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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-481) implement SQL generated columns
Date Fri, 14 Nov 2008 10:32:44 GMT

    [ https://issues.apache.org/jira/browse/DERBY-481?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12647571#action_12647571
] 

Knut Anders Hatlen commented on DERBY-481:
------------------------------------------

> - javadoc for StringUtil#stringify: would be nice to specify the format of
>   the output: Some such:
>
>   'null' | '[ ' [ <decimal int> { ', ' <decimal int> }* ] ' ]'

Except for the space after the opening bracket and before the closing
bracket, the format is identical to what you get from
java.util.Arrays.toString(int[]), which is not available prior to Java
1.5. Perhaps it's better just to document that it should return the
same as Arrays.toString() so that we can replace it with a call to the
standard library once we move to Java 1.5. Currently, the the method
is only used by test code, so maybe it should be moved out of the
production jars?

> - GeneratedColumnsTest#expectExecutionError: closing of ps is missing

Or even better: use BaseJDBCTestCase.prepareStatement() instead of
Connection.prepareStatement(). Then you get automatic cleanup in
tearDown().

> 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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