RE: R-tree indexing, RA wrap and LISTENing

[Chris Albertson <chrisalbertson90278@yahoo.com>]

Rob,

I think that's the way to go, create a new data type called
"Sky Coordinate" that is defined as an "RA" and a "DEC"
and then define the types RA and DEC and the operators
that would be required like <, >, +, -, *, "between"
and so on.

Later you define a set of special astrometric operators
over the set of (RA,DEC)  Certainly we'd need a "anglar dstance"
maybe a "precess" operator, The more functions you can add
to the database the more powerfull the querries can be.
You could even define "constellation" that returns the name
of the constallation that a given (RA, DEC) falls into
so you'd be able to querry on "all stars in Orion with mag < 6"
or whatever.
 
Think carfully before signing up for e-mail notifications.
If someone impoorts 15 million observation pairs it could trigger
a real flood of e-mail.  I would want something that insures no
more then say one e-mail an hour no matter how many hits.


--- "Creager, Robert S" <CreagRS@LOUISVILLE.STORTEK.COM> wrote:
> 
> 
> > -----Original Message-----
> > From: Doug Welch [mailto:welch@physics.mcmaster.ca] 
> > Subject: R-tree indexing
> > 
> > Two questions:
> > 
> > 1) Is R-tree indexing being used on coordinate boxes of type 
> > box? If not, this would be a superb idea since R-tree indexed 
> > coordinate box queries (overlap, contained-within, etc) are 
> > viciously efficient and PostgreSQL implements this index.
> 
> I'm using B-Tree indexes to manage my RA/Dec searches, and it works
> quite
> well.  My query uses circle_contains_pt, but I've also bound the
> RA/DEC by
> using BETWEEN.  I may have to take a look at this.  Maybe I can do
> away with
> the BETWEEN.
> 
> Any thoughts on how to handle the stars that sit at 0 RA (or very
> close)?
> I've been toying with creating a new PostgreSQL type which manages
> this wrap
> automatically, but only got a very little way into that one.
> 
> > 
> > 2) Is anyone considering implementing an "alert" query which 
> > would be triggered by a object being added outside previous 
> > object positions (if they exist for that part of the sky) 
> > and/or not in the Tycho list? This would be a way of 
> > detecting moving objects, flare stars, novae, etc.
> 
> PostgreSQL has NOTIFY/LISTEN, which is used for just this purpose.  A
> set of
> NOTIFY events would be created, and folks could sign up to receive
> e-mail of
> these events.  Then the LISTEN would query the dB to see who wanted
> notification, and then send e-mail.
> 
> > 
> > Cheers,
> > Doug
> > 
> 
> Later,
> Rob
> 


=====
Chris Albertson
  Home:   310-376-1029  chrisalbertson90278@yahoo.com
  Cell:   310-990-7550
  Office: 310-336-5189  Christopher.J.Albertson@aero.org
  KG6OMK

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