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Date: Thu, 30 Oct 2008 08:19:44 -0700 (PDT)
From: "Rick Hillegas (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Updated: (DERBY-481) implement SQL generated columns
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     [ https://issues.apache.org/jira/browse/DERBY-481?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

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

    Attachment: derby-481-06-aa-genreferences.diff

Attaching derby-481-06-aa-genReferences.diff. This patch makes it illegal for generated columns to reference other generated columns, per the functional spec. Running regression tests now.

Touches the following files:


M      java/engine/org/apache/derby/impl/sql/compile/ResultColumnList.java
M      java/engine/org/apache/derby/iapi/sql/dictionary/TableDescriptor.java

Adds some small helper methods to assist the machinery in TableElementList.bindAndValidateGenerationClauses.


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

Adds logic to raise an exception if a generation clause mentions generated columns.


M      java/engine/org/apache/derby/impl/sql/compile/AlterTableNode.java
M      java/engine/org/apache/derby/impl/sql/compile/CreateTableNode.java

Adds new argument to calls to TableElementList.bindAndValidateGenerationClauses.


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

Adds new error message raised when generation clauses reference generated columns.


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

Adds tests for this behavior. While I was in there, I added tests to verify some other functionality: generation clauses can't reference other tables or run subqueries.


> 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, 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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