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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-481) implement SQL generated columns
Date Thu, 13 Nov 2008 23:52:44 GMT

    [ https://issues.apache.org/jira/browse/DERBY-481?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12647470#action_12647470
] 

Dag H. Wanvik commented on DERBY-481:
-------------------------------------

Reviewing patch derby-481-02-aa-utilities.diff.

Patch looks good to me. Some small notes:

- javadoc for StringUtil#stringify: would be nice to specify the format of
  the output: Some such:

  'null' | '[ ' [ <decimal int> { ', ' <decimal int> }* ] ' ]'

- GeneratedColumnsTest#expectExecutionError: closing of ps is missing

- GeneratedColumnsTest#assertResults
    :
    assertEquals( (expectedValue == null), rs.wasNull() );

    if ( expectedValue == null )    { assertNull( actualValue ); }

  Isn't the latter assert redundant after the first assert?

- GeneratedColumnsTest: lines > 80 long

- SQLState.java: it would look better to align the values for the new
  errors with the existing declarations (in column 72).

I didn't check the commented out new code much, since its not live yet.


> implement SQL generated columns
> -------------------------------
>
>                 Key: DERBY-481
>                 URL: https://issues.apache.org/jira/browse/DERBY-481
>             Project: Derby
>          Issue Type: New Feature
>          Components: SQL
>    Affects Versions: 10.0.2.1
>            Reporter: Rick Hillegas
>            Assignee: Rick Hillegas
>         Attachments: derby-481-00-aa-prototype.diff, derby-481-01-aa-catalog.diff, derby-481-02-aa-utilities.diff,
derby-481-03-aa-grammar.diff, derby-481-04-aa-insert.diff, derby-481-05-aa-update.diff, derby-481-06-aa-genreferences.diff,
derby-481-07-aa-noSQLinRoutines.diff, derby-481-07-ab-noSQLinRoutines.diff, derby-481-08-aa-castToDeclaredType.diff,
derby-481-09-aa-dummyDefaults.diff, derby-481-10-aa-foreignKeyActions.diff, derby-481-11-aa-notNull.diff,
derby-481-12-aa-padding.diff, derby-481-13-aa-alterDatatype.diff, derby-481-14-ab-dropColumn.diff,
derby-481-15-aa-renameAndAddDefault.diff, derby-481-16-aa-dropFunction.diff, GeneratedColumns.html
>
>
> Satheesh has pointed out that generated columns, a SQL 2003 feature, would satisfy the
performance requirements of Expression Indexes (bug 455). Generated columns may not be as
elegant as Expression Indexes, but they are easier to implement. We would allow the following
new kind of column definition in CREATE TABLE and ALTER TABLE statements:
>     columnName GENERATED ALWAYS AS ( expression )
> If expression were an indexableExpression (as defined in bug 455), then we could create
indexes on it. There is no work for the optimizer to do here. The Language merely has to compute
the generated column at INSERT/UPDATE time.

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