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From "Uriah Eisenstein (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-4831) Support for auto-calculated (virtual) columns
Date Mon, 04 Oct 2010 08:13:33 GMT
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: 10.6.1.0
            Reporter: Uriah Eisenstein


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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