Re: Slow duplicate deletes

On 5 March 2012 22:43, DrYSG <ygutfreund(at)draper(dot)com> wrote:
> One point I might not have made clear. The reason I want to remove duplicates
> is that the column "data_object.unique_id" became non-unique (someone added
> duplicate rows). So I added the bigSeriel (idx) to uniquely identify the
> rows, and I was using the SELECT MIN(idx) and GroupBy to pick just one of
> the rows that became duplicated.
>
> I am going to try out some of your excellent suggestions. I will report back
> on how they are working.
>
> One idea that was given to me was the following (what do you think Merlin?)
>
> CREATE TABLE portal.new_metatdata AS
> select distinct on (data_object.unique_id) * FROM portal.metadata;
>
> Or something of this ilk should be faster because it only need to do a
> sort on data_object.unique_id and then an insert. After you have
> verified the results you can do:
>
> BEGIN;
> ALTER TABLE portal.metatdata rename TO portal.new_metatdata_old;
> ALTER TABLE portal.new_metatdata rename TO portal.metatdata_old;
> COMMIT;

This sounds like a good way to go, but if you have foreign keys
pointing at portal.metadata I think you will need to drop and recreate
them again after the rename.

--
Michael Wood <esiotrot(at)gmail(dot)com>