On 20 Jan 2005 at 6:14, Stephan Szabo wrote:
> On Wed, 19 Jan 2005, Dan Langille wrote:
> > Hi folks,
> > Running on 7.4.2, recently vacuum analysed the three tables in
> > question.
> > The query plan in question changes dramatically when a WHERE clause
> > changes from ports.broken to ports.deprecated. I don't see why.
> > Well, I do see why: a sequential scan of a 130,000 rows. The query
> > goes from 13ms to 1100ms because the of this. The full plans are at
> > http://rafb.net/paste/results/v8ccvQ54.html
> > I have tried some tuning by:
> > set effective_cache_size to 4000, was 1000
> > set random_page_cost to 1, was 4
> > The resulting plan changes, but no speed improvment, are at
> > http://rafb.net/paste/results/rV8khJ18.html
> > Any suggestions please?
> As a question, what does it do if enable_hashjoin is false? I'm wondering
> if it'll pick a nested loop for that step for the element/ports join and
> what it estimates the cost to be.
With enable_hashjoin = false, no speed improvement. Execution plan
Dan Langille : http://www.langille.org/
BSDCan - The Technical BSD Conference - http://www.bsdcan.org/
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match