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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-481) implement SQL generated columns
Date Wed, 19 Nov 2008 00:19:44 GMT

    [ https://issues.apache.org/jira/browse/DERBY-481?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12648832#action_12648832
] 

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

Reviewed derby-481-07-ab-noSQLinRoutines. Good patch, verified that
the extended test fails without the rest of the patch. Notes:

M      java/engine/org/apache/derby/impl/sql/compile/QueryTreeNode.java

- throwReliabilityException: new argument fragmentBitMask lacks @param

M      java/engine/org/apache/derby/impl/sql/compile/StaticMethodCallNode.java

- You have used the reliability constant SQL_IN_ROUTINES_ILLEGAL.
  Isn't the name "routines" that overly wide here, since only functions are
  ever allowed in generation clauses?


> 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, derby-481-17-aa-currentSchema.diff,
GeneratedColumns.html, 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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