Re: [Firebird-devel] Created: (CORE-3672) computed index by substring function for long columns

[Dmitry Y. <fir...@ya...>]

29.11.2011 12:35, Vlad Khorsun wrote:

> While i agree with you about SUBSTRING, i think the much better solution
> will be to allow to index COMPUTED BY columns. It allows to not compare
> potentially complex expressions at optimize time and to not write exactly
> same expressions in every query where such index is required.

Perhaps. And we have such a request in the tracker, AFAIR.

I'm just not really sure that adding a dummy column (that could never be 
selected from explicitly) to improve the performance looks like a proper 
approach. Surely computed columns don't add any extra overhead unless 
you select * from the table, but this still doesn't look elegant, IMHO. 
But that's just me, I'm not going to object seriously.


Dmitry