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
