Re: Inefficient query plan

On Mon, Aug 23, 2010 at 4:15 AM, Jann Röder <roederja@ethz.ch> wrote:
> Am 23.08.10 07:52, schrieb Scott Marlowe:
>> Also are a.indexid and b.indexid the same type?
>>
>
> You mean ItemID? Fields of the same name are of the same type - so yes.
> According to the documentation pgsql adds indexes for primary keys
> automatically so (b.itemID, b.indexNumber) is indexed. Or do you think
> adding an extra idnex for b.itemID alone will help? If I understand the
> documentation correctly, pqSQL can use the first column of a
> multi-column index as if it was indexed individually... but maybe I'm
> wrong here.

It can but that doesn't mean it will.  A multi-column index is often
quite a bit bigger than a single column one.

What happens if you try

set enable_seqscan=off;
(your query here)