Re: A fairly obvious optimization?

From: "Zeugswetter Andreas SB SD" <ZeugswetterA(at)spardat(dot)at>
To: "Dann Corbit" <DCorbit(at)connx(dot)com>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: A fairly obvious optimization?
Date: 2002-05-16 08:07:01
Message-ID: 46C15C39FEB2C44BA555E356FBCD6FA4961DCF@m0114.s-mxs.net
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers


> The select(min) and select(max) took as long as the table scan to find
> the count. It seems logical if a btree type index is available (such
> as pk_cnx_ds_sis_bill_detl_tb) where the most significant bit of the
> index is the column requested, it should be little more than a seek
> first or seek last in the btree. Obviously, it won't work with a hashed
> index (which is neither here nor there).

In the meantime you can use:
select extr_stu_id from cnx_ds_sis_bill_detl_tb order by 1 desc limit 1; -- max
select extr_stu_id from cnx_ds_sis_bill_detl_tb order by 1 asc limit 1; -- min

I guess that is the reason why nobody felt really motivated to implement
this optimization. Besides these statements are more powerful, since they can fetch
other columns from this min/max row. The down side is, that this syntax varies across
db vendors, but most (all?) have a corresponding feature nowadays.

select first 1
select top 1 ...

This is actually becoming a FAQ :-)

Andreas

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message D'Arcy J.M. Cain 2002-05-16 10:11:43 Money type
Previous Message Hannu Krosing 2002-05-16 06:21:40 Re: A fairly obvious optimization?