Use a gist index. Easiest way would be to define a box with mindate at one corner and maxdate at the other corner, and then search for point(obsdate,obsdate) that lie with in the box. A more detailed explination is in the archives somewhere... On Sun, Feb 19, 2006 at 08:06:12PM -0800, andrew@xxxxxxxxxxxx wrote: > Here's a simplified version of the schema: > > Table A has an ID field, an observation date, and other stuff. There are about 20K IDs and 3K observations per ID. Table B has a matching ID field, minimum and maximum dates, a code, and other stuff, about 0-50 records per ID. For a given ID, the dates in B never overlap. On A, the PK is (id, obsdate). On B, the PK is (id, mindate). I want > > SELECT a.id, b.code, AVG(other stuff) FROM A LEFT JOIN B ON a.id=b.id AND a.obsdate BETWEEN b.mindate AND b.maxdate GROUP BY 1,2; > > Is there a way to smarten the query to take advantage of the fact at most one record of B matches A? Also, I have a choice between using a LEFT JOIN or inserting dummy records into B to fill in the gaps in the covered dates, which would make exactly one matching record. Would this make a difference? > > Thanks. > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Have you searched our list archives? > > http://archives.postgresql.org > -- Jim C. Nasby, Sr. Engineering Consultant jnasby@xxxxxxxxxxxxx Pervasive Software http://pervasive.com work: 512-231-6117 vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
