Re: updates (postgreSQL) very slow
От | Bobbie van der Westhuizen |
---|---|
Тема | Re: updates (postgreSQL) very slow |
Дата | |
Msg-id | 40502E89.22929.1E4AF8B6@localhost обсуждение исходный текст |
Ответ на | Re: updates (postgreSQL) very slow (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: updates (postgreSQL) very slow
Re: updates (postgreSQL) very slow |
Список | pgsql-general |
On 11 Mar 2004 at 2:01, Tom Lane wrote: Fred Moyer <fred@redhotpenguin.com> 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. ________________________________________________________ __ Bobbie van der Westhuizen Quantitative Animal Breeding (BLUP) ARC - Animal Improvement Institute +27-12-672-9128 (o/h) +27-12-665-1419 (fax) bobbie@irene.agric.za ________________________________________________________ __
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