Le jeudi 31 janvier 2013 à 11:06 +0100, Pavel Stehule a écrit : > 2013/1/31 Vincent Veyron <vv.lists@xxxxxxxxxx>: > > > > Suppose I have a query of the form > > > > SELECT my_function(column_1), column_2 > > FROM my_table > > GROUP BY my_function(column_1) > > ORDER BY my_function(column_1); > > > > where my_function is a user defined function. > > > > How many times is the function computed? > > if function is stable or immutable, then once per row > In this post (watch for line-wrap) : http://www.postgresql.org/message-id/CAFj8pRAdYL1-hCxH +QSZQKHt9YnoaOiGkfX4cNc9mzUTimcs1w@xxxxxxxxxxxxxx you wrote that it is usually better not to mark SQL functions (as opposed to plpgsql functions). So should I mark SQL functions stable/immutable if I use them in a query like the one above, or is it unnecessary? -- Salutations, Vincent Veyron http://marica.fr/site/demonstration Logiciel de gestion des contentieux juridiques et des sinistres d'assurance -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
