> Can I try again? :)
>
> How hard would it be to teach the planner about preserving uniqueness of
> relations in subqueries?
> And using that information to remove unnecessary self joins on unique sets?
>
> I can try to rewrite some queries to test it on real data for how much
> gain it would prov
Tom Lane wrote:
> Rikard Pavelic writes:
>
>> It would be great if Postgres could rewrite this query
>>
>
> AFAICS those queries are not going to produce the same results,
> so Postgres would be 100% incorrect to rewrite it like that for you.
>
> (If they do produce the same results, it wo
Rikard Pavelic writes:
> It would be great if Postgres could rewrite this query
AFAICS those queries are not going to produce the same results,
so Postgres would be 100% incorrect to rewrite it like that for you.
(If they do produce the same results, it would depend on a bunch
of assumptions you
On Wed, 1 Apr 2009, Rikard Pavelic wrote:
It would be great if Postgres could rewrite this query
SELECT bt1.id, bt1.total, sq.id, sq.total
FROM
big_table bt1
INNER JOIN small_table st1 on st1.big_id = bt1.id
INNER JOIN
(
SELECT bt2.id, st2.total
How hard would it be to teach planer to optimize self join?
While this query which demonstrates it is not that common
SELECT count(*)
FROM
big_table a
INNER JOIN big_table b ON a.id = b.id;
This type of query (self joining large table) is very common
(at least in our environment
