Jan, On 01.11.30 02:19am, janI said: > 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.
Thanks for this tremendous work here. I'm still fighting with my
class and research project at 3:00am. ^^;
This server is a virtual machine. There is a limit to its CPU
power. And Andrea's suggestion is right. Join operations actually
creats a big n times m table first and then filter. That sucks when n
and m are both large.
>
> 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.
>>
>
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