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From Daniel John Debrunner <...@apache.org>
Subject Re: [jira] Updated: (DERBY-2524) DataTypeDescriptor(DTD) needs to have collation type and collation derivation. These new fields will apply only for character string types. Other types should ignore them.
Date Wed, 04 Apr 2007 18:52:46 GMT
Mamta A. Satoor (JIRA) wrote:

> Questions
> 1)I have included all the constant definitions related to collation in TypeDescriptor.
> If anyone has suggestion on a better place to define them, let me know.

I'd thought about defining such constants on StringDataValue since they 
only apply to character types.

Why string constants for derivation though, why not integer values?
Also there's no constant for error, though I would not recommend having 
an error value. Why not just use none as the default value? That will 
lead to the same behaviour, no collation suppported. Adding an error 
state is something that is not in the SQL standard.

Note that the javadoc comments you added for these constants are only 
for the first constant, the others will have no javadoc.

> 2)Is it right to assume that readExternal and writeExternal methods in
> TypeDescriptorImpl will get called only for persistent columns?

Probably, though looking forward at some point the derivation will need 
to be stored, might be worth thinking about this now to avoid future 


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