Re: DBT-3 with SF=20 got failed

Hello KaiGain-san,

On 08/19/2015 03:19 PM, Kohei KaiGai wrote:
> Unless we have no fail-safe mechanism when planner estimated too
> large number of tuples than actual needs, a strange estimation will
> consume massive amount of RAMs. It's a bad side effect.
> My previous patch didn't pay attention to the scenario, so needs to
> revise the patch.

I agree we need to put a few more safeguards there (e.g. make sure we 
don't overflow INT when counting the buckets, which may happen with the 
amounts of work_mem we'll see in the wild soon).

But I think we should not do any extensive changes to how we size the 
hashtable - that's not something we should do in a bugfix I think.

regards

--
Tomas Vondra                  http://www.2ndQuadrant.com
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