Re: experiments in query optimization

On Thu, Apr 1, 2010 at 2:15 PM, Faheem Mitha <faheem(at)email(dot)unc(dot)edu> wrote:
> I had set the foreign keys in question (on the geno table) to be primary
> keys. This is because this setup is basically a glorified spreadsheet, and I
> don't want more than one cell corresponding to a particular tuple of
> idlink.id and anno.id (the conceptual rows and cols). Since a primary key
> defines an index, I thought putting indexes on idlink_id and anno_id was
> redundant. However, it looks like (unsurprisingly) the index corresponding
> to the primary key is across both columns, which may not be what is wanted
> for the aforesaid join

Actually it is what is wanted - that is good.

> So, should I add indexes on the individual foreign key cols idlink_id
> and anno_id after all?

I doubt that would help.

The bottom line may be that you're dealing with hundreds of millions
of rows here, so things are going to take a long time. Of course you
can always get more/faster memory, a bigger I/O subsystem, faster
processors... and it could be that with detailed study there are
optimizations that could be done even without spending money, but I
think I'm about tapped out on what I can do over an Internet mailing
list.

...Robert