Thanks I did not know that LEFT JOIN and JOIN has different speeds on inodb tables. I made the fast fix, and split xmaint_uids into smaller tables, and is running now.
BUT I am dead nervous of deleting wrong data !! so the review in general would be nice. I have also decided to post the user list here, to give people a chance to shout and get removed from the list. There are very little margin for errors on our database, and I would not like to cause problems (I think I already have used this years allowance). Thanks for your suggestions, I will implement a couple of your ideas before I release the final script. Jan. On 29 November 2012 19:09, Andrea Pescetti <pesce...@apache.org> wrote: > On 29/11/2012 janI wrote: > >> ooo-wiki VM is so weak (compared to my notebook) that a lot of my >> "special" >> select/join statements timed out...and the just because I have a simple >> where clause "where user_id in (select user_id from wiki_maint_uids)" >> > > I only had a quick look yesterday and I cannot check now, but there were > several possible speed improvements, including using a simple JOIN instead > if a LEFT JOIN and then discarding NULL matches, introducing a primary key > or an index in the wiki_maint_uids table and using update on joins instead > of subqueries. I didn't test any of these, and I didn't see the database, > so don't trust the lines above too much! They are just semi-random thoughts > based on the code I saw yesterday, and it could turn out that these changes > slow down the queries instead of improving them. > > Regards, > Andrea. >
