MySQL Bugs: #13375: Index with Desc sort feature

Bug #13375	Index with Desc sort feature
Submitted:	21 Sep 2005 11:14	Modified:	20 Dec 2006 5:39
Reporter:	Sebastián Araya	Email Updates:
Status:	Verified	Impact on me:	None
Category:	MySQL Server: DDL	Severity:	S4 (Feature request)
Version:	4.x, 5.x, 6.0	OS:	Any (All)
Assigned to:	Geir Høydalsvik	CPU Architecture:	Any

Description:
  In case you need to sort in descending way, you need to build a new field which can be used to perform the index creation, because MySQL only index ascending collation.

How to repeat:
  As section 13.1.4 says: an index_col_name specification can end with ASC or DESC. These keywords are allowed for future extensions for specifying ascending or descending index value storage. Currently they are parsed but ignored; index values are always stored in ascending order. 

Suggested fix:
  Index in ascending and descending order.

Thank you for a reasonable feature request.

Supporting DESC index keys is a feature request.
Changing MySQL to not parse and ignore unsupported features is a bug fix.

http://dev.mysql.com/doc/refman/5.0/en/create-index.html

'parsed but ignored' is a bad idea

bug #61060 is a duplicate of this

This is standard in Postgres, SQL Server, Oracle, Sybase etc etc etc. Can we please see this implemented in MySQL?

Its in the documentation for create index syntax with the comment  

"These keywords are permitted for future extensions for specifying ascending or descending index value storage. Currently, they are parsed but ignored; index values are always stored in ascending order."

Its retarded and very wasteful to make extra columns with negated values so we can make an order by "asc desc asc" into "desc desc desc" for example....

Pretty please?

Hi
I echo all the above comments. Having the ability to create an index DESC is really a fundamental requirement and this feature should be high up on the list for implementation.

Regards

Dave Edwards

Please please please implement this.

I would definitely argue that this is actually two tickets: a a feature request, and a bug.

People would expect that as the syntax is supported at the time of index creation, the index will be properly created.

What happens if you create an index with DESC? The index gets created as ASC? This is not creating what I have requested, so is a bug.

Were the DDL to fail so that you cannot create DESC indexes, adding in support for DESC indexes would be a feature request, don't you think?

So the bug is: DESC indexes created as ASC
So the enhancement is: DESC index support

Further, the MySQL workbench allows you to edit indexes so they are ASC or DESC - should this feature be removed from the workbench?

Having it accept it silently makes it seem that you have this functionality :)

Matthew, the list of silently ignored syntax is the topic of bug #47771 :)

Thanks Shane :) Madness....

And the number one search result for "parsed but ignored" on Google:
http://www.google.com/search?gcx=c&ix=c2&sourceid=chrome&ie=UTF-8&q=parsed+but+ignored

is dedicated to this issue:
http://mysqlha.blogspot.com/2009/01/parsed-but-ignored.html

Goodness gracious, this should be top priority. MySql looks like a children's toy without this feature.

Agree with all. Very needed feature...

+1

This bug is fixed in the 8.0 optimizer labs release: http://mysqlserverteam.com/mysql-8-0-labs-descending-indexes-in-mysql/