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From Rick Hillegas <Richard.Hille...@Sun.COM>
Subject Re: Collation implementation WAS Re: Should COLLATION attribute related code go in BasicDatabase?
Date Thu, 15 Mar 2007 17:30:26 GMT
Daniel John Debrunner wrote:
> Rick Hillegas wrote:
>> Daniel John Debrunner wrote:
>>> ...
>>>
>>> - The collation type (the integer) is written into the meta-data for 
>>> an index just as ascending/descending is today (including the btree 
>>> control row, thus making the information available for recovery). 
>>> Collation type applies to all character columns in the index.
>>>
>> This suggests that all of the columns in the index must have the same 
>> collation? I don't think that is powerful enough to support the 
>> full-blown SQL collation language, which allows you to mix 
>> differently collated columns in an ORDER BY clause. Why can't the 
>> collation type be an array of ints just as the sort direction is an 
>> array of booleans in IndexDescriptor?
>
> That would be more flexible, but is it required?
I believe so. I don't see any rule which requires one collation for all 
of the character expressions in an ORDER BY clause. There does seem to 
be a rule requiring one collation for both sides of a comparison, e.g., 
for both sides of a < operator.

> Is an order by that spills to disk implemented using a BTREE?
I don't know the answer to this one.

Regards,
-Rick
>
> Thanks,
> Dan.
>


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