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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-712) Support for sequences
Date Mon, 10 Aug 2009 15:07:15 GMT

    [ https://issues.apache.org/jira/browse/DERBY-712?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12741357#action_12741357
] 

Rick Hillegas commented on DERBY-712:
-------------------------------------

Hi Suran,

Thanks for the patch. Here are some answers to your question:

1) You don't need to add the permissions check which you saw in CREATE ROLE. The only permission
you need to worry about is the permission to create objects in the target schema. I address
that topic below.

2) The bind() logic is responsible for filling in the current schema name if the user doesn't
specify a schema. I address that topic below too.

Here is a quick review of CreateSequenceNode:

- I don't understand why initAndCheck() is called twice. I think that all you need is the
call which takes sequenceName as arg. But let me know your motivation for adding this line
if you think it is necessary.

- The header comment of bindStatement() should be revised. The main points of this method
are to resolve the schema name, determine privilege checks, and vet the variables in the CREATE
SEQUENCE statement.

- In bindStatement() you will want to resolve the schema name. Something like the following
should do the trick. This will verify that the schema name is valid (if specified) and if
the schema name is not specified, this will fill in the name of the session's current schema:

  sequenceName.bind( getDataDictionary() );

- If you add the following code to bindStatement() (after you have bound the schema name),
then a runtime check will be made to verify that the creator has permission to create objects
in the target schema:

  SchemaDescriptor sd = getSchemaDescriptor();

Thanks!
-Rick

> Support for sequences
> ---------------------
>
>                 Key: DERBY-712
>                 URL: https://issues.apache.org/jira/browse/DERBY-712
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>         Environment: feature request 
>            Reporter: Tony Dahbura
>            Assignee: Suran Jayathilaka
>             Fix For: 10.6.0.0
>
>         Attachments: altertable.diff, catalogs_a.patch, catalogs_b.patch, catalogs_c.patch,
catalogs_d.patch, catalogs_e.patch, catalogs_f.patch, catalogs_f_2.patch, catalogs_g.diff,
catalogs_h.diff, create_sequence_a.patch, SequenceGenerator.html
>
>
> Would like to see support added for sequences.  This would permit a select against the
sequence to always obtain a ever increasing/decreasing value.  The identity column works fine
but there are times for applications where the application needs to obtain the sequence number
and use it prior to the database write.  Subsequent calls to the table/column would result
in a new number on each call.
> SQL such as the following:
> SELECT NEXT VALUE FOR sequence_name FROM sometable ; would result in a next value.

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