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From Daniel John Debrunner <...@apache.org>
Subject Re: Collation feature discussion
Date Sun, 18 Mar 2007 15:01:24 GMT
Mike Matrigali wrote:
> I'll let someone else summarize.  At this point I have
> been convinced by Dan that his proposal is the best way
> forward.  And by rick and dan that we should just go
> ahead and store column level metadata for the collate
> info in the store, as well as in the language level
> per column metadata.
> 
> The key points that convinced me are:
> o Even though we are proposing a "single" collation per
>   database, internally we need to support 2 per database to
>   do the right thing for system catalogs.  Once there are
>   2 we needed support in store to at the very least store
>   metadata per conglomerate.
> 
> o It looks like dan's proposal makes the runtime creation
>   of the collated and non-collated objects easier.  I don't
>   understand all the places this affects, but anything that
>   makes this easier seems good to me.

I think some design specification or notes would be really useful for 
collation. As Mike says the places where this has an impact are not well 
known, starting a list on a wiki page would be good, then others could 
look and ask if other areas are effected. E.g. I think the path we are 
heading down is that at create table or alter table add column time the 
collation for that column will be set in its DataTypeDescriptor, just 
like its nullability is today. Then at bind time when that column is 
referenced the collation type will be available through its DTD. But 
there are a host of other character expressions, it would be good to 
list these up front and how  the collation will be set, rather than 
discovering them one at time through coding (and missing some). E.g.
What's the defined behaviour for:

       string literal
       cast to character type of a character expression
       trim
       concatenation
       etc.

Then some writeup of how store column collation information is to be 
stored (along with upgrade issues) would really help cement a good 
design up front.

Thanks,
Dan.


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