[Monetdb-developers] Monetdb-developers Digest, Vol 30, Issue 10

Martin Kersten Martin.Kersten at cwi.nl
Sun Nov 23 18:15:49 CET 2008


Peter Boncz wrote:
> Hi Stefan (the non-german .de one)
>   
> session.
>
> I also recall that in case of the Skyserver TB dataset, key checking was
> disabled to to similar problems.
>   
No. The key checking was initially turned off, because the hash table 
(32-bit) could not
well cope with the 13.000.000.000 tuples in the table, causing lengthly 
hash collisions chains.
It took a day....to handle the request.
Work is in progress to speed this up using a straightforward clustering 
on the built-in
hash. The preliminary code has been checked in.
>
> PS
> The likely cause for the problem is a shortage of swap space. Increasing
> your swap file size (with a few 10s of GB) should be a workaround for the
> problem.
>   
The swap space set aside for Skyserver was 128G
>
>
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