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From Tim Dudgeon <tdudg...@informaticsmatters.com>
Subject Re: drop column functionality
Date Wed, 23 Aug 2006 08:41:09 GMT


Bryan Pendleton wrote:
>> 1. Dropping the column seems very slow for large tables. 
> 
> This is good to know. I don't think anybody has really experimented with
> this yet. Can you quantify "very slow" with some real measurements
> you've taken? Do you think it would be reasonable to treat this as
> a follow-on improvement to the DERBY-1489 changes, or do you feel that
> the performance is so bad that DERBY-1489 is unusable as is?
> 
> I guess my assumption was that DROP COLUMN usage in large database
> scenarios would be rare, and that it would be more common for people
> to want to use DROP COLUMN during their initial application development,
> when tables are typically smaller. But perhaps this is a bad assumption?
> 
> If you think this would be reasonable to treat as a follow-on
> improvement, then please open a new JIRA issue for it, describe
> it as well as you can with the data you can provide, and link
> the new issue to DERBY-1489 so that we know they're related.
> 

I added some performance comparisons with Oracle to the JIRA issue.
http://issues.apache.org/jira/browse/DERBY-1489
This shows that Derby appears to be approx 3-4x slower at dropping a 
column in large tables.
I don't think this is a show stopper, but obviously any improvements 
would be of benefit.

Tim


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