2007/10/9, Martijn van Oosterhout <[EMAIL PROTECTED]>:
> On Tue, Oct 09, 2007 at 06:40:23PM +0200, Pavel Stehule wrote:
> > It needs always seq scan :(, and take space on buffer cache. Solution
> > based on random generated PK are much faster. I collaborate with one
> > my customer. He shows random products from 10K products on every page
> > of one eShop. And he cannot understand, so ORDER random() LIMIT is bad
> > trick, because this trick is on PostgreSQL FAQ.
> It's the only trick that works in all situations though. There are
> ofcourse faster methods, but they require information about the
> distribution of the values, the type, PKs, indexes etc...
> The standard does have stuff relating to extracting samples from
> tables, but they're not implemented.

I agree. I don't wont to remove it from FAQ. I would to add note, so
sometimes is necessary to find other trick.


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TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not

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