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From "Alan Baldwin (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-1645) ALTER TABLE ... SET INCREMENT BY X... Turns off the "Generated By Default" identity column constraint
Date Wed, 27 Sep 2006 19:46:51 GMT
    [ http://issues.apache.org/jira/browse/DERBY-1645?page=comments#action_12438204 ] 
            
Alan Baldwin commented on DERBY-1645:
-------------------------------------

They are definitely closely related.   Same symptom, different version of Derby.  1495 was
logged against 10.1.3, 1645 was logged against 10.2.  Derby 10.2 introduced the "ALTER TABLE
WITH RESTART X" clause, and 10.1.3 did not have this.  That is the only real difference.

Disclaimer: I'm not familiar with the code base, but I'm guessing that one fix may solve both
issues.

> ALTER TABLE ... SET INCREMENT BY X... Turns off the "Generated By Default" identity column
constraint
> -----------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-1645
>                 URL: http://issues.apache.org/jira/browse/DERBY-1645
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.1.3.0, 10.1.3.1
>         Environment: Both Ubuntu Linux, Windows XP... Java 1.4.2_x and Java 1.5
>            Reporter: Alan Baldwin
>
> I have a table which has an auto-generated key:
> create table MyTable  (
>    TableId INTEGER GENERATED BY DEFAULT AS IDENTITY NOT NULL,
>    StringValue           VARCHAR(20)           not null,
>    constraint PK_MyTable primary key (TableId)
> )
> I verify that GENERATED BY DEFAULT is set:
> SELECT * FROM 
> sys.syscolumns col 
> INNER JOIN sys.systables tab ON col.referenceId = tab.tableid 
> WHERE tab.tableName = 'MYTABLE' AND ColumnName = 'TABLEID'
> I'm pulling in data for which I need to preserve the ID's:
> INSERT INTO MYTABLE (TableId, StringValue) VALUES (1, 'test1')
> INSERT INTO MYTABLE (TableId, StringValue) VALUES (2, 'test2')
> INSERT INTO MYTABLE (TableId, StringValue) VALUES (3, 'test3')
> In the absense of the Derby 10.2 feature (ALTER TABLE WITH RESTART X), I try to just
change the INCREMENT BY value and insert a row so that I can reset the "next" key value:
> ALTER TABLE MyTable ALTER TableId SET INCREMENT BY 50
> Then I insert a "dummy" record (which I will delete later...) to move the key upwards:
> INSERT INTO MYTABLE (StringValue) VALUES ('test53')
> However, I can now no longer insert explicit values into the primary key like this:
> INSERT INTO MYTABLE (TableId, StringValue) VALUES (-999, 'test3')
> I get this error:  SQL Exception: Attempt to modify an identity column 'TABLEID'. 
> Upon checking the sys.syscolumns table again, it verifies that the table no longer has
an auto-generated key, but the TableId is still an identity column.

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