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https://issues.apache.org/jira/browse/DERBY-481?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12647466#action_12647466
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Dag H. Wanvik commented on DERBY-481:
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I read the specification again, clear and easy to read!
Some notes:
- Overview
2nd sentence. Maybe add ALTER TABLE as well.
3rd sentence. "The user declares" -> "The user can declare"
- SQL standard:
Add sections 11.8, 11.39
Reference to section 14.18 should be to 11.18, I think
- syntax:
generation-clause ::= GENERATED ALWAYS ( value-expression )
************************************* "AS" keyword required after ALWAYS but
missing
- SYSCOLUMNS:
no new column was added, so I guess this section should be modified to
reflect the implementation now?
- Documentation
If we decide REVOKE execute privilege from <role> will impact functions
references in generated columns (as in dropping them), this should probably
be documented
along with the new doc for REVOKE <priv> from <role> and DROP
<role>.
Add note in INSERT on the use of "default", perhaps?
Appendix A: Possibly Non-deterministic System Functions
- add CURRENT SCHEMA
- add CURRENT SQLID
> 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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