* Nis Jørgensen <[EMAIL PROTECTED]> [20070730 18:33]:
> It seems to me the subselect plan would benefit quite a bit from not
> returning all rows, but only the 10 latest for each user. I believe the
> problem is similar to what is discussed for UNIONs here:
>
> http://groups.google.dk/group/pgsql.
* Craig James <[EMAIL PROTECTED]> [20070728 22:00]:
> >>SELECT * FROM (
> >> (SELECT * FROM large_table lt
> >> WHERE lt.user_id = 12345
> >> ORDER BY created_at DESC LIMIT 10) AS q1
> >> UNION
> >> (SELECT * FROM large_table lt
> >> WHERE user_id IN (SELECT contact_id FROM relationships WHERE
> >
* [EMAIL PROTECTED] <[EMAIL PROTECTED]> [20070728 21:05]:
> Let's try putting the sort/limit in each piece of the UNION to speed them up
> separately.
>
> SELECT * FROM (
> (SELECT * FROM large_table lt
> WHERE lt.user_id = 12345
> ORDER BY created_at DESC LIMIT 10) AS q1
> UNION
> (SELECT *
* Nis Jørgensen <[EMAIL PROTECTED]> [20070727 20:31]:
> How does the "obvious" UNION query do - ie:
>
> SELECT * FROM (
> SELECT * FROM large_table lt
> WHERE lt.user_id = 12345
>
> UNION
>
> SELECT * FROM large_table lt
> WHERE user_id IN (SELECT contact_id FROM relationships WHERE user_id=1234
Dear list,
I am having problems selecting the 10 most recent rows from a large
table (4.5M rows), sorted by a date column of that table. The large
table has a column user_id which either should match a given user_id,
or should match the column contact_id in a correlated table where the
user_id of
