On 5 September 2015 at 20:46, Bruce Momjian <br...@momjian.us> wrote:
> On Fri, Aug 28, 2015 at 05:33:34PM +0900, Kyotaro HORIGUCHI wrote: > > Hello, this patch enables planner to be couscious of inter-column > > correlation. > > > > Sometimes two or more columns in a table has some correlation > > which brings underestimate, which leads to wrong join method and > > ends with slow execution. > > > > Tomas Vondra is now working on heavily-equipped multivariate > > statistics for OLAP usage. In contrast, this is a lightly > > implemented solution which calculates only the ratio between a > > rows estimated by current method and a actual row number. I think > > this doesn't conflict with his work except the grammar part. > > I am very glad multi-variate statistics are being addressed. I think > this is our most common cause of optimizer failures. > Glad to see you agree. Why have you said this on *this* patch, when Tomas' patch has been very obviously addressing this problem since January, with very little traction. Please add your backing to Tomas' patch. -- Simon Riggs http://www.2ndQuadrant.com/ <http://www.2ndquadrant.com/> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
