Keywords: DataAccWG Hi all,
We will have a Database telecon this Friday at 11:00 AM PDT. I'd like to go over the latest disk io numbers. Here is the latest version: http://www.slac.stanford.edu/~becla/tmp/lsst_diskIO_estimates_v04.doc http://www.slac.stanford.edu/~becla/tmp/lsst_diskIO_estimates_v04.xls Shortly speaking the numbers looks very reasonable for everything except two temporal queries, and both have the same problem (see below) Phone number: 866 330 1200 Pass code: 300 2363 Jacek ====================== Select time series data for given cone: SELECT o.objectId, o.ra, o.dec, i.MJD, d.* FROM Object o, CCDImage i, DIASource d WHERE o.ra BETWEEN ra1 + cos(decl1)*(0.5) AND ra1 - cos(decl1)*(0.5) AND o.decl between decl1 +0.5 and decl1 - 0.5 AND o.objectId = d.objectId AND d.ccdImageId = i.ccdImageId ORDER BY o.objectId, i.MJD ASC Object table: 10 million rows (one partition) DIASource table: 45 billion rows CCDImage table: 135 million rows At the moment, if I assume a modest 1% selectivity for ra,dec that gives 10K rows from Object table. Join with DIASource (5 DIASources per star) gives 50K rows, then join with CCDImage (assuming 10K DIASources per CCDImage) gives 50*10^12 rows. That is over a petabyte, which now needs to be sorted, then for each row we need to fetch full DIASource row.... _______________________________________________ LSST-data mailing list [email protected] http://www.lsstmail.org/mailman/listinfo/lsst-data
