On Nov 20, 2011, at 20:50, Phoenix Kiula <phoenix.kiula@gmail.com> wrote:
> On Mon, Nov 21, 2011 at 7:26 AM, Gavin Flower
> <GavinFlower@archidevsys.co.nz> wrote:
>
>> How about having 2 indexes: one on each of ip & url_md5? Pg will combine the
>> indexes as required, or will just use one if that is best.
>
>
>
> Thanks Gavin. Question: what if I have a joined index? If from a
> joined index I only use the first column (say, "ip") will a joined
> index still be used?
>
> It is cleaner to create two indexes for the two columns. Which is recommended?
>
An index on (a, b) can be used for queries involving only a but not for those involving only b.
Neither is recommended - both have their benefits and limitations.
David J.
