Re: can/do indexes chain?

Charlie Mengler wrote:
>
> I've been asked to create an index which combines two fields, date & location.
> For reasons I don't really want to explain, we need/desire this index to
> be in the order of date, location. The minor gotcha is that while location
> will be populated at the time the record is created, the date field is not
> updated until a later point in time. This date is a document print date.
> So this date field will be going from a NULL value to a non-null value.
> I recognize that this can result in record chaining in the data table.
> In thinking about this, I realized this could have a similar affect
> within the index. However, I've never read anything about index chaining.
>
> Do/can indexes chain?
> Should I be concerned about this?
>
> --
> Charlie Mengler Maintenance Warehouse
> charliem_at_mwh.com 10641 Scripps Summit Ct.
> 858-831-2229 .NET? Not yet! San Diego, CA 92131

Charlie,

   For what I remember of B*Trees (not even the B*+%$# used by Oracle), indexes do not chain, they split. Since the date is the first column, updating it will totally reorder the index each time. I am currently wondering what would be the worst, between this and partitioning by range of date and allowing rows to migrate. Same kind of thing. It is likely to be very ugly. If this is possible, I'd rather drop the index, do the update, and recreate the index.

-- 
Regards,

Stephane Faroult
Oriole Corporation
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Author: Stephane Faroult
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