RE: range-bound queries

From: Bobak, Mark <>
Date: Mon, 27 Jul 2009 17:17:36 -0400
Message-ID: <>

Hi Jonathan,

Are wrong results possible? I agree that it's possible that Oracle may not do what's intended, and that could cause a big performance problem, but I don't think it will ever return wrong results, will it?

I agree, the solution you point out in the comment is a good idea. I'm just saying that the way Dan has it written, though poor performance could result, I don't think a wrong result is possible.

In my case, since the code has been in production for 4+ years, I'm probably not going to change it, unless we actually run into a problem.....


-----Original Message-----
From: [] On Behalf Of Jonathan Lewis Sent: Monday, July 27, 2009 4:49 PM
Subject: Re: range-bound queries

I think the problem with the code is that it could return the wrong result as it depends on Oracle using a specific index in a specific way.

The code towards the end of the response addresses that issue, though, by including the extra subquery:   "where ip = (select min(ip) > :bind_ip)"

Even if something goes wrong and Oracle uses an undesirable access path it will still find the correct value.


Jonathan Lewis

Author: Cost Based Oracle: Fundamentals

The Co-operative Oracle Users' FAQ

  • Original Message ----- From: "Bobak, Mark" <> To: <>; "ORACLE-L" <> Sent: Monday, July 27, 2009 9:42 PM Subject: RE: range-bound queries

> Hi Andrew,
> The article is all Dan Tow. I can’t take credit for any authorship. It all
> started w/ a question I asked here, on Oracle-L, which Dan answered. He got
> the idea for the article, and asked if he could use my name and SQL as is, or
> if I wanted him to obfuscate. I told him to go ahead. But, the authorship is
> all him.
> As to the rownum=1, the whole idea there is to short circuit the range scan,
> as soon as you have a single match. It’s a way of implementing the idea
> behind the “least-greater-than-or-equal-to” and
> “greatest-less-than-or-equal-to” operators which he discusses in the article.
> To answer your questions, the code that Dan provided went into production
> shortly after he provided me that solution, and I believe it’s still going
> strong, 4 years later. Can you expand on your concerns about it being “safe”?
> To my knowledge, there’s nothing inherently dangerous about it.
> -Mark
> From: [] On
> Behalf Of Andrew Kerber
> Sent: Monday, July 27, 2009 4:30 PM
> Subject: range-bound queries
> I saw an article recently (the article is actually dated 2005), by Dan Tow and
> Mark Bobak showing a method of speeding up range bound queries by qualifying
> on rownum=1 as part of the query.
> Has anyone been able to successfully do that with production SQL?
> If so, are there any special conditions that make this technique safe?
> Has anyone found another way to reproduce this effect?
> --
> Andrew W. Kerber


i0zX+n{+i^ Received on Mon Jul 27 2009 - 16:17:36 CDT

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