On 2015-12-01 05:00, David Rowley wrote:
We already allow a SELECT's target list to contain non-aggregated columns
in a GROUP BY query in cases where the non-aggregated column is
functionally dependent on the GROUP BY clause.
For example a query such as;
SELECT p.product_id,p.description, SUM(s.quantity)
FROM product p
INNER JOIN sale s ON p.product_id = s.product_id
GROUP BY p.product_id;
is perfectly fine in PostgreSQL, as p.description is functionally dependent
on p.product_id (assuming product_id is the PRIMARY KEY of product).
This has come up before (on other forums, at least), and my main concern
has been that unlike the case where we go from throwing an error to
allowing a query, this has a chance to make the planning of currently
legal queries slower. Have you tried to measure the impact of this on
queries where there's no runtime gains to be had?
.m
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