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https://issues.apache.org/jira/browse/DERBY-481?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rick Hillegas updated DERBY-481:
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Attachment: derby-481-14-ab-dropColumn.diff
Attaching derby-481-14-ab-dropColumn.diff. Running tests now. This patch
implements CASCADEd and RESTRICTed drops of columns which are referenced by
generated columns, per the spec. In short, if a generated column depends on the
column being dropped, then RESTRICT aborts the drop and CASCADE causes the
generated column to be dropped along with the original column. Makes the
following changes:
A) Reworks the implementation of the default descriptor so that it contains an
array of referenced column names rather than column positions. This eliminates
the need to remap those column positions when other columns are dropped.
B) Makes the drop column logic recursively call itself for generated columns
which depend on the original column being dropped.
Touches the following files:
M java/engine/org/apache/derby/catalog/DefaultInfo.java
M java/engine/org/apache/derby/catalog/types/DefaultInfoImpl.java
Changes to the default descriptor needed for (A).
M java/engine/org/apache/derby/impl/sql/compile/UpdateNode.java
M java/engine/org/apache/derby/impl/sql/compile/TableElementList.java
M java/engine/org/apache/derby/iapi/sql/dictionary/TableDescriptor.java
Accomodations for (A) in code which uses default descriptors.
M
java/engine/org/apache/derby/impl/sql/execute/AlterTableConstantAction.java
Reworks dropColumnFromTable() so that it calls itself on affected generated
columns.
M java/engine/org/apache/derby/loc/messages.xml
M java/shared/org/apache/derby/shared/common/reference/SQLState.java
New error message and warning.
M
java/testing/org/apache/derbyTesting/functionTests/tests/lang/GeneratedColumnsTest.java
New tests for ALTER TABLE DROP COLUMN scenarios involving generated columns.
> 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, 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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