Re: Any risk in increasing BLCKSZ to get larger tuples?

Steve Wolfe wrote:
>
> > > A trick you can use in 7.0.* to squeeze out a little more space is
> > > to declare your large text fields as "lztext" --- this invokes
> > > inline compression, which might get you a factor of 2 or so on typical
> > > mail messages.  lztext will go away again in 7.1, since TOAST supersedes
> > > it,
> >
> > Uh, why.  Does TOAST do automatic compression?  If people need to store
> > huge blocks of text (like a DNA sequence) inline compression isn't just
> > a hack to squeeze bigger text into a tuple.
>
>   I'd guess that it's a speed issue.  Decompressing everything in the table
> for every select sounds like a great waste of CPU power, to me, especially
> when hard drives and RAM are cheap.  Kind of like the idea of "drivespace"
> on Windows - nice idea, but it slowed things down quite a bit.

In some cases yes, in some no.  Simple text should compress/decompress
quickly and the cpu time wasted is made up for by less hardware access
time and smaller db files.  If you have a huge database the smaller db
files could be critical.


--
Joseph Shraibman
jks@selectacast.net
Increase signal to noise ratio.  http://www.targabot.com