On Mon, Feb 11, 2008 at 03:33:37PM -0600, Scott Marlowe wrote:
> On Feb 11, 2008 2:03 PM, salman <salmanb@xxxxxxxxxxxxxxxxxxxx> wrote:
> > I'm planning to cluster a few large tables in our database but I'm
> > unable to find any recommendations/documentation on best practices --
> > Mainly, whether it's better to use an index which has a higher idx_scan
> > value, a higher idx_tup_read value, or the higest idx_tup_fetch value.
> >
> > I'm assuming that idx_tup_read would probably be the best choice, but
> > want to get other opinions before proceeding.
>
> If you've got two indexes that are both being hit a lot, it might be
> worth looking into their correlation, and if they get used a lot
> together, look at creating an index on both.
>
> But I'd guess that idx_tup_read would be a good bet.
You might also consider the ratio idx_tup_read::float8 / idx_scan
to see which indexes access a lot of rows per scan.
--
Michael Fuhr
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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
match
