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From Brandon Williams <dri...@gmail.com>
Subject Re: Bad read performances: 'few rows of many columns' vs 'many rows of few columns'
Date Tue, 09 Mar 2010 20:49:07 GMT
On Tue, Mar 9, 2010 at 2:28 PM, Sylvain Lebresne <sylvain@yakaz.com> wrote:

> > A row causes a disk seek while columns are contiguous.  So if the row
> isn't
> > in the cache, you're being impaired by the seeks.  In general, fatter
> rows
> > should be more performant than skinny ones.
>
> Sure, I understand that. Still, I get 400 columns by seconds (ie, 400 seeks
> by
> seconds) when the rows only have one column by row, while I have 10 columns
> by seconds when the row have 100 columns, even though I read only the first
> column.
>

Doesn't that imply the disk is having to seek further for the rows with more
columns?

-Brandon

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