On 10/13/2010 3:19 AM, Mark Kirkwood wrote:
I think that major effect you are seeing here is that the UPDATE has
made the table twice as big on disk (even after VACUUM etc), and it has
gone from fitting in ram to not fitting in ram - so cannot be
effectively cached anymore.
In the real world, tables are larger than the available memory. I have
tables of several hundred gigabytes in size. Tables shouldn't be
"effectively cached", the next step would be to measure "buffer cache
hit ratio", tables should be effectively used.
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Mladen Gogala
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