Atri Sharma <atri.j...@gmail.com> writes: > One of the factors that leads to bad estimates is that the histogram of the > values of a column maintained by the planner gets old by time and the data > in the column changes. So, the histogram is no longer a quite accurate view > of the data and it leads to bad selectivity.
TBH, this is so far down the list of problems that it'll be a long time before we need to worry about it. It's certainly not the number one priority for any project to model risk in the planner. The thing that I think is probably the number one problem is estimates that depend on an assumption of uniform distribution of sought-after rows among those encountered by a scan. This is usually where bad plans for LIMIT queries are coming from. We could certainly add some sort of fudge factor to those costs, but I'd like to have a more-or-less principled framework for doing so. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers