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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4379) Let´s add comments to Derby
Date Thu, 17 Sep 2009 09:02:57 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12756425#action_12756425
] 

Knut Anders Hatlen commented on DERBY-4379:
-------------------------------------------

It sounds like a useful feature to me. Adding reserved words that are not reserved in the
standard sounds unattractive because it makes it harder to port applications to Derby and
may also break existing applications using Derby. Perhaps we could add system procedures instead?
Something like:

CALL SYSCS_UTIL.SYSCS_COMMENT_ON_TABLE('MYSCHEMA', 'MYTABLE', '...');
CALL SYSCS_UTIL.SYSCS_COMMENT_ON_COLUMN('MYSCHEMA', 'MYTABLE', 'COL1', '...');

I don't think we have a free slot in which to store comments currently, but it should be easy
enough to add comment columns to some of the system tables (like SYS.SYSTABLES and SYS.SYSCOLUMNS).

To change the system tables and add new system procedures, these two classes should be a good
starting point:

org.apache.derby.catalog.SystemProcedures
org.apache.derby.impl.sql.catalog.DataDictionaryImpl

The different system tables and their columns are documented here: http://db.apache.org/derby/docs/dev/ref/rrefsistabs38369.html

> Let´s add comments to Derby
> ---------------------------
>
>                 Key: DERBY-4379
>                 URL: https://issues.apache.org/jira/browse/DERBY-4379
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 11.0.0.0
>         Environment: N/A
>            Reporter: Rami Ojares
>             Fix For: 11.0.0.0
>
>
> I could not find any previous issue about adding comments to Derby.
> I found one suggestion about it on the web somewhere but not here in Jira.
> DB2 and Oracle seem to have a separate COMMENT ON clause
> Eg.
> COMMENT ON TABLE EMPLOYEE IS 'Reflects first quarter 2000 reorganization'
> COMMENT ON COLUMN mytable.primarykey IS 'Unique ID from Sequence SEQ_MASTER'
> MySql on the other hand has a more compact syntax
> CREATE TABLE FOO (A COMMENT 'This col is A')  COMMENT='And here is the table comment'
> I quess SQL standard does not talk about commenting objects like tables columns etc.
(Although I am not sure, maybe someone could prove me wrong here).
> So I propose we start with syntax like
> CREATE TABLE TBL_NAME (<coldefinition> COMMENT 'colcomment' ...) COMMENT ' tablecomment'
> Column comment could appear anywhere where Column-level-constraint can and the same would
apply for table comment.
> View comment could come after the query in view definition.
> We would only need to add reserved word COMMENT. (Although it is a common word and most
certainly is used by someone as a column or tanle name).
> It might be that there is already a spot for comments (or should we say remarks) because
the DatabaseMetadata returns a column with that name for every attribute.
> It is always empty now.
> This feature could take the self-documenting property of derby databases to the next
level.
> I could code this feature but now I would like to know what people think about this issue
in here and since I have not been coding Derby before then perhaps a few pointers would be
helpful from someone who knows the soucecode of Derby well.

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