Hello 2013/1/18 Robert James <srobertjames@xxxxxxxxx>: > I'd like to understand better why manually using a temp table can > improve performance so much. one possible effect - there should be different statistic did you look on EXPLAIN ANALYZE? Regards Pavel Stehule > > I had one complicated query that performed well. I replaced a table > in it with a reference to a view, which was really just the table with > an inner join, and performance worsened by 2000x. Literally. > > I then modified it to first manually SELECT the view into a temp > table, and performance returned to close to the original query. The > temp table had the same indexes as the original one. > > How is that? What does the temp table do that the planner can't do > itself? Don't planner uses temp structures too? > > In other words: Since my query is 100% identical algebraicly to not > using a temp table, why is it so much faster? Why can't the planner > work in the exact same order? > > > -- > Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
