Re: INDEX_MAX_KEYS to 64? - Mailing list pgsql-hackers

Rod Taylor wrote:
> On Tue, 2003-07-01 at 01:25, Tom Lane wrote:
>>Not without evidence that it doesn't cause performance penalties.
>>ISTM we have been through this discussion recently, and concluded
>>that 32 was the place to set it.
> 
> Yes, I was digging through that discussion.  The test used shows a 4%
> difference between 32 and 64.
> 
> do 100 times
>    select 2+2+2+2+2+2+ ... iterated 9901 times

There was also this, on disk usage - about 25% penalty going from 32 to 
64 (at least for small databases).

Joe Conway wrote:> Tom Lane wrote:>> Did you happen to make any notes about the disk space occupied by the>> database?
Onething I was worried about was the bloat that'd occur>> in pg_proc, pg_index, and pg_proc_proname_args_nsp_index.
Asidefrom>> costing disk space, this would indirectly slow things down due to>> more I/O to read these tables --- an
effectthat probably your test>> couldn't measure, since it wasn't touching very many entries in any>> of those
tables.>>>#define INDEX_MAX_KEYS        16> #define FUNC_MAX_ARGS        INDEX_MAX_KEYS> du -h --max-depth=1
/opt/data/pgsql/data/base/>2.7M    /opt/data/pgsql/data/base/1> 2.7M    /opt/data/pgsql/data/base/16862> 2.7M
/opt/data/pgsql/data/base/16863>2.7M    /opt/data/pgsql/data/base/16864> 3.2M    /opt/data/pgsql/data/base/16865> 2.7M
 /opt/data/pgsql/data/base/16866> 17M     /opt/data/pgsql/data/base>> #define INDEX_MAX_KEYS        32> #define
FUNC_MAX_ARGS       INDEX_MAX_KEYS>  du -h --max-depth=1 /opt/data/pgsql/data/base/> 3.1M
/opt/data/pgsql/data/base/1>3.1M    /opt/data/pgsql/data/base/16862> 3.1M    /opt/data/pgsql/data/base/16863> 3.1M
/opt/data/pgsql/data/base/16864>3.6M    /opt/data/pgsql/data/base/16865> 3.1M    /opt/data/pgsql/data/base/16866> 19M
 /opt/data/pgsql/data/base>> #define INDEX_MAX_KEYS        64> #define FUNC_MAX_ARGS        INDEX_MAX_KEYS> du -h
--max-depth=1/opt/data/pgsql/data/base/> 3.9M    /opt/data/pgsql/data/base/1> 3.9M    /opt/data/pgsql/data/base/16862>
3.9M   /opt/data/pgsql/data/base/16863> 3.9M    /opt/data/pgsql/data/base/16864> 4.4M
/opt/data/pgsql/data/base/16865>3.9M    /opt/data/pgsql/data/base/16866> 24M     /opt/data/pgsql/data/base>> #define
INDEX_MAX_KEYS       128> #define FUNC_MAX_ARGS        INDEX_MAX_KEYS> du -h --max-depth=1 /opt/data/pgsql/data/base/>
5.7M   /opt/data/pgsql/data/base/1> 5.7M    /opt/data/pgsql/data/base/16862> 5.7M    /opt/data/pgsql/data/base/16863>
5.7M   /opt/data/pgsql/data/base/16864> 6.3M    /opt/data/pgsql/data/base/16865> 5.7M
/opt/data/pgsql/data/base/16866>35M     /opt/data/pgsql/data/base>
 

Here's the thread:
http://archives.postgresql.org/pgsql-hackers/2002-08/msg00258.php

Joe


Joe