[ http://issues.apache.org/jira/browse/DERBY-539?page=all ]
Jean T. Anderson resolved DERBY-539:
------------------------------------
Fix Version: 10.2.0.0
Resolution: Fixed
Assign To: Jeff Levitt
Patch derby539-take2.diff committed, revision 386197. Modified file:
$ svn commit
Sending trunk/src/ref/rrefsqlj20937.dita
> Update the Create Index statement in the Derby documentation with additional
> information
> ----------------------------------------------------------------------------------------
>
> Key: DERBY-539
> URL: http://issues.apache.org/jira/browse/DERBY-539
> Project: Derby
> Type: Improvement
> Components: Documentation
> Reporter: Susan Cline
> Assignee: Jeff Levitt
> Priority: Minor
> Fix For: 10.2.0.0
> Attachments: derby539-take2.diff, derby539.diff, rrefsqlj20937.html
>
> In the 'Create Index' statement documentation of the 10.1 Reference Guide
> (derby/docs/10.1/ref/rrefsqlj20937.html)
> this statement is made about creating indexes and constraints:
> Indexes and constraints
> Unique, primary key, and foreign key constraints generate indexes that
> enforce or "back" the constraint (and are thus sometimes called backing
> indexes). If a column or set of columns has a UNIQUE or PRIMARY KEY
> constraint on it, you can not create an index on those columns. Derby has
> already created it for you with a system-generated name.
> This is true, but I think it can be expanded upon to be clearer. A
> suggestion for this is below:
> Indexes and constraints
> Unique, primary key, and foreign key constraints generate indexes that
> enforce or "back" the constraint (and are thus sometimes called backing
> indexes).
> If a column or set of columns has a PRIMARY KEY constraint on it, you can not
> create an index on those columns. If a column or set of columns has a UNIQUE
> constraint on it, you can not create an index on those columns, but you can
> create
> a PRIMARY KEY constraint on it. Addtionally, if this is the case, a backing
> index
> will be created for the PRIMARY KEY constraint so two indexes will now exist
> on the column or set of columns that had the UNIQUE constraint on it.
> This issue came up when I noticed that I could create a unique index on a
> column, then create a PK on that column. When I used a tool to generate DDL
> for the table I noticed one constraint and two indexes on the column which
> didn't make sense at first when reading the existing documentation. With the
> additional information above I think it explains the real behaviour better.
--
This message is automatically generated by JIRA.
-
If you think it was sent incorrectly contact one of the administrators:
http://issues.apache.org/jira/secure/Administrators.jspa
-
For more information on JIRA, see:
http://www.atlassian.com/software/jira
