Re: Reduce WAL logging of INSERT SELECT

On Thu, Aug 4, 2011 at 10:46 PM, Bruce Momjian <bruce@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.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
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