Re: Compression and on-disk sorting

On Wed, May 17, 2006 at 10:06:04AM +0200, Martijn van Oosterhout wrote:
> On Wed, May 17, 2006 at 09:45:35AM +0200, Albe Laurenz wrote:
> > Oracle's compression seems to work as follows:
> > - At the beginning of each data block, there is a 'lookup table'
> > containing frequently used values in table entries (of that block).
> > - This lookup table is referenced from within the block.
>
> Clever idea, pity we can't use it (what's the bet it's patented?). I'd
> wager anything beyond simple compression is patented by someone.
>
> The biggest issue is really that once postgres reads a block from disk
> and uncompresses it, this block will be much larger than 8K. Somehow
> you have to arrange storage for this.

It's entirely possible that the best performance would be found from not
un-compressing blocks when putting them into shared_buffers, though.
That would mean you'd "only" have to deal with compression when pulling
individual tuples. Simple, right? :)
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Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
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