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Date: Mon, 10 Nov 2008 11:11:44 -0800 (PST)
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-481-16-aa-dropFunction.diff

Attaching derby-481-16-aa-dropFunction.diff. Running tests now. This patch prevents you from dropping a function mentioned in a generation clause, per the spec.

The patch builds on the fact that generation clauses are implemented as a kind of default. Defaults, in turn, are a persistent object for which we already have good support in our dependency subsystem.

Touches the following files:

M      java/engine/org/apache/derby/impl/sql/execute/ColumnInfo.java

Adds dependency information to this  driving data structure.


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

Adds bind-time logic to fill the ColumnInfo with the dependencies of generated columns. These dependencies were already being identified but the information was being thrown on the floor.


M      java/engine/org/apache/derby/impl/sql/execute/DDLConstantAction.java
M      java/engine/org/apache/derby/impl/sql/compile/AlterTableNode.java
M      java/engine/org/apache/derby/impl/sql/compile/CreateViewNode.java

Adds execution-time logic to hammer the dependencies into SYS.SYSDEPENDS. The enforcement of the dependencies is handled by existing machinery in the dependency subsystem.


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

Adds 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, derby-481-16-aa-dropFunction.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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