When in doubt - test.
Why not remove index in MySQL (or create index in PostgreSQL) and see
what happens.
Why trying compare "apples and oranges"?
Igor Neyman
> -----Original Message-----
> From: Yang Zhang [mailto:yanghatespam@gmail.com]
> Sent: Monday, February 22, 2010 1:37 PM
> To: Richard Broersma
> Cc: Frank Heikens; pgsql-general@postgresql.org
> Subject: Re: Sorting performance vs. MySQL
>
> On Mon, Feb 22, 2010 at 1:30 PM, Richard Broersma
> <richard.broersma@gmail.com> wrote:
> > On Mon, Feb 22, 2010 at 10:17 AM, Frank Heikens
> <frankheikens@mac.com> wrote:
> >
> >> There is no index on the column transactionid in your
> >> PostgreSQL-table, as there is in your MySQL-table. This
> explains the difference.
> >>
> >> CREATE INDEX i_transactionid ON public.metarelcloud_transactionlog
> >> (transactionid);
> >
> > Does an index help a sort operation in PostgreSQL?
>
> I also share the same doubt. An external merge-sort needs to
> make complete passes over the entire dataset, with no
> index-directed accesses.
> --
> Yang Zhang
> http://www.mit.edu/~y_z/
>