Horton

Thread

  1. Re: [HACKERS] Execution time.

    Shiby Thomas <sthomas@cise.ufl.edu> — 1998-02-04T18:07:01Z

    => > Is the size of the hash bucket dependent on the number of buffers available ?
=> > If so, with -B 30000, it might create huge hash buckets and hence the
=> > hash join could degenerate to a nested loops join. Is that possible -- just
=> > checking. What could be good values for -B and -S. The largest table I am
=> > joining is about 60M
=> 
=> 	My production server runs with a -B 256, and a -S 10240
=> 
=> 
With less buffers, it is giving "hash table out of memory" error.
I ran with -B 512

AGG :c=435416.5312 :s=0 :w=0 
   l: GROUP :c=435416.5312 :s=0 :w=0 
      l: SORT :c=435416.5312 :s=0 :w=0 
         l: HASHJOIN :c=435416.5312 :s=305715 :w=16 
            l: SEQSCAN :c=36107.7500 :s=917144 :w=8  ( t1 )
            r: HASH :c=0.0000 :s=0 :w=0 
               l: SEQSCAN :c=36107.7500 :s=917144 :w=8  ( t1 )
ERROR:  hash table out of memory. Use -B parameter to increase buffers.

  2. Re: [HACKERS] Execution time.

    Vadim B. Mikheev <vadim@sable.krasnoyarsk.su> — 1998-02-05T01:51:25Z

    Shiby Thomas wrote:
> 
> => > Is the size of the hash bucket dependent on the number of buffers available ?
> => > If so, with -B 30000, it might create huge hash buckets and hence the
> => > hash join could degenerate to a nested loops join. Is that possible -- just
> => > checking. What could be good values for -B and -S. The largest table I am
> => > joining is about 60M
> =>
> =>      My production server runs with a -B 256, and a -S 10240
> =>
> =>
> With less buffers, it is giving "hash table out of memory" error.

Known bug...

> I ran with -B 512
> 
> AGG :c=435416.5312 :s=0 :w=0
>    l: GROUP :c=435416.5312 :s=0 :w=0
>       l: SORT :c=435416.5312 :s=0 :w=0
>          l: HASHJOIN :c=435416.5312 :s=305715 :w=16
>             l: SEQSCAN :c=36107.7500 :s=917144 :w=8  ( t1 )
>             r: HASH :c=0.0000 :s=0 :w=0
>                l: SEQSCAN :c=36107.7500 :s=917144 :w=8  ( t1 )
> ERROR:  hash table out of memory. Use -B parameter to increase buffers.

Try to create indices...

Vadim