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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DERBY-4831) Support for auto-calculated (virtual) columns
Date Fri, 28 Sep 2012 18:27:07 GMT

     [ https://issues.apache.org/jira/browse/DERBY-4831?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Mamta A. Satoor updated DERBY-4831:

    Urgency: Low
     Labels: derby_triage10_10  (was: )
> Support for auto-calculated (virtual) columns
> ---------------------------------------------
>                 Key: DERBY-4831
>                 URL: https://issues.apache.org/jira/browse/DERBY-4831
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions:
>            Reporter: Uriah Eisenstein
>              Labels: derby_triage10_10
> The suggestion is similar to generated columns, but with the column value not actually
stored in the database, but rather recalculated whenever the column is accessed.
> This saves storage space in return for additional processing.
> It is also suggested to support creating indices on the calculated columns; this could
be a partial solution to expression-based indexes (Derby-455). For instance, creating an index
on an expression such as "upper (column)" requires Derby to recognize the expression in a
query involving the column, so that it could take advantage of the index; this could be difficult
for more complex expressions. Using a generated column would double the required storage for
the original column. An auto-computed column could solve both problems.
> (I don't know if there is any standard SQL syntax for defining such columns)

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