Woops! I slipped a digit. My first sentence should say: ... yes, there may be as many as 100,000 alerts per night, hence more than 10^9 events for the lifetime of the survey.
- Kirk ----- Original Message ----- From: Kirk D Borne <[EMAIL PROTECTED]> Date: Thursday, August 17, 2006 7:05 pm Subject: Re: [LSST-data] Re: cpu for queries > To reiterate other people's comments: yes, there may be as many > as 10,000 alerts per night, hence more than 10^8 events for the > lifetime of the survey. It makes sense that one alert > corresponds to one object. But one object may have many > alerts (e.g., a new supernova may be "alerted" for ~100 nights > in a row; or an asteroid may be "alerted" every time it is in > the FOV). > > It is imperative to have the objectid in the alert table. > One can then join on the object table to get the corresponding > object information. But I don't see that the converse is > equally useful --> i.e., having the alertid (for *each* alert) > in the object table. However, I do like Ani's suggestion of > having the most recent alert's alertid in the object table. > > - Kirk > > ----- Original Message ----- > From: Ani Thakar <[EMAIL PROTECTED]> > Date: Thursday, August 17, 2006 1:03 pm > Subject: Re: [LSST-data] Re: cpu for queries > > > > > i agree with maria that there doesnt need to be a separate table > > to map > > objectid<->alertid, but it may be useful/convenient to keep the > > first or > > last alertid for each object in the object table, so for example > > users > > can query on whether an object has ever had an alert or the last > > alert > > for an object. if this is not a useful science question then > > alertid > > doesnt need to be in the object table, only objectid in the > alert > > table. > > ani > > > > On Thu, 17 Aug 2006, Tim Axelrod wrote: > > > > > Jacek, > > > > > > I will look it up later (I am on a telecon), but my memory is > > that the > > > alert rate is about 100,000 per night, not 10! > > > > > > An alert should apply only to a single object. > > > > > > Tim > > > > > > Jacek Becla wrote: > > > > > > > Maria, > > > > > > > >> Can an alert correspond to more than one object? > > > >> > > > >> Probably not. Then you don't need a new table only and > > objectID in > > > >> the Alert table > > > > > > > > > > > > That would work if the answer is 'no', especially given > > > > that the Alert table will be compact. (Can someone remind > > > > me how many alerts we expect per night? Assuming 10, > > > > the Alert table will be growing 3,000 rows/year, > > > > that is nothing.) > > > > We should then keep the bit in the Object table > > > > indicating whether there was an alert for given Object > > > > (as Tim suggested) > > > > > > > > thanks, > > > > Jacek > > > > -- > > Aniruddha R. Thakar, Research Scientist > > Center for Astrophysical Sciences, JHU, Bloomberg 375 > > 3701 San Martin Drive, Baltimore MD 21218-2695 > > 410-516-4850, Fax: 410-516-5096 > > [EMAIL PROTECTED], http://www.sdss.jhu.edu/~thakar > > ----------------------------------------------------------------- > -- > > ---- > > When I was a boy I was told that anybody could become President; > > I'm > > beginning to believe it. [Clarence Darrow] > > > > _______________________________________________ > > LSST-data mailing list > > [email protected] > > http://www.lsstmail.org/mailman/listinfo/lsst-data > > > _______________________________________________ LSST-data mailing list [email protected] http://www.lsstmail.org/mailman/listinfo/lsst-data
