Re: Faster distinct query?

On 9/22/21 16:20, David G. Johnston wrote:
> I'd probably turn that index into a foreign key that just ensures that 
> every (station,channel) that appears in the data table also appears on 
> the lookup table.  Grouping and array-ifying the lookup table would be 
> trivial.  Either modify the application code or add a trigger to 
> populate the lookup table as needed.


I fully agree with this. Adding a trigger to populate a lookup table is 
a standard design in situations like this. Using "DISTINCT" almost 
always spells trouble for the performance.


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Mladen Gogala
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