On Thu, Aug 4, 2011 at 11:07 PM, Bruce Momjian <br...@momjian.us> wrote: > Simon Riggs wrote: >> On Thu, Aug 4, 2011 at 10:46 PM, Bruce Momjian <br...@momjian.us> wrote: >> >> > Right. ?I brought up SELECT INTO because you could make the argument >> > that INSERT ... SELECT is not a utility command like the other ones and >> > therefore can't be done easily, but CREATE TABLE AS is internal SELECT >> > INTO and implemented in execMain.c, which I think is where INSERT ... >> > SELECT would also be implemented. >> >> What you should be asking is whether the optimisation would be >> effective for INSERT SELECT, or even test it. >> >> My observation is that the optimisation is only effective for very >> large loads that cause I/O. As RAM sizes get bigger, I'm inclined to >> remove the optimisation and make it optional since it is ineffective >> in many cases and negative benefit for smaller cases. > > I am confused how generating WAL traffic that is larger than the heap > file we are fsync'ing can possibly be slower.
I'm telling you what I know to be true as an assistance to you. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
