Ok, thanks a lot to all of you for your answers! (Always impressed by
the prompt feedback you get on this list!)
Quoting Gabriele Bartolini <Gabriele.Bartolini@xxxxxxxxxxxxxx>:
Ciao Dario,
On Tue, 21 Dec 2010 09:14:36 +0000, Dario Beraldi
<dario.beraldi@xxxxxxxx> wrote:
the query run better the planner is not able (allowed?) to create such
index, use it, and drop it once the query is done. Why is it so?
Because it is not its responsibility. This is the simplest and most
rational answer.
I would reply with some questions that hopefully will give you the
answer. How can you define a 'good' query from a 'bad' query?
Consider the case when an user launches a wrong query and the
planner you propose starts creating an index. I believe that would
be a mess.
Then ... how could you project this scenario in a concurrent context
where multiple users launch queries that 'need' an index?
I suggest that you look at the documentation for more information.
Otherwise, I strongly suggest that you read the chapter on the
planner from Greg's book on High Performance (which you can find
from here: http://www.postgresql.org/docs/books/)
Merry Christmas to you too!
Cheers,
Gabriele
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Gabriele Bartolini - 2ndQuadrant Italia
PostgreSQL Training, Services and Support
Gabriele.Bartolini@xxxxxxxxxxxxxx - www.2ndQuadrant.it
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Dr. Dario Beraldi
Institute of Evolutionary Biology
University of Edinburgh
West Mains Road
Edinburgh EH9 3JT
Scotland, UK
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The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.
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