Re: selecting random rows

Dennis Gearon wrote:
> If you have a nice small Primary key on the table, you can so something
> like this:
>
> SELECT field_list
> FROM table
> WHERE primary_key IN(
>     SELECT primary_key,
>     FROM table
>     ORDER by RANDOM()
>     LIMIT your_limit);
>
> This may not be the exact sequence, and there is some workarounds for
> some slowness in the IN() keyword. Others may comment at will, and
> polish this up?
>
What exactly does that do for me?  Postgres still has to go over the whole table to get
the primary keys.