Re: Changes improve the performance of INSERT and UPDATE

Tom Lane wrote:
> I've been testing this patch a bit, and I'm unable to measure any
> consistent improvement in pgbench times (sometimes it seems to win,
> and some other times it doesn't).  And gprof still swears up and down
> that PageAddItem is only about 0.1% of the runtime, which would make
> it impossible to obtain more than an 0.1% speedup.  I'm inclined to
> write off your result as measurement error --- it's notoriously hard
> to get reproducible results out of pgbench.
  OK.  I think that your environment is more realistic than mine.  I 
have been convinced to your result.  Surely, my patch may not be allround.

> I tried making a million-row table with just two int4 columns and then
> duplicating it with CREATE TABLE AS SELECT.  In this context gprof
> shows PageAddItem as taking 7% of the runtime, which your patch knocks
> down to 1.5%.  This seems to be about the best possible real-world case,
> though (the wider the rows, the fewer times PageAddItem can loop), and
> so I'm still unconvinced that there's a generic gain here.
  In fact, I have created this patch since I wants to make COPY FROM 
faster.  So, it is not rare case for me.  There may be no generic gain 
here, but I think it is very important to make COPY FROM and so on more 
speedy.  Of course, if we can prevent the increase in a page header, 
it's better.

> PS: If we were going to apply the patch, I'd be inclined to compensate
> for the space usage by removing the pd_tli field, which isn't actually
> ever used anywhere in the current code.
  It is very a good idea if it's possible.  I want you to surely think 
positively very much.

-- 
Hiroki Kataoka <kataoka@interwiz.jp>