Re: updates (postgreSQL) very slow

On 11 Mar 2004 at 2:01, Tom Lane wrote:

Fred Moyer  writes:
> On Wed, 2004-03-10 at 15:30, Tom Lane wrote:
>> A while, sure, but 2 hours seems excessive to me too.

> If there are no foreign keys or triggers and updating each row is taking
> one drive seek ( approximately 9 ms with the 80 gig IDE drive being used
> here ) then to do 747524 seeks will take 6727716 ms, about 10% less than
> the time of 7628686 ms for the update above.  Is this is an accurate
> estimate or are these numbers just coincidence?

Probably coincidence.  There's no reason to think that a large UPDATE
would expend one disk seek per updated row on average --- there's 
enough
buffering between the UPDATE and the drive heads that under normal
circumstances the cost should be lots less.

If I had to bet at this point I'd bet on inefficient foreign-key checks,
but since we haven't seen any schema details that's purely 
speculation.

			regards, tom lane

There are no foreign-keys in this table.  What schema details do you 
need, then I can give it to you. I am a new user of postgreSQL so I am 
not clude-up with all of the stuff.
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Bobbie van der Westhuizen
Quantitative Animal Breeding (BLUP)
ARC - Animal Improvement Institute
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bobbie@irene.agric.za
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