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From Daniel John Debrunner <...@apache.org>
Subject Re: how should store get an object based on format id and collation id?
Date Tue, 17 Apr 2007 14:36:48 GMT
Mike Matrigali wrote:
> 
> 
> Daniel John Debrunner wrote:


>> I'd assumed that every time a collation was needed that enough meta 
>> data was available to determine the collation. For example with 
>> language based comparisons the collation will be known at compile time 
>> and thus can be used. For index based collation the metadata must be 
>> available already today because the collations must be using the 
>> asc/desc flag.
>>
>> Assuming that is true, then no need to store the collation in the 
>> DVD/SQLChar
> Can you explain more about how this would happen.  Currently a path
> through store goes:
> 
> 1) empty dvd created
> 2) dvd initiated from disk
> 3) dvd is compared to other dvd's created by step 1 and 2.  Step 3
>    can happen many times reusing one dvd and changing the other
>    dvd multiple times (ie. a search of the tree in index).
> 
> I was assuming store would input correct collate at step 2 and then 
> compare happens using collation alred set up to do compares in step 3.
> 
> I am guessing you want no input of collate info at step 2 but some 
> change at step 3, but not sure what. 

If the collation is available at step 2 then yes it should be used to 
create the required dvd. I thought there were cases when the collation 
was not available?

> Do want step 3 to create yet
> a different dvd?  

I think step 3 would only create a different dvd (and only for the first 
compare in that query) if in step 2 no collation type was available.

> I was hoping for collation to be hidden from store within the datatype
> rather than exposed on every compare call.

Great if that's possible, but it doesn't match what is going on today. 
Currently how the column is collated is exposed on every compare, 
through the asc/desc flag. Since that is occurring I didn't think it 
would be an issue for the collation type to be available.

Dan


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