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https://issues.apache.org/jira/browse/DERBY-481?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12580425#action_12580425
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rhillegas edited comment on DERBY-481 at 3/19/08 9:17 AM:
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Attaching a first rev of a functional spec for this feature:
GeneratedColumns.html
was (Author: rhillegas):
Attaching a first rev of a functional spec for this features:
GeneratedColumns.html
> 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
> Attachments: 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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