Optimization of unnecessary GROUP BY columns

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От Kevin Murphy
Тема Optimization of unnecessary GROUP BY columns
Дата
Msg-id 459156F4.7050207@genome.chop.edu
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Ответы Re: Optimization of unnecessary GROUP BY columns  (Martijn van Oosterhout <kleptog@svana.org>)
Список pgsql-general
When columns are required in a GROUP BY clause even though some of them
are fully dependent on others, is there any plan for making it possible
to do the GROUP BY only on the necessary columns?  The 8.X documentation
made me curious:

Section 7.2.3 in the 8.X documentation ("The GROUP BY and HAVING Clauses"):

"SELECT product_id, p.name, (sum(s.units) * p.price) AS sales
FROM products p LEFT JOIN sales s USING (product_id)
GROUP BY product_id, p.name, p.price;
...
Depending on how exactly the products table is set up, name and price
may be fully dependent on the product ID, so the additional groupings
could theoretically be unnecessary, but this is not implemented yet."

-Kevin Murphy


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