[erlang-questions] Getting attributes

Toby Thain <>
Sun Oct 14 22:43:39 CEST 2012


On 14/10/12 3:38 PM, Dmitry Kolesnikov wrote:
> Toby,
>
> Unfortunately, composite index on (x,y) does not give you an optimal performance due to B-Tree index nature. Any (x,y) proximity requests are converted into random disk I/O because B-Tree clusters data first component  and then by second. This is a reason why z-order curve were invented. It allows to fit spacial data into B-Tree index and provide you sequential disk I/O for proximity queries.
>
> - Dmitry
>
>

A good point about locality. Does the OP require this level of 
performance, though? There is probably low hanging fruit before one gets 
to the point of tuning RDBMS index types.

--Toby



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