List:Internals« Previous MessageNext Message »
From:Michael Widenius Date:January 26 2002 5:06pm
Subject:Re: Descending indexes not working?
View as plain text  

>>>>> "Jeremy" == Jeremy Zawodny <jzawodn@stripped> writes:

Jeremy> On Fri, Jan 18, 2002 at 12:40:00AM -0800, Simon Kirby wrote:
>> MySQL appears to be having problems walking backwards on the index when
>> starting from a known row.
>> On the web documentation, it looks like this is supposed to work:

Jeremy> [snip]

>> Does anybody have any ideas? :)  MySQL 3.23.46, by the way.

Jeremy> I think that the "walking backwards" optimizations were introduced
Jeremy> in the MySQL 4.0 tree.

That's correct. Simon, could you please download MySQL 4.0.1 and try
if this works better for you.

We shall also add the ORDER BY DESC on an index to the MySQL benchmark
suite to clearly show this difference between 3.23 and 4.0.

The things we need to tests are:

... WHERE key_prefix BETWEEN # and # ORDER BY key_prefix DESC

with one and two key parts.  We also need to execute the same queries
without DESC to get an comparison of this.

Descending indexes not working?Simon Kirby18 Jan
  • Re: Descending indexes not working?Jeremy Zawodny18 Jan
    • Re: Descending indexes not working?Michael Widenius26 Jan