On Tue, 2008-02-26 at 10:34 -0500, Tom Lane wrote: > > and add COALESCE(id2,id1) to it as well I think. > > No, because those two expressions are not equivalent. (Hmm ... squint > ... but full merge join is pretty much symmetric, so it's not clear > why it should matter which side is left or right. Maybe COALESCE > isn't > exactly the right concept with which to describe the merged variable?) It is, in this case only, since when id2 is not null id2 == id1. So in this case its OK to express a symmetric relationship as a left handed function. -- Simon Riggs 2ndQuadrant http://www.2ndQuadrant.com ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org/
