Re: help with query

>From what I can figure, queries like this run much quicker on other
databases, is this something that can be improved ?

Dave
On Thu, 2004-08-19 at 09:38, Brad Bulger wrote:
> You're doing a join except not, is the trouble, looks like. The query is really
> "FROM Tickets main, Links", but when Tickets.id is 17417, you've got no join
> to the Links table. So you end up getting every row in Links for each row in
> Tickets with id = 17417.
>
> I'd think this wants to be two queries or a union:
>
> SELECT distinct main.oid,main.* FROM Tickets main
> WHERE (main.EffectiveId = main.id)
> AND (main.Status != 'deleted')
> AND ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> AND ( (main.Queue = '9') )
> AND ( (main.id = '17417'))
> union
> SELECT distinct main.oid,main.* FROM Tickets main, Links
> WHERE (main.EffectiveId = main.id)
> AND (main.Status != 'deleted')
> AND ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> AND ( (main.Queue = '9') )
> AND ( (Links.Type = 'MemberOf') )
> AND ( (Links.LocalTarget = '17417') )
> AND ( (main.id = Links.LocalBase) ) OR (main.id = Links.LocalTarget) )
> ;
>
> or else, yah, a subquery:
>
> [...]
> AND (
> main.id = '17417'
> or
> exists(
> select true from Links
> where Type = 'MemberOf' and LocalTarget = '17417'
> and (LocalBase = main.id or LocalTarget = main.id)
> )
> )
>
> Those are the only things I can think of to make it work, anyways.
>
> Dave Cramer wrote:
>
> > RT uses a query like:
> >
> > SELECT distinct main.oid,main.* FROM Tickets main
> > WHERE
> > (main.EffectiveId = main.id)
> > AND
> > (main.Status != 'deleted')
> > AND
> > ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> > AND
> > ( (main.Queue = '9') )
> > AND ((
> > ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
> > OR
> > ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
> > or
> > (main.id = '17417')
> > )
> > );
> >
> >
> > which produces a query plan:
> >
> > Nested Loop (cost=0.00..813.88 rows=1 width=169)
> > Join Filter: (((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id
> > = 17417)) AND (("outer".id = "inner".localtarget) OR (("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("inner"
> > .localtarget = 17417) OR ("outer".id = 17417)) AND (("inner".localbase = 17417) OR ("inner".localtarget = 17417) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR (
> > "inner".localtarget = 17417) OR ("outer".id = 17417)) AND ((("inner"."type")::text = 'MemberOf'::text) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("inner".loca
> > lbase = 17417) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)) AND (("outer".id = "inner".localtarget) OR ("outer".id = "inner".localbase) OR ("outer".id = 17417)))
> > -> Index Scan using tickets1 on tickets main (cost=0.00..657.61 rows=1 width=169)
> > Index Cond: (queue = 9)
> > Filter: ((effectiveid = id) AND ((status)::text <> 'deleted'::text) AND ((("type")::text = 'ticket'::text) OR (("type")::text = 'subticket'::text)))
> > -> Seq Scan on links (cost=0.00..46.62 rows=1462 width=20)
> >
> > If I rewrite the query as:
> >
> > SELECT main.* FROM Tickets main
> > WHERE
> > (main.EffectiveId = main.id)
> > AND
> > (main.Status != 'deleted')
> > AND
> > ( (main.Type = 'ticket') OR (main.Type = 'subticket') )
> > AND
> > ( (main.Queue = '9') )
> > AND (
> > 17417 in (select links.localtarget from links where links.type='MemberOf' and main.id=links.localbase)
> > or
> > 17417 in ( select links.localbase from links where links.type='MemberOf' and main.id=links.localtarget)
> > or
> > main.id = '17417'
> > )
> > ;
> >
> > The time for the query goes from 1500ms to 15ms. The two OR clauses
> >
> > ( (Links.Type = 'MemberOf') AND (Links.LocalTarget = '17417') AND (main.id = Links.LocalBase) )
> > OR
> > ( (Links.Type = 'MemberOf') AND (Links.LocalBase = '17417') AND (main.id = Links.LocalTarget) )
> >
> > don't contribute to the result set in this particular dataset, which is why the speed increases so dramatically.
> >
> > Is there a way to rewrite the top query to get the same results? I have already talked to Best Practical,
> > and subqueries are not easily embraced.
> >
> > Dave
>
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--
Dave Cramer
519 939 0336
ICQ # 14675561