Re: accessing primary key slower than accessing non primary key???

HK <harikrishnan@midascomm.com> writes:
>           time in ms per query retrieval
>         py key   non py key
>         ------   -----------
> 2000            15.8     15.7
> 10000           71.2     70.7
> 25000           174      173.5
> 100000          4319     3417

> As u see the non primary key retrieval is faster. AFAIK accessing primary
> key should be faster. Can anybody throw light on why is this anamoly.

There's nothing magic about primary keys in Postgres; I'd expect the
results to come out the same.

The first three of these look like they're indeed the same, to within
measurement error.  Not sure about the last one; perhaps you had some
effect of physical order in the table agreeing with the ordering of the
non-primary key?

            regards, tom lane