Support for auto-calculated (virtual) columns
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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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