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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-481) implement SQL generated columns
Date Mon, 10 Nov 2008 14:31:49 GMT

     [ https://issues.apache.org/jira/browse/DERBY-481?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Rick Hillegas updated DERBY-481:
--------------------------------

    Attachment: derby-481-15-aa-renameAndAddDefault.diff

Attaching derby-481-15-aa-renameAndAddDefault.diff. Tests ran cleanly for me. Committed at
subversion revision 712664.

This patch makes two changes, per the spec:

A) Prevents users from renaming columns which are referenced by generation clauses.

B) Prevents users from using ALTER TABLE to add defaults to generated columns. Note that the
parser already prevents you from adding defaults to generated columns via CREATE TABLE.

Touches the following files:

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

Raises an error if you try to rename a column referenced by a generation clause.


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

Raises an error if you try to add a default to a generated column.


M      java/engine/org/apache/derby/loc/messages.xml
M      java/shared/org/apache/derby/shared/common/reference/SQLState.java

New error messages for the newly forbidden conditions.


M      java/testing/org/apache/derbyTesting/functionTests/tests/lang/GeneratedColumnsTest.java

New test cases.


> 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, 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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