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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-789) Usability issue: "Constraints have the same set of columns"
Date Wed, 03 Mar 2010 10:20:27 GMT

    [ https://issues.apache.org/jira/browse/DERBY-789?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12840561#action_12840561
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Knut Anders Hatlen commented on DERBY-789:
------------------------------------------

I think the relevant section in SQL:2003 is 11.7 <unique constraint definition>.

It talks about both PRIMARY KEY and UNIQUE as uniqueness constraints. Further, syntax rule
3b says:

> The set of columns in the <unique column list> shall be distinct from the unique
columns of any other
> unique constraint descriptor that is included in the base table descriptor of T.

So it seems allowing PRIMARY KEY and UNIQUE on the same set of columns would be a non-standard
extension. It may still be useful, as it makes it easier to port applications to Derby, but
we cannot expect any advice from the standard as to what's the correct behaviour for DROP
CONSTRAINT on such constraints (I would argue, though, that the MySQL/PrimaryImpliesUnique.diff
behaviour is more intuitive than the PostgreSQL behaviour.)

> Usability issue: "Constraints have the  same  set of columns"
> -------------------------------------------------------------
>
>                 Key: DERBY-789
>                 URL: https://issues.apache.org/jira/browse/DERBY-789
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Øystein Grøvlen
>            Assignee: Bryan Pendleton
>            Priority: Minor
>         Attachments: PrimaryImpliesUnique.diff
>
>
> Legolas Woodland reported on derby-user that derby return errors like :
> org.apache.derby.client.am.SqlException:                    Constraints
> 'SQL060103004635123'  and 'SQL060103004635121'  have the  same  set of
> columns, which is not allowed.
> He got this when creating a table like this:
> create  table  WEBSITES (USERID  integer  not  null unique,  WEBSITEID
> bigint  not  null unique,  DOMAINNAME  varchar(255)  not null  unique,
> DESCRIPTION  varchar(255),  PPVIEW   double,  PPCLICK  double,  PPWEEK
> double, totalClick bigint,  totalView bigint, active smallint, primary
> key (WEBSITEID));
> Omitting the unique specifier made things work. 
> I think this is a usability issue.   At least, one should not present names to the user,
that has been generated internally.  Instead, it would be helpful if the names of the columns
involved was mentioned. I see two ways to solve this:
> 1. Return error that says that  duplicate contraints on the following columns are not
allowed.
> 2. Allow this and use same index for both constraints.  (I guess dropping constraints
will be more complicated in this case since one will have to check if other constraints are
using the same index.)

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