Bruce Momjian wrote: > OK, based on reports I have seen, generally stats_query_string adds 50% > to the total runtime of a "SELECT 1" query, and the patch reduces the > overhead to 25%.
that is actually not true for both of the platforms(a slow OpenBSD 3.9/x86 and a very fast Linux/x86_64) I tested on. Both of them show virtually no improvement with the patch and even worst it causes considerable (negative) variance on at least the Linux box. > > However, that 25% is still much too large. Consider that "SELECT 1" has > to travel from psql to the server, go through the > parser/optimizer/executor, and then return, it is clearly wrong that the > stats_query_string performance hit should be measurable. > > I am actually surprised that so few people in the community are > concerned about this. While we have lots of people studying large > queries, these small queries should also get attention from a > performance perspective. > > I have created a new test that also turns off writing of the stats file. > This will not pass regression tests, but it will show the stats write > overhead. will try to run those too in a few. Stefan ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
