

  {a,b} -> POINT('ICRS GEOCENTER',a,b)

Then the distance function would be

  DISTANCE({ra1,dec1},{ra2,dec2})

This would keep the function type safe and obviate the need for a new
overload for DISTANCE.

Cheers,
Walter Landry