ADQL XMATCH

[Walter Landry]

Markus Demleitner <msdemlei at ari.uni-heidelberg.de> wrote:
> Let me support Mark's dislike for failing executable ADQL queries --
> there's the old saying that Unix doesn't keep you from doing stupid
> things because that would keep you from doing clever things.  I've
> found that to be true on several occasions, and I believe the same
> (should be) true of query languages.

You can still do the wrong thing with the two argument version

  DISTANCE({dec,ra},{uploaded.c1,uploaded.c2})

It just gets easier for me to check whether the user is doing the
wrong thing.  We have to do this for our non-SQL back ends because
arbitrary queries will not run.

It also helps the user.  Having a function with the signature

  DISTANCE(POINT,POINT)

is easier for users to accidentally get right than

  DISTANCE(number,number,number,number)

> As to point arguments or split arguments: I'm sure most current
> astronomers will ask for the split-argument version, if only because,
> as Mark points out, almost all current tables are written like that.

With POINT literals, I do not think they would care.

Cheers,
Walter Landry