Re: trouble with (lack of) indexing

On Thu, May 09, 2002 at 07:38:06PM -0400, Tom Lane wrote:
> =?iso-8859-1?Q?S=F8ren?= Boll Overgaard <postgres(at)fork(dot)dk> writes:
> > explain SELECT ht.id,hq.ip,hq.id FROM
> > hostsqueue as hq,hoststests as ht WHERE ht.hostsqueue_id=hq.id;
> > NOTICE: QUERY PLAN:
>
> > Hash Join (cost=776.05..2904.36 rows=84 width=24)
> > -> Seq Scan on hoststests ht (cost=0.00..2126.84 rows=84 width=8)
> > -> Hash (cost=776.04..776.04 rows=4 width=16)
> > -> Seq Scan on hostsqueue hq (cost=0.00..776.04 rows=4 width=16)
>
>
> If there's only 84 rows it's hardly going to matter which plan we choose
> ;-). Please show us the results from the production database, not the
> toy-sized tables.

Sorry, my bad.
Here is the real stuff:

explain SELECT ht.id,hq.ip,hq.id FROM hostsqueue as hq,hoststests as ht WHERE ht.hostsqueue_id=hq.id;
NOTICE: QUERY PLAN:

Hash Join (cost=75331.89..127823.94 rows=160293 width=24)
-> Seq Scan on hoststests ht (cost=0.00..49686.93 rows=160293 width=8)
-> Hash (cost=75243.51..75243.51 rows=35351 width=16)
-> Seq Scan on hostsqueue hq (cost=0.00..75243.51 rows=35351 width=16)

EXPLAIN

>
> If you have 7.2 then EXPLAIN ANALYZE is much more useful to show than
> plain EXPLAIN. Also, you could try doing "SET enable_seqscan = off"
> and see how the plan changes.

After changing the enable_seqscan, the plan looks like this:

explain SELECT ht.id,hq.ip,hq.id FROM hostsqueue as hq,hoststests as ht WHERE ht.hostsqueue_id=hq.id;
NOTICE: QUERY PLAN:

Merge Join (cost=0.00..772324.63 rows=160293 width=24)
-> Index Scan using hostsqueue_pkey on hostsqueue hq (cost=0.00..137603.50 rows=35351 width=16)
-> Index Scan using idx_htsts_hq on hoststests ht (cost=0.00..632228.35 rows=160293 width=8)

EXPLAIN

As far as I can tell, that is excactly what we want. I will let the guys who
usually mess with the database have a go at it.

Thanks for the input so far, I really appreciate it.

--
Søren O. ,''`.
: :' :
public key: finger boll <at> db.debian.org `. `'
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