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From "Satheesh Bandaram (JIRA)" <derby-...@db.apache.org>
Subject [jira] Updated: (DERBY-392) Disable creating indexes on long varchar for bit data. Long varchar column doesn't allow creating indexes already.
Date Fri, 01 Jul 2005 05:44:58 GMT
     [ http://issues.apache.org/jira/browse/DERBY-392?page=all ]

Satheesh Bandaram updated DERBY-392:
------------------------------------

    Attachment: patch

Submitting a patch for review. I think we need to document that Derby doesn't support indexing,
group by, order by on long varchar for bit data anymore in release notes, in case some one
is already using this incorrect behavior.

I think it would be good to port this fix to 10.1, so we can prevent more incorrect dependence
on this behavior.

> Disable creating indexes on long varchar for bit data. Long varchar column doesn't allow
creating indexes already.
> ------------------------------------------------------------------------------------------------------------------
>
>          Key: DERBY-392
>          URL: http://issues.apache.org/jira/browse/DERBY-392
>      Project: Derby
>         Type: Bug
>   Components: SQL
>     Versions: 10.0.2.2, 10.1.1.0
>  Environment: generic
>     Reporter: Satheesh Bandaram
>     Priority: Minor
>  Attachments: patch
>
> I guess I did not articulate my reasons for suggesting removal of index support for 'long
varchar for bit data' completely.
>  
>     1) Long varchar types are not comparable... If they are not comparable, it should
not be possible to use them in GROUP BY, ORDER BY or allow regular B-Tree indexes.
>    2) Also, long varchar types tend to be long in size and hence the regular B-Tree mechanism
is not a suitable way to index them. Dan also mentioned they become ineffective for keys longer
than half a page size.
> It should not be possible to create an index on 'long varchar for bit data' datatypes.
Derby currently doesn't allow creating indexes on 'long varchar' datatypes and the same should
apply for it's bit data equivalent too.
> ij> create table longchar ( i int, c long varchar);
> 0 rows inserted/updated/deleted
> ij> create index longIdx on longchar(c);
> ERROR X0X67: Columns of type 'LONG VARCHAR' may not be used in CREATE INDEX, ORD
> ER BY, GROUP BY, UNION, INTERSECT, EXCEPT or DISTINCT statements because compari
> sons are not supported for that type.
> ij> create table longcharBitData ( i int, c long varchar for bit data);
> 0 rows inserted/updated/deleted
> ij> create index longIdx on longcharBitData(c);
> 0 rows inserted/updated/deleted
> Derby also seems to allow GROUP BY and/or ORDER BY on LONG VARCHAR FOR BIT DATA types.
I believe this is incorrect too.
> select c from longcharBitData group by c;
> C
> --------------------------------------------------------------------------------
> ------------------------------------------------
> 0 rows selected
> ij> select c from longcharBitData group by c order by c;
> C
> --------------------------------------------------------------------------------
> ------------------------------------------------
> 0 rows selected

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