Horton

Re: [HACKERS] Execution time.

Vadim B. Mikheev <vadim@sable.krasnoyarsk.su>

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From: "Vadim B. Mikheev" <vadim@sable.krasnoyarsk.su>
To: Shiby Thomas <sthomas@cise.ufl.edu>
Cc: The Hermit Hacker <scrappy@hub.org>, pgsql-hackers@postgreSQL.org
Date: 1998-02-05T01:51:25Z
Lists: pgsql-hackers 
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